Lake Tanganyika: a celebration of water, fish, and distant volcanoes

Fisherman_on_Lake_Tanganyika

17 per cent of the world’s fresh water is found in a single lake. It is the second largest lake in the world (after Baikal), Africa’s deepest lake at 1.5 kilometer, and it has a shoreline almost 2000 km long. Lake Tanganyika is shared by four countries: Burundi, the Democratic Republic of Congo (DRC), Tanzania and Zambia. It is not on the tourist track and not nearly as popular as Lake Malawi or Victoria. Its tropical fish are not quite as psychedelically colourful as those of Lake Malawi, but are even more characterful and more desirable, difficult to keep – and expensive, as I found out starting to set up a Tanganyikan biotope aquarium! Recreating its water takes effort: the pH is 8.5-9, and the water is extremely hard (GH of 15), mainly with dissolved sodium, magnesium, and potassium. It could be called liquid rock if you could find rock with this composition. Luckily for fish keepers its cichlids can thrive under less extreme conditions.

source: fish-etc.com

source: fish-etc.com

Most of the fish species in the lake are cichlids, a family that first evolved in ancient Gondwana, and are still mainly found in the southern hemisphere (geology has a long memory!). There are over 3000 species of cichlids in the world, and over 1500 of these are found in the lakes Victoria, Malawi and Tanganyika. Tanganyika has fewer cichlid species (250) than the other two lakes (700 each) but they come from a much larger number of different groups. It is therefore older, and more closely connected to the evolution of the species. Tanganyika also has modern (living) stromatolites, a large number of endemic crabs, and even a tiny freshwater jellyfish, the only one in all of Africa. It is an amazing place, and possibly the oldest lake in the world. But its water hasn’t always been as extreme as it is now. Its current state is due to a distant volcano.

Africa’s Rift Valley

The East African Rift, which contains Lake Tanganyika, is one of the geological wonders of the world. The Rift is typically 50 km wide, 1 km deep (but as much as 2.5 km in some places), and extends from Mozambique to Ethiopia; it crosses the region where humans first evolved. Africa has been prone to rifting. One such rift caused India and Madagascar to break away from Africa. The scars are still seen in the shape of Africa’s coast line. Another rift split off the Arabian peninsula. The current rift tries to break down this ancient continent even more by forcing Somalia into the Indian ocean. Whether this will happen remains to be seen. Many developing rifts eventually fail, and this one may too.

source: J. Moore, 1898, Nature

source: J. Moore, 1898, Nature

 

Around Tanzania the Rift splits into two parallel rifts, 600 km apart. The eastern one has most of the volcanoes, and the western one (called the Albertine rift) has the lakes. Both rifts started forming at about same time, 25 million years ago. At that time there was a large lake in central Africa (Lake Congo, which disappeared long ago), and rivers flowed into it from the south. The developing western rift captured one or more of these rivers. For a long time it stayed a swampy river valley, but by 10 million years ago two deep lakes had begun to form where crustal blocks had sunk. These became the core of Lake Tanganyika. At times they held separate lakes but over the past 100,000 years the water level has been much higher and it has been a single lake. In places, the sediment is kilometers thick. If the Loch Ness monster had lived in Lake Tanganyika, proven its non-existence would have been nigh impossible! In the absence of such monsters, Tanganyika, as the first of the rift lakes, probably inherited a fish population from the lost Lake Congo.

After the discovery in 1883 of the jellyfish, Moore (Nature, published in 1898) recounted the story of a Dutch farmer, who, on the sudden appearance of herrings in the ditches on his property, sold it, on account of the indisputable evidence which such fish afforded, of the leaky condition of the dykes. He considered that the jellyfish, the crabs and the molluscs pointed at the lake being a relic of an ancient ocean. That is no longer believed: instead, they are now considered as due to parallel evolution.

source: Hydrology and hydraulic modeling of Lake Tanganyika. Otieno Odongo 2013

source: Hydrology and hydraulic modeling of Lake Tanganyika. Otieno Odongo 2013

The water of Lake Tanganyika

Lake Tanganyika has a very poor through-flow. This enormous lake has only three main contributories: the Malagarasi river, the Lufubu river, and the Ruzizi river. The only major outflow, the Lukuga river, act as an overflow: its entrance is over a high rock sill. (In order to control the fluctuating levels of the lake, which caused difficulties for harbours, a masonry dyke about 2 meters high was constructed in 1952 at the outlet of the Lukuga River.) It has the second largest volume of anoxic water in the world, after the Black Sea. The volume is 18,900 cubic kilometres. The in-flow is normally some 16 km3 per year, and rain over the lake adds another 29 km 3 each year. The outflow in normal times is 3 to 4 km3 per year, dwarfed by evaporation at 44 km3 per year. A molecule of water will stay in the lake on average for 440 years before escaping, and 80 per cent of its water will leave through evaporation. Dissolved minerals do not evaporate and have to wait on average 7700 years before finding the single outlet! Lake Tanganyika jealously holds on to what it receives.

The main river in the rift, the Ruzizi, flows into Tanganyika from the north. That is the opposite direction to that 10 million years ago. Over time, geology can reverse rivers. The divide between rivers flowing north and those flowing south is not far from Tanganyika. At the northern end of the Albertine rift, Lake Albert and Lake Edward’s water are both part of the flow system of the Nile, towards the north. Tanganyika belongs (for what little water flows out) to the Congo. In between, Lake Kivu on the border between the DRC and Rwanda, drains to the south. It is the highest of the western rift lakes and the source of the Ruzizi river. The watershed is in the Virunga mountains, a range of highly active volcanoes immediately north of Kivu.

Goma

Lake Kivu and the Virunga volcanoes

The secret to Lake Tanganyika’s peculiar chemistry lies in Lake Kivu and its adjacent volcanoes. The Virunga volcanic field has 18 volcanoes, two of which are active. Mount Nyiragongo is one of the 16 Decadal Volcanoes and at times hosts the largest lava lake in the world. Mount Nyamulagira erupts even more frequently. Both have lava with very low viscosity which can travel for 10’s of kilometers, and the lava regularly reaches the lake. Lake Kivu is suffused with their volcanic produce. Below 250 meter depth, it is saturated with CO2 and methane. (The pH changes from 9.2 at the