Igneous rock

/ 05/01/2022

Rock, rock, rock

There are only three types of rocks. This may be surprising, seeing no two rocks are the same and geologists use a never-ending series of names for these rocks, from abelsonite to zykaite. Names are what makes geology so hard. Henrik has written about gem stones, in a highly recommended post. But here I want to look broader.

There are only three types of rocks. They differ in how they were formed. As you may imagine, it is not easy to form a rock. Grabbing a hand full of sand and squeezing won’t do. You either need to apply much more pressure (something like the weight of a mountain) or much more heat (sufficient to melt the sand). The Earth has solved the problem in three different ways.

Left: metamorphic rock (schist); middle: igneous rock (granite); right: sedimentary rock (banded iron formation)

The first is by taking an existing rock and subjecting it to high temperature and pressure. This can do two things: the rock becomes soft and deforms, and the minerals can change into another form. The rock metamorphoses: it is now a metamorphic rock. Examples are slate and marble.

The second is by sedimentation. The process breaks up existing rock, either by erosion or by dissolution followed by the reverse process, chemical precipitation. The fragments are brought together by wind or sea. Once a deep layer of sediment has accumulated, the pressure can push the particles together. This is sedimentary rock. Examples are shale, chalk and sandstone.

The third is by melt followed by solidification. This happens in volcanoes, and produces igneous rocks. They may be intrusive, meaning that that they remain below ground, or extrusive, meaning that they erupt as lava and solidify on the surface. Examples are basalt, rhyolite and (for specialists) gabbro. As this is a volcanic blog, I will focus here on these igneous rocks.

Naming

Igneous rocks are named for the minerals (composition) and the size of the crystals or grains they contain. The graininess shows at what depth to magma solidified. Surface flows (lava) cool fast, and the grains have little time to grow: the crystals are small and the rock is fine grained. Deeper magma cools slow and forms larger crystals: medium-sized grains form at intermediate depth (dikes and sills) and large grains (coarse-grained rock) forms at large depth, typically in deeper magma chambers.

There is a large variety of minerals. Silicates contain silicon and oxygen. Olivines and pyroxenes are silicates containing magnesium and iron. They are also described as ‘mafic’. If it contains mainly magnesium it is an olivine, if mainly iron it is a pyroxene. The green beach of Hawai’i has olivine sand: I keep some (legally bought!) in my office. If it also contains calcium or sodium it becomes hornblend; this is a member of the amphiboles, a large group of minerals which are in effect an olivine or pyroxene with something added. The iron and magnesium can be replaced by aluminium. Silicates which contain aluminium, sodium, calcium and (or) potassium are known as feldspars, also described as ‘felsic’. A feldspar with sodium and potassium but no calcium is known as an alkali feldspar. A feldspar with aluminium together with sodium and calcium but no potassium is a plagioclase. They can have different amounts of calcium and sodium. A plagioclase with calcium but no sodium is called a calcium feldspar, or anorthite, but it is still a member of the plagioclase family. If it contains sodium but neither calcium nor potassium it is a sodium feldspar, also known as albite. (The name is based on its colour.) Albite falls at the intersection of alkali feldspars and plagioclase and strictly speaking is a member of both families – or of none. Finally, quartz is formed from SiO2.

Mineral

Composition

silicate

Si, O

olivine

silicate + Mg

pyroxene

silicate + Fe

amphibole

silicate + Mg/Fe/Ca/Al + OH/F/Cl

hornblend (an amphibole)

silicate + Mg/Fe/Al + Ca/N + OH/F

biotite (an amphibole)

silicate + Mg/Fe/Al + K + OH/F

feldspar

silicate + Al + N + K/Ca

plagioclase (a feldspar)

silicate + Al + N/Ca

alkali feldspar

silicate + Al + N/K

albite (a feldspar)

silicate + Al + N

(Here, ‘N’ stands for sodium (or natrium) and ‘K’ for potassium (or kalium).) We can now see how several igneous rock types are related. The columns show the common compositions, while each row is for a different size of the grains contained in the rocks

I. olivine + pyroxene

II. pyroxene + plagioclase

III. Alkali feldspar + pagioclase

IV. Quartz + alkali feldspar

fine grained (volcanic rocks)

komatiite

basalt

andesite

rhyolite

medium grained (sills/dikes)

(micro-peridotite)

dolerite

(micro-diorite)

(micro-granite)

coarse grained (magma chambers)

peridotite

gabbro

diorite

granite

Group I is a rare type, formed from pure mantle material and found only in extreme oceanic crust. Group II forms oceanic crust: basalt in the upper part and gabbro in the deeper crust. Groups III and IV are magmas that themselves came from melted oceanic crust. These magmas create continental crust in the process. There are intermediate types between the columns, for instance dacite is intermediate between andesite and rhyolite; granodiorite is the coarse-grained form of this rock. The oldest rock known on Earth is a granodiorite, found in Greenland and dated to 4.1 billion years ago. There is also variation within each column, for instance diorite can contain mainly alkali feldspar or plagioclase, or contain a mixture of both families.

Periodite

Formation

The different groups are in part determined by the magma temperature. The various minerals have different melting temperatures. When magma cools, each mineral will become solid at its own temperature. What is left in the magma are all the minerals that have not yet solidified. This is known as the Bowen sequence. It shows how a very cool magma will consist only of molten quartz, while a magma containing liquid olivine must be very hot.

The Bowen sequence. Source: wikipedia

This is also the reason that magmas from molten oceanic plates are different from those from the mantle. Mantle melt formed the ocean floor, but some of the minerals had dropped out, especially olivine. The oceanic plate formed from what was left. Volcanoes along a subduction zone obtain their melt from the subducting plate. But this lacks the minerals with the highest melting temperatures as they were never in the oceanic plate. Further evolution of the magma can take place as it ages and cools. Subduction volcanoes, the main builders of island arcs and continents, erupt this new mixture. As the highest density minerals have been removed, the crust it creates has lower density. This makes the continents rise above the ocean. (Of course, humanity is busy trying to reverse this and make the ocean rise above the continents.)

There is much more to say about this. The melt and crystallization can form amazing minerals. Again Henrik should be given the last word on this: Mineralisation processes.

Intrusion

Adapted from wikipedia. The various greens are the original greenstones. The pink area is the granite intrusion. Erosion later removed the rock above the red line. This left an inner core of granite, surrounded by vertical layers of older greenstone.

We now have a continental crust, and for some reason magma begins to collect below. This can come from an oceanic plate below or from melting of the bottom of the continental plate. The melt has lower density than the solid material and rises, but it has higher density than most of the continental plate so it only rises so far. A large collection of melt collects at that depth. A large volume of melt at depth is called a batholith. The batholith may evolve, and as it cools the remaining melt is lower density and it wants to rise. To do so, it has to push the overlying rock out of the way.

The picture shows what happens. The rock is split and the melt rises past the rock. A dome forms which deforms the original rock. In extreme cases the horizontal layers of the surrounding rock become vertical, alongside the intruding magma. We now have an intrusion .

The intrusion may or may not erupt. In either case, what is left underground will eventually solidify, often as a granite or granodiorite but this depends on how the melt formed in the first place.

Erosion now destroys what was created. The dome is removed, and the top layers of the old surface are gone. The red line indicates an imaginary erosion level. At this red line, we see the intrusion in the centre, surrounding by the layers of the original rock. The layers become younger as we move further from the intrusion.

Barberton, South Africa

Barberton, Mpumalanga, South Africa

Southern Africa is build on some of the oldest rocks that are known. Not quite the oldest: Greenland predates it by perhaps half a billion years. But it has the advantage that far more of the ancient rock survives. That is due to a geological accident: Souther nAfrica has remained remarkably well insulated from the rest of the world. In the dance of the continents it remained true to itself, sometimes shuffling against others, sometimes caught by the crowd but always keeping its core identity intact. South Africa advertises itself as the world in a country, with some justification. It also has kept the history of the world. But there are scars. One of those scars is the Drakensberg, formed when a supercontinent split and took a bit of Southern Africa with it. Parts of the Kaapvaal craton are now found in Australia, Madagascar and India, as well as East Antartica and the Falklands. Much has been lost, but much has survived. The ancient heart of the craton can still be seen in the rocks around Barberton, formed when the world was new and the first mini-continents put their heads above water. It shows us how the pillow lavas became river deltas. The oldest rocks here are a granodiorite, with a grey-green colour. Where they reach the surface they are known as a greenbelt, as is the case around Barberton. Here, the rocks are between 3.0 and 3.6 billion years old.

The ancient rocks became deeply buried by younger rocks: sediment and flood basalts, and by later intrusions which formed a granite layer above the old greenstone. These protected the ancient core against erosion. The overlying rocks took forever to erode. Only now have they revealed what lies below. But only in a small area around Barberton. Elsewhere they remain buried under a protective cover. Where they are revealed there is a sharp contrast between the grey-green ancient rock and the pink granite intrusion. The ancients did not survive entirely unscathed. They have been folded: layers that were horizontal when first formed may be vertical now, caused by the granite intrusions which forced themselves into and through the greenstone rocks and deformed them in the process. The granite intrusion has been dated to 3.0 to 3.2 billion years ago.

Road cutting at Pigg’s Peak in Swaziland. The grey rock is one of the oldest rock in Africa, a granodiorite formed from calcium feldspar and quartz, dated to 3.644 billion years ago, which formed in proximity to a greenstone. (More correctly it has metamorphed into a gneiss.) The pink(ish) rock is a younger granodiorite from a pagioclase that intruded into the older rock, dated to 3.07 billion years ago. (More correctly it is a feeder dike for the intrusion that formed the Pigg’s Peak batholith.) Photo by Carl Anhaeuser

The Barberton greenstone belt

The Barberton greenstone belt

The figure shows the (simplified) geological map of the region. The three groups are ordered from younger to older. The oldest is the ‘onverwacht group’, formed by volcanic activity. It contains komatiite, followed by a seafloor sediment layer, followed by basalt. It seems to trace the development of an island arc, from the formation of the oceanic crust to its recycling, at magma temperatures a bit higher than currently found. the Fig Tree group is a sandstone which formed later. Finally, the Moodies group is a sediment that formed in a shallow, tidal basin. The pinkish rock is the intrusion, on either side of the belt. It made the different layers vertical, with the oldest rocks closest to the intruding rocks.

The intrusion has a different composition to the original green belt. The ancient rock contained pillow lavas, erupted in the deep sea. It contains komatiite, showing that the magma was supplied by a hot mantle, in a rift (it is difficult to call it a mid-oceanic rift when the entire world was one ocean without land). The intrusion is granitic: it was fed by subduction melt. The world was changing, continents were taking shape and new type of volcanoes formed.

One of those volcanoes still remains. That is another story. Keep posted.

Albert, January 2022

Some of the photos and quite a bit of the information is from the book ‘Earth & Life’ by Terence McCarthy and Bruce Rubidge

For more on the topics of rocks, see Lava rocks

Related posts

171 thoughts on “Igneous rock”

  1. I remember reading in a book once that the first continent, called Ur, managed to survive intact inside later continents and supercontinents right up until the breakup of Pangea. That is why South Africa (and also much of Australia) preserves so much ancient crust. It is quite remarkable really, 3 billion years to break up only in the most recent cycle.

    There has also been a new flurry of earthquakes at Fagradalsfjall, and Kilauea has resumed erupting again 🙂

    • It was intact inside Gondwana. A bit of Australia was attached to the original Kaapvaal craton: debris from the same impact has been found in both. India and Madagascar would have joined much later. East Antartica – who knows. Full-fletched continents probably did not form until about 2 billion years ago. The first known collision strong enough to create thick continental crust is about 2.7 billion years ago, attaching Zimbabwe to Kaapvaal. Before that, the cratons were effectively large islands and collisions not that frequent. Plate tectonics may have changed when the continents grew large enough to affect the mantle temperature below them. I wonder whether that was the cause of flurry of continental collisions around 2 billion years ago, seen on all cratons. I doubt that they had formed a supercontinent.

      • The Rise of large continents may have caused the arrival of catastrophic flood basalt continetal breakups, as the larger landmasses insulates the mantle. Continents grows by Sillica rich plutonic magmatism at subduction zones, granite subduction magmatism been very active through the archean.

        Accreation of continents by subduction granite magmatism and plutonism.

        Albert How large will the sillecous continents grow? Earth have still a powerful internal heat engine being the largest terestrial planet in this solar system. Tectonics and Subduction Will keep going for perhaps 2,5 billion years more.

        In Early Archean it was Hyperactive chaos tectonics in an almost competely oceanic world

        • That is a good question. Continents now cover about a third of the earth. We already have the situation where oceanic plates move below continents even though they are too young to subduct: that happens in the western north America. It will become more common and could cause more volcanism on land. But new land is mainly created via island arcs, i.e. subduction zones inside oceans. That still happens. Oceanic LIPs do not create much new land: they form basalt which will subduct with the rest of the plate. Island arcs at the moment are about 1.5% of all land area. Say a subduction zone lasts for 50 million years, in which case you add 1.5% per 50 million years. That is 30% per billion years. It is an overestimate as the main island arc is Indonesia, but much of it is actually on an old continent. With this number I get that in a billion years a little less that half of the world is continent. More land means sea has to rise, so more of these continents would be flooded. The average continent is about 500 meters high. Decreasing the seas by this much requires a sea level rise of 600 meters or so. (I have included the correction for the weight of the water which will push the ocean floors down by some 300 meters.) So at this point much of the continents are flooded and land area (which is different from continents) will actually go down. Interesting.

          • Kind of seems like the early earth was an ocean planet because the crust was more uniform, parts began to thicken and form land, but as the new crust expands it will eventually force the ocean back to the original configuration just with thicker crust. We live in a time of transition.

            Probably will not get to happen but if the whole crust becomes granitic it could be very hard for basaltic volcanism to happen, though a lot of silicic calderas would exist, VEI 8s might be more common in the future.

      • Very intresting, How large will the continents become in the future? They have certainly grown alot since the archean.

        • I would guess continents will keep growing until they are so big plate tectonics doesnt really work efficiently anymore, then we get a situation more like Venus with active tectonics but no proper plates so to speak, and probably huge scale volcanism as the heat is trapped. Earth is big enough it will never cool down before it is destroyed, not to the extent volcanism is extinguished.

          I think in the above scenario there would still be significant ocean crust, but if there is more than half continent then said continents would always be running into each other, not dispersing and recombining as they do now.

          The question is if this will happen before the sun gets too hot. If the crust gets stagnant then there is a time limit, the next episode of rifting will be apocalyptic, flooding the planet with lava, and in all likelyhood rendering it permanently uninhabitable. Desert planets with active volcanism are probably not long lived, Venus was one a billion years ago, then it flooded itself, with so much water vapor in its atmosphere as well as CO2, its surface probably heated up to over 1000 C, hence the 6000 km long lava channels, that is extreme even for the most absurd of flood basalts, there must have been a helping hand. This was at the same time complex life was evolving too just before the Cambrian explosion, not some distant era in the planets formation. Most climate models say the sun will get too hot in a bit over a billion years but the planet might well do the job itself before that…

          • I think we should be thankful to this beautiful blue ball in which we live in many ways. Either plate tectonics or the high water content in Earth’s magmas regulate volcanic activity a lot. Terrestrial volcanism is very mild compared to its neighbours.

            Mars can go dormant or with very little volcanic activity for hundreds of millions of years and then unleash an apocalyptic volcanic episode. For example the last phase of activity of Tharsis which took place sometime 100-200 million years ago which built Olympus Mons and reactivated four other pre-existing volcanoes. Mars has been dormant ever since except for two isolated flood eruptions from giant dykes in Cerberus Fossae.

            Some crater counting estimates put the surface of Venus as being 450 million years old and having formed all at about the same time. It is difficult to know if really all of the surface has the same age though because Venus only has large impact craters. Only the largest meteorites can survive an impact against the atmosphere of Venus. This is unlike Mars which has small impact everywhere making it much easier to date its surfaces, even small areas.

            In any case if the whole surface of Venus was really formed 450 million years ago then it must have been a true volcanic apocalypse. With hundreds of very powerful flood basalt-scale volcanoes erupting all over the planet, giant dykes scarring the surface, and massive lava flows eroding canyons into the ground. It is no wonder that Venus is an inferno planet then.

            I think though that even if plate tectonics stop Earth will not become the same way as Mars or Venus, at least not immediately. It will probably take hundreds of millions of years to build up for such a volcanic apocalypse and even then perhaps Earth doesn’t have the conditions to pull off something like that. I suspect that Earth’s mantle is higher in volatiles compared to Mars. As far as I’ve seen Martian eruption as almost all of them purely effusive, more effusive even that Hawaii. The gas might help keep volcanic activity going on in Earth, although this is just an speculation of mine.

          • Yes, we live on a perfect planet which has somehow managed to avoid sterilization events. Not sure about Olympus Mons being 100 million years old. There are lava flows 100 million years old or younger, and the calderas were resurfaced perhaps 200 million years ago. But this was late activity. The age of the edifice has been derived from flexure modeling on the aureola. That indicates that the bulk of Olympus Mons was build between 2.5 and 3.7 billion years ago.

          • Certainly all of Olympus Mons lava flows are very young, from sometime 100-200 Ma. Because I have crater counted the larger craters and the distribution is relatively random and the density is low. This includes also the plains to the east of Olympus Mons which are covered in flood basalts of the same age, issuing from giant dykes that I think most likely came from Olympus. Olympus Mons instead is covered in lava flows all of which came from the summit, probably there was a continuously overflowing lava lake at its top before the caldera formed.

            It is possible that there was an older edifice before. Which is likely if the estimate from flexure is correct, although I can’t imagine how they did it. One day I will try to crater count the aureola, the terrain is very rugged and only large craters can be recognized, but it would be possible to get an idea of its average age as a whole by looking at the largest craters which can be recognized even in that chaotic terrain.

          • Maybe not entirely, for example about half to 2/3 of the Indian sub continent now resides under Tibet and is still moving North. Such collisions may be more frequent reducing the total continental surface area.

      • Earths plate tectonics is what keeps the planet from boiling over like Venus did. Plate Tectonics relase heat in small friendly eruptions everyday, recycles minerals and CO2 gases in and out keeping the planet habitable.

        Super Earths thats in the habitable zone, haves interiors that are even hotter than Earths with more mass and haves deeper mantles, they maybe experts, ideal for tectonics with stronger mantle mantle convection and thinner litosphere than Earths. Souch large terestrial exoplanets coud be
        ”Superhabitable” and specialy the ones that orbit orange dwarf stars. They may never have snowball episodes or Climate catastrophes.

        Earths sun is growing rapidly in luminosity, and rainfall weathering will increase, CO2 will be scraped away faster than the volcanoes can replace it in the future, leaving the biosphere uninhabitable for complex life in around 700 million years, leaving just microbes

        • I think there is a real possibility super earths self inflict a runaway greenhouse, it might be that it takes many billions of years for their atmospheres to cool off, so the habitable zone for such planets could be further out than it would be for one the size of our own.

          Carbon planets are a no go concerning habitability. Models suggest their outer crust would still be silicate as water rich asteroids and comets exist, water reacting with the carbide crust to make SiO2 and TiO2, along with relative minerals derived from such, and the upper mantle would be turned to diamond. Diamond is obviously extremely rigid and doesnt melt at low pressure, and is the best thermal conductor of any solid. Basically it conducts the intense heat of the lower mantle right to the crust and prevents any possibility of convection. The simple answer is carbon planets are lava planets no matter where they are.

  2. Im intrested in rare igenous rocks, and the superalkaline, sillica undersaturated ones are the rarest, since they form only by small ammounts of melting. The rarest are the foidolites thats most sillica undersaturated and most enriched in Alkaline minerals and elements. Rock collectors dream really, Alnö Igenous Complex haves both Ijolites and Carbonatites showing their both haves a CO2 rich relationship. Souch sillica undersaturated volcanism have become more common in the later part of Earths history

    Here is an Ijolite, thats the plutonic deep coarse grained version of Nyiragongos extrusive Nephelinites. Ijolite is a very uncommon rock, formed by minute ammounts of partial melting, and the extrusive form is even rarer on Earths surface. These groups of rocks makes up much less than 1% of Earths surface rocks.

    • The extrusive form Nephelinite is almost Impossible to find photos on internet on as samples, rare rocks indeed for soure

  3. A tidy little review, Albert, in keeping with your usual and customary style. It causes me to remain of the opinion that that molecular biology and genetics may be far less tasking than the nomenclature, structure and chemical composition of rocks and minerals.

  4. No eruption on 5th of January so far, but the bad weather is back. Already 19 m/s from ESE according to acme.to.

  5. Many thanks Albert for this article on rocks. I have always (well since my teenage years many moons ago) been fascinated by geology. Geography at school in the 1960s literally bored me to tears where all they ever seemed to focus on was the gross domestic product of various countries. However finding my first semi-precious stones in old volcanic areas of Scotland, it’s islands and also in Cornwall really cemented my interest in rocks and also fossils. My first fascination with the way the strata of rocks formed and reformed was triggered by my first boat trip around the cliffs of North Cornwall and the fascinating folding evident there. That of course then progressed onto reading up more about the gelogy of the UK which I found truly fascinating. I have learned far more from books since I left school than I ever learned in formal education.
    This is what finally drew me to my love of all things volcanic and to being in on this site since its first founding.

    • Gross domestic product: Agreed. Was supposed to learn the same. Read about oceans and rivers, mountains and structures instead. Most knowledge after school, completely true. Poor people who stop learning after school.

    • Agreed.

      I was so fortunate that Dad had an old geography book that featured a *lot* of ‘Physical Geography’. Also, when I was very ill at 9~10, teacher lent me his ‘review’ copy of a superbly written and illustrated book on Physical Geography. Landscapes, erosion etc. Post-viral, I barely had strength to turn pages, but it was a feast for the eyes and wits…

      Some years later, I remember the fuss when those mid-Atlantic mag-stripes nailed ‘Plate Tectonics’. All our Geographers went out and got drunk. The Young, to celebrate, the Old to mourn the passing of paradigm…

      FWIW, I’ve only once been able to remember the names of US Great Lakes, and which was which. That late study was fortunate, as proved to be first question on GCSE.

      I remember becoming very, very nervous due repeated returns of an ‘invigilator’ to peer over my shoulder at the map-reading / transect exercise. On my way out, he stopped me at door and asked what I knew of it.
      I blinked, replied that the land-scape’s shape and proportions surely made it North Wales, and probably one of those ‘blind valleys’ near Bala. I was fairly sure we’d turned off there for a picnic en-route to Anglesey after again being stuck at Queensferry Bridge for umpteen hours. (This before modern viaduct relieved that notorious snarl..)
      He mentioned I’d got more from the map in ten (10) minutes than his ‘Sixth Form’ GCE Geography crew had managed from a fortnight camp on site. Clement weather, too…
      Uh, how had I fared at the ‘mock’ ?
      “Heavy emphasis on ‘Human Geography’: I failed out-right…”
      He smiled, nodded…
      I got a ‘1’, trumping my Physics,Chem & Maths, astonishing my ‘Olde Skool’ geography teacher…

      Much later, by sheer serendipity, my beloved wife and I discovered we had, among other factors in common, a shared fascination with ‘Physical Geography’. Hey, is how the world is put together !!

  6. “Geography at school in the 1960s literally bored me to tears where all they ever seemed to focus on was the gross domestic product of various countries.”
    Oh that does remind me of my schooling, too. German coalfields, city populations. When all I wanted was glaciation and volcanics! All that with Kennedy’s Latin Primer….
    Thanks for the reminder!

    Lovely article, Albert. As always, so thorough.

    • and with rapid deployment parents… i often moved which gave me 4 years of
      “Mesopotamia: the cradle of Civilization” and they got that wrong too.

  7. Dolerite is found all over County Durham and Weardale, as far as the Farne Islands. Usually formed from shallow dikes – probably from the North Atlantic Igneous Province. Don’t think there were actually any volcanoes formed that far east, I’m not aware of any south of Edinburgh. Please let me know if there are any!

    • Dolerite is indeed a subvolcanic fine grained plutonic version of Basalt also known as Diabase. Its often melted and spunned into rockwool insulation by modern industry, contains about 50% sillicon for the thoelitic variant

    • I believe that the dolerite you mention is highly likely to be of the Great Whin Dolerite Complex that dates to circa 295 million years ago and lasting for 15 million years. It is contemporary to the Variscan Orogeny that was occurring further south.

      This comment was held for approval. Approved and demon told not to quarantine you again – admin

      • I have personally walked up a few exting volcanoes in the UK. Arthur’s seat in Edinburgh was the first on on a school trip whilst living in Scotland. The next one was Goatfell on the Isle of Arran, Firth of Clyde, then Snowden on a family holiday and finally a trip back up to Scotland when I twice climbed to the summit of Ben Nevis. Once was enough for anyone but I was a glutton for punishment apparently. Definitely enough to turn the calf muscles to jelly for an unfit lady.

    • Andy, never heard of the Farne Islands before. Thanks for the new place.

      By the way, while Albert’s article points to Greenland as having some of the oldest exposed rock on earth, some studies point to the Nuvvuagittuq Greenstone Belt on the northeastern shore of Hudson Bay (that’s in Canada) as being older. Not that this would interest you, since Canada is so boring.

      • The dates for those still need to be confirmed. Perhaps it has? The date of 4.3 billion years puts it very close to the formation of the earth. The alternative date of 3.7 billion years puts it within range of other rocks. More research needed. It is fascinating

      • Yes, Canada is sort of boring. We went up there from Maine after travelling NH and Vermont and Northern Mass and were utterly disappointed with one exception: Quebec. Quebec is as nice as every othe French place. The rest is not America, and we really didn’t know what to do there, didn’t see any specific country charactre and went back to Mass., USA, without losing any time. The difference is that New England has a visible history and beautiful buildings among even more beautiful forests.

        • This highlights, once again, that I sorely lack the verbal skills required to attempt sarcasm.

          For the record, I’m nuts about Canada and agree wholeheartedly that Quebec is charming.

          • Canada is fabulous.
            After all, it has the international Maple Syrup Stockpile. 😉

            It also has some quite intriguing volcanism that is rarely mentioned.
            The only part I do not particularly like about Canada is their border control dudes. I think that there is a secret law in Canada where rude and psychotic people are sentensed to being border control agents at airports. After all, every other Canadian is extremely nice, it is like all non-nice Canadians are filtered out and has congregated at the airports in an official capacity.
            The US TSA is fabulous in comparison, articulate, nice, professional… I am serious here.

  8. What a prelude to ‘one of those volcanoes’. 😁

    Ah, very nice! Thanks Albert.

  9. Thank you Albert. For the first time, you straightened out my thinking on the temperature versus rock type sequence as the triangles kept interfering, in the other charts.

    Quick question:
    The new quakes seem to be occurring east of Geldingadalir, is this tectonic pressure breaking? I don’t believe it is magmatic is it?

    • I think it started with the new dike putting pressure on the Reykjanes fault. This triggered earthquakes in this region. Anything shallow here is likely hydrothermal. But a developing pathway for magma cannot be excluded. At least, I would not know how to exclude it.

  10. BBC reports activity at Nyiragongo

    “One of the most active volcanoes in the world – Mount Nyiragongo in eastern Democratic Republic of Congo – is spewing huge clouds of black smoke and volcanic ash into the sky.

    Photos posted on social media show Mount Nyiragongo’s crater filled with hot lava.

    Social embed from twitter

    ReportReport this social embed, make a complaint
    Social embed from twitter

    ReportReport this social embed, make a complaint
    Geologists from Goma’s Volcano Observatory say it is not yet flowing, but they have noticed an increase in seismic activity.

    The observatory’s director, Celestin Kasereka, told the BBC sporadic explosions were responsible for the smoke and ash that can be seen across the city of Goma. Despite this, Nyiragongo is unlikely to erupt, he said.

    Residents have been advised to stay calm, but this will be difficult for many, as the devastating impact caused by last May’s eruption is still fresh in their minds.

    It led to the deaths of 32 people, and forced thousands from their homes.

    Many fled to neighbouring Rwanda while others are still living in temporary camps in Goma.”

    • Not strange, Nyiragongo is a young and highly active volcano, sounds like really strong intra – crater lava fountains, there is an open conduit there. This is a really peculiar volcano and thats why I writes an article about it. Any Photos yet of the activity?
      It coud be the magma column thats surfaced resulting in vigorous lava fountaining before calmimg into a new open pipe lava lake

      Nyiramuragira the sister volcano have also gone full blown shield building, a remakable productivty for being so very alkaline

    • 268 tons of SO2 released daily now.. from latest data. Its way to go because 2004 it released around
      50 000 tons a day for years! The lava lake emitted less SO2 towards 2010 and onwards. Just before 2021 draining the magma colum emitted around 7000 tons a day, still higher than halemaumau overlook that was 3000 tons a day.

      • Souch intense intra crater activity is seen as a huge steam cumulus column over Nyiragongo

      • Some numbers. That’s great. Hope the people of Goma get them as well and understand them.

  11. “Group I is a rare type, formed from pure mantle material and found only in extreme oceanic crust.” This is why GutnTog was excited to point out the olivine in the lava during his Geldingadalir videos?

    • It proves a mantle source, and a fairly hot one at that. Olivine in Iceland is normally crystals that solidified in the magma chamber and were brought up as small crystals. Getting it in the lava is unusual. Hawai’i can produce significant olivine – that has formed the green beach.

      • Probably in Iceland the magma spends longer in the crust before erupting than what happens in Hawaii, so allows olivine to settle out. Bardarbunga and Grimsvotn have a lot of olivine cumulate underneath them, dense crystal mush. Bardarbunga partly hides this by having a large magma chamber but Grimsvotn, having recently had a major eruption in the 1780s, has still got to recharge and shows a positive gravity anomaly usually only seen in dead volcanoes.

        No idea how long it actually takes for magma to go from the mantle to actually erupting in Hawaii, probably it is quite slow in the deep rifts but the magma flowing as a liquid in the upper conduits moves fast. 2020 eruption of Kilauea erupted lava that was in the deep magma system only a month earlier, with similar numbers for the ongoing eruption. In 1959 it moved up from 50 km depth to the surface in 2 months, and 12 km in 3 days, which is the same sort of distances we are talking for Fagradalsfjall.

  13. Offtopic positive news regarding covid

    I am trippled vaccinated and I had severe covid in March 2020.

    In September I caught covid again and it was very mild (just headaches, sneezes, loss of smell), but still got fatigue lasting 3 weeks. This was 2 months following my second dose.

    In November, my local neighbourhood got a huge covid outbreak, and I had indoors contact with several infected people (a day or two they developed fever and got ill). I did not develop covid. Just a sore threat and that was it. Tested negative.

    Not it’s January (a month after my booster) and I live without fear for covid. After Christmas I had an indoors dinner with a friend that was infected. He tested positive right in front of me (after he heard about his ex-wife falling ill and testing positive). I remained almost assymptomatic. Got a bit of dry cough (and little tiredness) 3 days post-infection but that is now gone, and my tests have been always negative.

    I think I am developing a good immunity to Covid.
    But so far I wasn’t exposed to any sick people with high viral load, sneezing or coughing over me.
    Not willing to test that scenario!

    I should also say that, since I got covid in 2020, I try to keep my health and physical fitness in top shape.

    My experience shows that:
    – you can indeed catch covid repeated times (including 2 months after last time).
    – vaccines are pointless to prevent reinfection, but probably help against severe disease
    – that viral load is an important consideration (avoid someone sneezing on you)
    – that your overall health is also an important consideration (keep yourself in shape!)
    – that immunity probably protected you from moderate illness, for a few months (at least 2)
    – In my own case, fatigue and dry cough are the only symptoms that remain constant (but much milder than first time)

    • I developed a dry cough today. No other symptoms – just the feeling I had in the before-times of “a bit of a cold coming on” – but I had been munching cashew nuts. I haven’t self-tested yet – may do tomorrow if the cough persists.

      • No symptoms the next day, and tested negative. I obviously inhaled a bit of cashew nut.

    • If there is one thing we have learned its that The Dose Really Counts.
      Here we are talking very high exposures from busy crowded rooms and public transport. Masks will have little significant effect. Areas where single air-con rooms are small and busy also (Manaus??).
      The other thing is that we need covids to be constantly circulating to maintain our level of immunity by (in effect) providing regular boosters. There is a very good reason why pre-pandemic, about 4% of Uk colds were caused by covid and about 50% had C19 asymptomatically when first exposed.
      In normal circumstances anti-vaxxers catching diseases and re-exposing us to the wild virus does us all a favour. Here nature, covids and natural selection provide both the disease and the cure, which is neat.

      • Agreed. I might have had it as well after the third shot. I didn’t realize as I was busy with the usual sino-bronchitis I acquire in winter from the radiators’ dry heat. Sneezing and running nose. I realized when family got the same symptoms plus some myalgia (I didn’t have this) and did tests. Nobody suffered including me, the older one.
        Omicron is – that seems sure by now – the new common cold. Letting it go around would help a great deal with natural immunity which is better than the short-lived immunity by vaccinations. A booster though is said to be helpful to get mild symptoms.
        Australians and New Zealanders would do themselves a favour to let Omicron in, otherwise they will live in lockdowns for the next fifty years, just like the North of China, neurotic country, where they are locking people in in Xi’an, and these people say they don’t have enough food and have now been living on noodles for two weeks. I consider this a lot more inhuman than Omicron.
        Omicron could be the way out of the desastre when politicians allow it to happen. So, Boris Johnson has been doing the right thing.

        • I’d like to add that in case I had it I have not the slightest idea where I got it being very careful. The only possibility is the super market or the gas station. So, with Omicron lockdowns are senseless. It is everywhere, exactly like the other four common cold coronaviruses, and one of them is thought to have developped in the pandemia 1889-1891.
          I still have to listen to a supposedly brillant talk a collegue recomended to me by Dr. Peter Attia and colleagues. You’ll find it. If not, tell me, then I will provide the link.

        • Will say as an Australian that Omicron is here, you can look at the case numbers of the last month.

          • There is also every effort being made to avoid further lockdown, no way is it going to happen we shut the borders for 50 years. By mid 2022 I think the pandemic will be over for all purposes, covid will not go away but it will be so ubiquitous there is no point avoiding it nor will you be able to no matter where you go, as you all say just another common cold basically. Was definitely not the case in 2020, but things have changed now.

        • This jumps a bit to conclusions. I had covid myself back in November. It was not mild although I avoided hospital. Without vaccinations I would have been in hospital, I expect. The vaccines do not fully protect against contracting covid, and that protection declines in a couple months. The virus manages to get in. But it does protect against severe disease: the cells manage to fight off the infection. I noticed with the booster that I had the same symptoms as in real covid: headache, fever, etc, which lasted a day or so. Of course that was the immune response, not covid itself which you cannot get from the vaccine. Astrazeneca claims that this protection may last for life. Hard to proof. A previous covid infection should also provide protection, perhaps better than the vaccines, perhaps not. Omicron is now exploding in a world already well exposed to previous variants. It seems to get into the cells, but it does not cause as severe disease. But science is not yet ready to sign up to this conclusion. We do not know what omicron does in older people as so far it has spread mainly in younger people who were also less affected by earlier variants. Johnson may be lucky this time, but it could also still backfire. Not that he had much choice: it was too late to be able to do much. What we see at the moment in the UK is steeply rising hospital admissions and (since a few days) a hint of a rise in the death rate. That is mainly unvaccinated people. It is still possible that omicron is just as bad for them as previous variants were. We all hope but cannot yet be sure. This may be the variant we needed but it may not be. What we do know is that by February it will get better as this wave dies down. At that time the next question will arise. Does omicron cause long covid? Long covid has affected people who had only mild disease: it is not particularly related to the severity of the disease. (There are exceptions: not all long covid is the same and many people who were on ventilators may take a long time to fully recover.) We can’t just assume we will be ok. And a final point: omicron is just another variant. We may get another variant which also re-infects people, but causes more severe disease. The variants are the luck of the draw. This is not yet the common cold. It is more like the flu: there will be waves of different types with different effects. Remember that the Spanish flu got so bad only in its fourth wave, and took decades to finally disappear. And on a cheery note: this was the third corona virus in the past twenty years, and perhaps the least lethal of the three. This is clearly a virus which has gained the ability to jump to humans. There will be a fourth one, and based on the past twenty years, it could happen within a decade. Without making any judgement on how to handle or fudge the epidemic, covid should be taken seriously.

          • Albert,
            Thanks for bringing up the actual status of the knowledge with respect to Omicron, people forget that it is assumed to be less severe compared to Delta, which was bad compared to the original strains. Omicron is assumed to be comparable with the original strains with respect to severity.

            On the long Covid, it is bad, having been diagnosed with Covid in October 2020 I can assure that I wasn’t really ill, could continue to work from home, but the effect on my nerve system was huge: smell recovery took almost a year and I’m still very sensitive to vapors and pollution: I start coughing.

            Virusses are known to mess up our immunity defense: Some can easily prevent it from doing the job (HIV), some can hide in your body for decades (Hepatitis, syphilis, ebola).
            Covid is known to induce auto immunity reactions: where the main damage to the organs is caused by your own immunity system going nuts. This is the main reason mass immunity is not the right approach that will help us: to many persons will remain with damaged organs for the rest of their life.

          • Thing is the alternative to mass immunity is extensive restriction of activities, lockdowns being enforced, weeks of expensive enforced quarantine any time you go more than 10 km from your house… generally just unpleasent to deal with. That is what Australia was doing for 2 years, while the rest of the world burned. Melbourne spent more than half of 2021 under lockdown, the most of any city worldwide. In the end it didnt matter at all, it just delayed the inevitable, it is unfortunate but the only option is to let it go through, and try to prepare the population. Measures to avoid the virus are important but should be left to the individual not the government.

          • I wasn’t commenting on the methods used to control the disease. Different countries did different things. The UK actually did quite poorly by being late to lockdown. This is based on the death toll which now runs at about a third of what was predicted to happen without any action. We knew much less about covid at the time, but remarkably the early models which predicted half a million covid death from an unconstrained epidemic in hindsight were remarkably accurate. Brazil did particularly badly. China did well but now finds itself vulnerable. The biggest problem we have is vaccine hesitancy. People refusing the vaccines are the major cause of remaining lockdowns in Europe. Of course you can just say it is their choice, but the issue is that the unvaccinated were predicted to collapse the health service and that impacts everyone. It has already happened in the UK, caused by nurses and doctors being infected with covid by their patients. Where I live, the waiting time for an ambulance is now over 10 hours – and that is for life-endangering situations. One region requested that anyone suffering a heart attack or similar should take a taxi to the hospital. And the peak hospital pressure is still two weeks away. Should vaccine refuseniks be denied hospital care? That would be inhumane. Different countries, different choices.

          • Coronaviruses mutate rather readily so we are continually exposed to new strains and have been for probably 200MY.
            Ideally the circulating strains should cover the breadth of main possible variants but of course this can never be guaranteed. Even C19 would probably have killed about 1% of the population, mostly elderly and immune compromised, plus some carers, had it been let rip with modest precautions. In a world of 100 years ago, that would have been it.
            Coronaviruses routinely jump species and always have.
            Remember that B-cell (antibody) immunity hits only exposed proteins and is rather specific. T-cells can attack (by killing cells with chopped up virus parts displayed while infected) the core proteins many of which are highly conserved. One reason why infection with the wild virus provides better protection than vaccines (unless killed or partly deactivated) that only use the exposed parts.
            Vets know lots about coronaviruses, some are deadly (killing 80% of piglets for example).

          • It’s been admitted though that in half of the hospital admissions the CV wasn’t the reason for hospitalisation, but an accidental labatory find.
            In this case I am 90% sure that the optimists will win.

          • Hospital admissions have sharply increased in the past weeks. Your statistic would not predict that. Let the data decide.

          • With further lockdowns we can go on for 20 years like that. This is the ideal variant to let it run for the purpose of herd immunity.
            You probably didn’t have it. You were sick before it first appeared in J’burg. Dr. Coetzee, SA, said early on, that she considered it harmless, and serious virologists including Dr. Fauci are getting to the same conclusion.
            Aside from that people always had also Long Influenza which we know by now. Some people, not too many.

            But the worst is the panic mood and fearmongering. Fearmongering is atrocious, and the media like it. Scenarios and films of the Phlegraen Fields going boom, big tsunamis, endless repetitions of 9/11 with people falling from burning towers and making people afraid like a herd of sheep: That’s media stuff, and I call it manipulation. And I call it evil now.

          • In all likelihood I had the delta variant. But I also know of someone (sister of a friend) with omicron who is on a ventilator in hospital. Omicron is not harmless. It may be less severe, but even that is still undecided. I do expect that in a few months time, we will get back to normal and will manage to live with the virus as we do with flu. But we will have waves of covid for some years, and vaccine development will have to continue.

          • Not to mention the recent fancy with a Cumbre Vieja landslide.

          • Farmeroz, oldest people lose their immunity completely. Esp. what the thyme gland has produced in their youth is lost. That’s why we die. When we are ready to die we mostly die of an infectious disease. It can very well be seen in long-term cancer patients esp. when they want to die.

          • Besides, Albert, I can already tell now, that my sort of daughter in law will have “Long Covid” as she is a hypochondriac and also sort of lazy, as she lets my son do most of the shopping and cleaning up. Just saying: There are certainly real cases of Long Covid, but it can also be comfortably used as an excuse, nobody can controll if you really have fatigue (you yourself probably don’t have it) or whether you hide behind it which you wouldn’t do as an upright man.
            But the first thing she did was looking for a scapegoat. That happened to be me as I have been coughing in the morning due to sino-bronchitis, for four weeks. The problem was that my tests were negative and also the tests of my oldest son who had already left and also my test before Christmas. Besides my booster was precisely two and a half weeks old. I was still the scapegoat.
            Albert. I had gone to Mass. Catholic. Very glad about it. It was the first time aside from some deaths I needed mass. The priest didn’t talk about Covid. I will keep his words that were balsam to all in my mind. I am so glad I went to Mass. On foot. I had plenty of time to think about it.
            Natural sciences and mass is no contradiction, doesn’t need to be. We might need mass because of the shallowness of hurtful people.

          • Sorry, Albert, you know we all appreciate you, including me, but I tend to contest this hospital admission stuff:
            Here:
            The inconvenient truth: More patients were in hospital two years ago than during current Covid wave, writes SHAUN WOOLLER
            https://www.dailymail.co.uk/debate/article-10373441/More-patients-hospital-two-years-ago-current-Covid-wave-writes-SHAUN-WOOLLER.html

            This in the main fear-mongering paper.
            The curve of CV-pos. people:

            It is starting to rise at some point in November. Normal Covid hospital admissions used to raise ten to fifteen days later. Not the case.

          • I prefer to get my news from neutral papers. The daily mail certainly is not in that category. The flu epidemic of 2017 was the last great hospital crisis in the UK. Any bed occupation level over 85% is considered dangerous and should not last long. This happened in 2017 and it is also the case now.

            Covid cases in hospital as of yesterday was 40% higher than on Dec 31 (one week!). The NHS writes that the majority of patients with covid in hospital were admitted because of covid. There are cases where covid was discovered after admission but these are the minority. For some of these, the admission was not related to covid but for some it was, e.g. people admitted for stroke are more likely to have covid.

          • By the way, hospital numbers for England (not the UK) can be found on https://coronavirus.data.gov.uk/details/healthcare?areaType=nation&areaName=England These are fairly reliable although some hospitals may not have submitted data on some days, esp. weekends and holidays. They are for covid patients. At the moment these make up around 20% of all patients in hospital. The current peak is not nearly as high as the two previous ones. The previous waves predate vaccinations, and about half of covid patients in hospital are not vaccinated. The good news is the number of patients on ventilators which has not increased in recent weeks. Is that because omicron does not require ventilation, or is it because of the booster program in november and december? We don’t know yet. I hope the former! Of course, each country is different. I don’t have numbers for Germany or France. The Netherlands was at breaking point for the hospitals already a few weeks ago, well before the omicron peak. That may just indicate it has too few hospital beds for its population.

            (Hospitals at the moment are very keen that any non-covid patient really does not have covid, so test extensively before admission. It also keeps admissions down. One place where that is not possible is in maternity. The midwives are especially vulnerable to contracting covid, and that seems to be the section of the hospital with the highest staff absence.)

            To lock down or not to lock down? A brief lock down would have helped to avoid the current crisis in the UK where you’d better not have a heart attack or stroke. But lock-down can not be a long-term solution. I would agree on that. If omicron has made covid manageable, we should bite the bullet at some point and go back to normal life, best done a few weeks after the peak of the epidemic.

          • If journalism was strictly truthful, factual and accurate, absent opinionation, coloration, obfuscation, and comic relief, then audiences would turn elsewhere for their ‘nooze’ along with the sponsors who rely on the media within which to peddle their wares to the braindead proletariat.

          • and everyone would accuse them of bias.. I don’t actually mind reading opinions I do not agree with, as long as they are making a real case. It is healthy to read both sides. It should not be based on selective data though.

          • Denali,
            The loss of immune response due age is of course true.
            However some people have a compromised immune response in their 50’s, and others are hale and hearty into their 100’s (several centegenarians caught and recovered full form covid in the first wave).
            That’s why it still pays to vaccinate the old.
            PS There is no doubt that admissions are rising, unsurprising given the case numbers. However I suspect that, whilst being a bit cautious, most of the population now being vaccinated are asking themselves “if not freedom now, then when?”

          • Farmeroz,

            If COVID hit in a time before modern medicine, it would’ve likely had a considerably higher IFR.

            I think people forget how many lives were saved in this pandemic by supplemental oxygen and the full repertoire of lifesaving medicine (especially Dexamethasone; steroids).

            Remove all of that and tell me the death rate isn’t way higher.

            Albert: As always, you take a thoughtful, considered approach. I appreciate your positions because you remove yourself from emotional / ideological inertia of people who already formed their opinions about COVID and will not have their minds changed by data or the experiences of people actually dealing with it on the frontlines.

            With respect, I think people have a tendency to forget that they’re not the ones dealing with the actual reality of COVID, and it’s very easy to have an opinion that we should all just toughen up and suck it up with zero stakes in the game (that is unless you need medical attention…).

          • Let us truly hope Omicron is as mild, in reality, as it is in the minds’ of people who already formed that conclusion.

    • Harmonic tremor readings have climbed also and no quakes since 18:00 last night.

      • Big storm in Iceland. Data from seismometers is useless due to wind noise.

        • Yes, and this morning thay have added 4 quakes that werent showing on the list at 4:00am. Maybe they are short-staffed.

        • 31 m/s now, never seen such a value.
          So… still waiting =)

        • If I check the webcams and meteo pages, I don’t see that high wind, nor bad weather.

          There is some wind (14 to 18 m/sec) in the area, not sufficient to explain the high tremor readings.

  15. Interesting piece with a systematic in rocks that is useful, many thanks.
    It will go on and should.
    The Wyoming Craton seems to be of similar age (Gneiss), probably also the Siberian Craton?
    Two thirds covered by water seems a bit too relaxed as an estimation as 72% is covered by water, not 66%. So it is closer to three quarters and has been much more in the Cretacious.
    A varying sea level (very low at the end of the Perm, very high in the Cretacious) seems to be nature and not man made.
    The sea level is often measured in a completely volcanic structure, the Pacific including the Indian Ocean. This seems silly to me as volcanism permanently changes the landscape, and there is also a good deal of erosion on islands.
    The real human mistake was therefore (in my eyes) to build mega-cities too close to the ocean, but nobody knew anything about Earth’s development at the time.
    The elites who made those mistakes tend to forget self-reflection. Instead they push it on every human being (that evil sinner) and his way of life. If Miami didn’t exist and NYC were further up in NYS nobody would talk about it. The New York Focus can nicely be seen in senseless discussions about a land slide on La Palma. New York which would have a little wave of two metres or so is notoriously the centre of pieces whereas the Canaries who would have the real damage are somewhere in the backyard.

  17. I have a bit of a problem with granites.
    Given their location they must have solidified very very slowly indeed (hundreds of years or more), yet their crystal size is typical in the ten mm range. Generally its quite easy to get crystals of this size with a few days of cooling (or less) in a lab.
    Now its true that there will be many nucleation points, but slow growth should allow large crystals to grow at the expense of small ones (its a surface energy effect).
    Further I find it hard to believe that all these crystals formed at the same time, presumably one (probably silica) crystallised out first to a bunch of crystals with included melt that formed later crystal but why so small the first crystallisation?
    So what is the procedure in detail?

    • Better call it Gneiss, also mentioned under the picture of Pigg’s Peak in Swaziland (second last).
      “Gneiss is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks.”
      Further down the term granite gneisses is used.
      https://en.wikipedia.org/wiki/Gneiss

      • How do you get a magma that is only SiO2 out of felsic magma though, would need to have a temperature of 1700 C to be liquid, which is more than twice as hot as most such magmas erupt. Not even sure any volcano is capable of providing that temperature, maybe the deep plumbing of Hawaii and Iceland but even that is really pushing it, also no felsic rocks there either…

        Maybe not a novice but im also not a geologist so maybe this is actually true, but it would seem there is some weird stuff going on to leave SiO2 as a melt at a temperature not even half of its melting point. Maybe there is extreme volatile content giving it a hand.

        • Yes, the volatiles get concentrated along with the SiO2.

          • What Anthony said. 🙂

            May be way oversimplified, but you can think of a granitic melt as a complex chemical mixture. As seen in Bowen’s reaction series in Albert’s article, certain minerals will start to crystallize out at (relatively) higher temps first. this will also deplete the remaining melt in the elements (Mg, Fe, etc.) that crystallized out first and enrich the melt in other elements K, Al, etc.) and volitiles.. This whole time, silica in the melt is combining with the crystallizing minerals to form the silicate minerals. if the melt is oversaturated in silica, quartz will crystallize out int the interstices of the body after the rest has crystallized.

        • Yes, this is my problem. SiO2 is very refractory, which is why quartz is used for very high temperature equipment. I would be quite surprised if it had a lower melting point than post of the other constituents otherwise lava would not readily form under 1700C, whilst in fact we know they exist circa 1000C.
          TBH I am quite surprised there is no standard answer that everyone knows, has been tested and trots out as gospel.

      • Which is really strange since its a mineral that haves a very high melting point. Pure sillicon dioxide glass is very hard to melt and to work with. Sillicon Dioxide refactory bricks lines many blast furnaces

        Sio2 in a Ryholite magma is just a part of a melt solution that haves a much lower molten temperatures, and it freezes out as pure sillicon dioxide crystals when the magma cools

        Magma melting and crystalization process and physics are Indeed very complicated. Infact all elements in the universe can form crystals and melts and vapours, just depends on temperatures, a behaviour that goes far beyond the sillicate minerals

        • Think honey. Even though the melting temperature is around 45C, the freezing temperature is something like -50C. In between it is sticky, partial melt.

          • Partial melt is what we are talking about. Its the stuff crystallising out in grains within the melt, and most of these will have relatively precise melting points simply because they self-purify by crystallising. The bulk is actually a mix of solid crystals and liquid melt, more like concrete than slurry in concept.

        • Rocks does not have a distinct liquidus melting point, they are made of minerals with difficrent melting points, and they become gradualy more molten at increasing temperatures. Perhaps these granite magmas at advanced crystalization at around 700 C coud be tought as ”wet sand” in nature. Astenosphere is also kind of little like wet sand or densely densely packed snow in thaw weather condition

          At over 1250 C most – if not all magmas thats not Komatites, are a full glass liquid. Nyiragongos 2003 lavas from the lake was only glass and no crystals at all..

          • I am talking NOT about bulk lava (actually magma in plutons) but the individual sequence of crystallisation and each component will have quite a precise melting point.

          • I don’t have the stock answer! But the melting temperature and crystallization temperature are very different for quartz. The latter is very low, around 600C or so. The former is about 1700C. That is why I compare it to honey which also has that large difference. In honey, if you start with a solid (deeply frozen) and heat it, it stays frozen until you hit +45C where it melts and becomes effectively sugary water. (Microwave will do that very fast.) But start with a melt and slowly cool it, and it remains a liquid until very low temperatures. You get crystals forming (melt fraction reduces) which make it much more viscous, but it is not a solid. (Although over longer time it will become one.) The sugar remains supersaturated in the water. That is how I envisage granite. Right or wrong.

        • Water behaves alot too like minerals and is technicaly a mineral solution. It can form crystals, it can form rock known as Ice. It can also find its way into sillicate minerals

          All elements.. in the universe probaly can display crystal formation and mineralization and melting and freezing

          But its the ( stuff ) minerals that are acossiated with Sio2 bonds that We usualy call
          ”minerals”

    • Admittedly I don’t know the answer to this! It might be because the melt fraction in granite is not very high and it is not to ‘runny’. The size of the crystals must also depend on how mobile the material is inside the magma. Perhaps a real geologist can tell us!

    • Finally a closer look at a couple of my favourites.

      Basaltic porphyry
      https://i.imgur.com/RofqmM2.jpeg

      The other side of the big pink granite
      https://i.imgur.com/qOTVfT3.jpeg

      And a chonk of massive quartzy stuff
      https://i.imgur.com/K221L3R.jpeg

      NOTE: Its really difficult to get a good photo of a rock! I put my rocks under water so you can see the colours without too much specular reflection. The light wasn’t really bright enough so the f-stop was rather low and I am also blind in one eye, I had difficulty getting enough of the surfaces in focus to really appreciate the crystals.
      For anyone interested I used a Pentax K-M with a 50mm macro lens.

      • Hi Nell, are those collected from the beaches on the west coast of Scotland. Just asking because they look very similar to many I have collected from beaches there. Thanks for sharing your collection.
        I have one lovely rock of pink granite split by a smooth greenish material, that I am fairly sure is lava, that I picked up from a beach on the west coast.

        • There are some fantastic rock formations in western scotland. I remember finding a vein of brecciated jasper a good 3cm wide in rock on a beach on one of the islands. I still treasure the piece I collected.

    • Nope to all those places! I live on the east sussex coast. Most of the beaches here are flint but I am on a river estuary next to a bay which seems to catch some drift from further west. Otherwise I have no idea how these rocks got here, they are certainly more similar to the rocks I used to find up on Dartmoor.

      • Hi Nell. One possibility is that those rocks come from ships ballast. At least that is the explanation my husband has used for some of the clearly non-local stones I have found on the west Sussex coast where I live. Another possibility is that they come from the Cornwall area attatched to the roots of kelp and swept along by the longshore drif which on the South Coast is west to east. I admit to being amazed at the great variety of the rocks you have found on an east Sussex Beach, lucky you!. Most of the rocks I have are from Cornwall, Western Scotland and Islands, and Wales, all areas where it is not at all unusual to find such stones. If you ever visit Cornwall try to get a chance to look at the old spoil heaps from the old tin mines. I have found tourmaline and amethyst amount the rocks there. Otherwise my semiprecious stones are Agate from the Isle of Arran and garnets from the Isle of Mull plus many really interesting banded stones from the west Scotland beaches. Ah I miss those days in the 70’s when my brother and I drove my old Morris 1000 around Scotland for 2 weeks. He thought I was mad carting a good few pounds of interesting stones home in the boot of the car. My rock tumbler worked overtime for a few weeks as I polished the best specimens. My biggest regret is not labeling them as to where I found them. Even though I am over 70 now I would so love to revisit those places. My most unusual mineral was green talc that was a band on a large slab of coal from the open fire we used to have in the 60’s.

        • Hi Alicia,
          ships ballast is a possibility, I did a quick bit of research and it seems that water is now used as ballast and has been for about a centuary. The pictures I looked at of old rock ballast the rock wasn’t good quality, certainly nothing good enough to build with. I think longshore drift is a more likely explanation, the east side of the pier here collects a lot of back wash from the wave direction. Its the only reason I can think why there would be such a variety.
          In the late 90’s I cycled from St. Austell in Cornwall to Sidmouth in Devon with some friends and I spent a very pleasant couple of hours fossicking around a spoil heap. Came away with a bag full of tiny quartz points and a bit of amethyst. My friends thought I was mad! Would love to do a proper rock hunting trip there, some amazing minerals in cornwall. The yorkshire dales are also a great place for unusual minerals, a trip down the blue john mine in Castleton is a must for rock lovers.

          • Thanks for the info on the ballast Nell. good to have updated info even if I a century behind! 🙂 Water makes much more sense.

        • Alicia, did you ever visit the Gem Rock Museum in Creetown on the Dumfries Peninsula?
          I hope you did. It’s an amazing ‘gem’ of a place tucked away in the countryside and I can wholeheartedly recommend a visit to it. Fabulous displays and information, a workshop, and goodies to buy. I’ve been there a few times on visits to the area.
          https://www.gemrock.net/

          • Sadly Clive I have never been there. It sounds amazing and if I can ever convince my son that we should go on a tour of the west coast of Scotland I am certainly going to keep a note of that link. As I am already into my 70’s I would need to talk someone into driving up there with me. Too far from the South Coast for me to manage on my own But I am working on my son to visit the Isle of Arran with me. I know he would love it as he loves the countryside and is an avid wildlife photographer as well as birdwatcher. So maybe in a years of so I can persuade him. I so want to get back to some more interesting beaches than the mainly flint stones on my local one.

        • The former. Cuckmere is a short bus ride away, but the beach there isn’t as fun as mine. The proximity of the cliffs means that flint predominates and there isn’t a bay to catch the backwash. The estuary and cliffs though are very popular, a lovely walk with some nice wildlife all year round.

  19. Thanks Albert for the dictionary!
    Gonna file this one away for further (and frequent) use.

    Also, noting a 930mb low has bombed about 500km WSW of Iceland.
    Pressure this low is capable of winds equivalent to a CAT3 hurricane…and would be no surprise if land-based seismometers are getting impacted. Not sure if Iceland is getting the strongest winds though, as it is on the NE/wraparound flank of the low, plus the low is still a ways away.
    It’s amazing to think how far the low-frequency sound waves created by waves smashing onto the coastline can be picked up by seismometers.
    For instance, during hurricane/TS Sandy, seismometers in California picked up the wave action going on nearly 3,000 miles away.

  20. A haze has descended upon all the webcams, and it’ll be dark soon. Looks like bad weather too. So unless the hot stuff comes out tonight (personally think it will be tomorrow or at the weekend if it does) we’re not going to see anything.

    As regards above – I don’t know if i’ve ever had Covid as I’ve never tested positive for it. Having said that I usually get 5/6 bad flu-like illnesses/fevers a year on top of regularly weekly colds, so it could have been any one of those. Surely by now I have some level of natural immunity, I’ve got to have had the original, Delta etc., I’ve been shopping and working away from home since the beginning. Testing weekly (now bi-weekly) since at least February this year and some of last year. I did an antibody test in November and they said I didn’t have any antibodies. So god knows.

  21. Thanks for the article, Albert.
    As usual, you caused me to wander off, looking at related stuff. I found this map:

  22. Albert,
    “The good news is the number of patients on ventilators which has not increased in recent weeks”: That’s right and is the most important fact. That’s why Germany will prepare normal stations for that and tell the doctors to not do operations that can wait, for a while. Operations that can wait are joints, back operations, a number of surely benign tumours, Plastic Surgery and also some stents and so on. This is different from the UK. As soon as this is finished people can have their operation date back, whereas in the UK they often have to wait for a long time. The most important fact is no ventilation which means less dying.
    Concerning 2017/18 we had the same problem, but somehow managed. The main problem is that hospital beds are reduced for economic reasons. I think this has to stop, and the profession of nursing needs high recognition, better working hours and a salary with which people can live. Instead, senseless procedures belong under the magnifying glass and checked.

    • In South Africa we have lifted virtually all restrictions, except mask wearing in public places, and our covid numbers are dropping continuously, both infections/hospitalizations and deaths. It would seem Africans are blessed with fairly robust systems.

  23. The emplacement of Granites and huge batholiths have always been problematic, knowing that some of these huge Igenous complexes solidify only 10 to 30 kilometers underground in the upper brittle continetal crust. How these huge batholiths make room for themselves are mysterious.

    In the lower ductile crust its No problem as the country rock is quite hot and ductile, then the hotter granite magma can convect, and rise because of its lower density without breaking the country rock. The enviroment around is
    a hot solid But over thousands of years its behave like a liquid. In the warm, ductile lower crust where rocks are easily deformed and the solid country rock can be thermaly pushed aside by the rising Ryholite- Granite pluton.

    In the upper crust the rising warm magma runns into problems, it haves to expend energy to warm the country rock, But rock is a poor conductor of heat, and Once the enviroment is heated it becomes ductile as well, still breaking ”stoping” and intrusions are common along large plutons as they cut into the country rock and heats it up as well. Granite magmas have a density of 2.4 Mg/m3, much less than most other rocks and that gives them tremendous buoyancy. Very big diapirs of granite may simply heat the local upper crust around it to ductile temperatures.

    Souch large sillecous magma Bodies can feed large continetal caldera systems like Altiplano Puna region

      • And I’m given to understand that it was glaciation in part which cut that Valley and created Half Dome.

    • Granite and Ryholite and Ryholite-Pumice have the same composition, just way diffrent cooling rates and therefore crystal sizes.

      Coarse grained granites are difficult to melt perhaps because the Sio2 have cystalized out as pure sillicon dioxide Quartz crystals. They are nearly Impossible to melt without plasma torch.

      The pumice is just glass and was able to melt that in our fireplace with the strong hurricane suction of air under the ash bin. The melted surface became black obsidian. There the Sio2 quartz had not come out of the mineral melt solution

    • I expect it happens very slowly, a few cubic meters a day intruding from below, every day for a million years or more. The overlying rock gets pushed aside very slowly, and above the ductile/brittle transition, with the occasional quake. Some would also melt and be assimilated into the magma, growing the chamber that way.

  24. We just had a harsh storm with some quite violent waves here in the Faroes, a fair bit of damage to some buildings and some cars got wrecked in one village. But the worst I’d say is the damage to an exposed dike in the village of Gjógv, a huge chunk has been torn out off it and the rest has become loose and is quite ikely to go in the next storm, which doesn’t have to be as violent as this one.

    Some video footage of it here https://kvf.fo/netvarp/sv/2022/01/06/20220106nettrappugrodgjogvok?

    • I kept thinking “oh I remember that, oh I remember that, oh I remember that.” In a mere twelve minutes, six months of the year flashed in front of my eyes. Thanks for the link.

    • Reunion eruptions are absoutley tiny compared to the Galapagos eruptions
      But Galapagos is way more powerful as a mantle plume and much more melting

    • The start of eruptions in the Galapagos is always something to behold, even the small eruptions are crazy intense, much more so than eruptions in Iceland or Hawaii. Probably it is not anything out of the ordinary but this looks pretty serious, at least of comparable scale to the eruption in 2015. I assume it is also in the same place too.

      Would not have expected Wolf to be the next eruption there though, going statistically and also based on recent data I would have picked Fernandina.

      • Might not be quite that big, the Galapagos volcanoes tend to do relatively small eruptions on land, short lived low volume but high intensity, except Fernandina which has also got lots of tube fed pahoehoe (no lava shields though). Big eruptions tend to happen in the deep sea, out of sight, Wolf is no exception.

        Sierra Negra is a major exception though… It is really in a whole different league to almost any other volcano on land outside Iceland, except probably Mauna Loa. 1979 eruption was 1 km3 of lava, in 2 months, and this was a summit eruption from a ring fault. Actual flank eruptions can be multiple km3 in volume and seem to be extremely fast, like flood basalt intensity fast… one had fountains just short of 1 km high. Last of these was only a few centuries ago.
        Fernandina is the Grimsvotn of the group, frequent small eruptions and sometimes something bigger. Sierra Negra is the Bardarbunga, it erupts less often but it means business when it does. 2005 was the same volume as Fagradalshraun erupted in a week and that was a small eruption. Still waiting on something for 2018 but I think it was pretty big, much more than 2005.

        • Yeah, and that is apparent in Sierra Negra’s shear size. It isn’t the tallest of the Galapagos shield volcanos, but it is by far the largest in terms of square kms above sea level. Isabella island has 6 shield volcanos, yet 40% of the island’s ~4,600 km^2 is Sierra Negra’s shield.

          • To be fair all of the other 3 that are active recently are sitting above the deep sea, like in Hawaii, while Sierra Negra is sat within the bulk of the archipelago and a lot of shallow sea. Darwin and Alcedo are also like this. Curiously all of these also have shallow calderas, while Wolf, Cerro Azul and Fernandina all have deep calderas. I think for the latter 3 their caldera formation eruptions take place down on the deep submarine slopes, while Darwin and Sierra Negra do their big eruptions on land but perhaps cant totally drain.

            There is though something a bit different about Sierra Negra compared to the others, it doesnt seem to do circumferential fissures or caldera eruptions very often. Eruptions like to broadly align with the caldera rim but actual fissure orientation is pretty chaotic, as though the subsurface is completely shattered and lava just leaks out of every crack…

        • Wolf erupted just after I wrote a post about it. I am now worried about Tarawera and Victoria Island

    • But the opening hour of Sierra Negra 2005 was even more Intense I think, it made some amazing lavafalls from the caldera slope of chico

    • I hope the Pink Iguanas are safe.

      Bad bad Wolf is trying to eat those yummy Pink Iguanas again. 🙁

      For those who have not had a Pink Iguana… you have really missed something, they are absolutely scrumptious.

      What? No, it is a drink you silly toad. 😉

      • And you perfer to have giant pythons as pets.. 🤣 Carls next husdjur ( pet ) will be a Titanoboa will be the ultimate firehose to your collection. What happened to the other firehoses? väs, jässica and the other snakes? Did you ate them after a few years? Wants a new? : D

        BTW I love pythons too .. they are soo trusting and cute 🙂

        Pink Iguanas are not sold or breed as pets, its an isolated super – rare Galapagos species 🙂

        • Really cute?
          https://www.bbc.com/news/world-asia-39427458

          Now Indonesians tend to be smaller on an average than Vikings. Concerning iguanas of another kind, the alligators of the Everglades, the imported python (somebody must have left his pets there one day) which loves the terrain and spreads to no end kills so many of them that Florida has long started to chase them.

          • Yes! Do come to Florida for the annual Everglades hunt and to keep the iguanas out of my wife’s precious garden.

      • My oldest son wanted to have an iguana as a pet once. We then read that they can become quite old, 100 years or so, and that they tend to miss their people when on vacation. They can just stop eating and die, feeling desolate and lonely. So we talked him out of the idea and got a cat instead.
        My younger son wanted a Royal Python (smaller snake). We weren’t very happy and said that pythons are only content when they are fed living mice. He changed his mind for a dog, thank God.
        I myself, infested by Enid Blyton’s adventure series, wanted a parrot. My father talked me out of it and I also got a dog.

  33. Frettir from IMO, google translated:

    “Updated 7.1. at 15:06

    The earthquake that began on December 21 at Fagradalsfjall has now ended. Deformation has not occurred since December 28, according to measurements from GPS stations and InSAR images. It is therefore estimated that this abdomen is probably over and it is unlikely that an eruption will begin at this time. Due to this, the Meteorological Office has changed the flight color code to yellow. The Meteorological Office will continue to monitor the area closely and any possible changes that may occur.”

    Over and out.
    For now. 😏

    • “…that this abdomen is probably over…”
      So Fragadalir has had an upset stomach? That explains all the stomach rumbling!

  34. Between Christmas and New Year, I went on holiday to Dartmoor in South Devonshire, I love the place. I find it to be a very spiritual place.

    Dartmoor is famous for its granite tors, I found out that Dartmoor is effectively a lava field from an eruption 300million years ago. Even though the weathering is obvious, you can still see the shape and layering of the lava.

    https://flic.kr/p/2mVSTog
    https://flic.kr/p/2mW2w9h

    • I didn’t know they were so old.
      Another old jewel there, albeit not in a geological sense old, is Wistman’s wood:
      https://en.wikipedia.org/wiki/Wistman%27s_Wood

      All of Dartmoor has once been a forest. Then the mining began and led to the Dartmoor we see today. It’s in facht very unique and beautiful and a heaven for the animals there.
      A painting of Yes Tor by Frederick John Widgery:

    • It’s an early painting. The painter himself was sort of a volcano and here 33 years old. The mythical stuff fascinated him at the time. There was a very sober school of painting in Venice with monumental portrauts and holy scenes of great beauty and colours done by Giovanni Bellini and Titian in the fifteenth century. The greatest collection of Titian today is in the National Gallery in London (16 I think). Then Jacopo Robusti (Tintoretto) and Paolo Caliari (Veronese) seem to have exploded.

    • Thankfully this is a family friendly site. The potential for inappropriate comments aroused by Vulcan’s premature arrival is glaringly obvious.

  37. Thank you Albert for your educating post once more!
    And thank you even more for the link about “lava rocks!”.
    Even though I didn’t get the introduction right away, after searching for that Shakespeare poem it made a lot more sense^^
    How about extending the “Volcanology Basics” with (some of) those absolutely basics articles?
    So one had them always handy if difficult situations are going on in the volcanic world =)

Comments are closed.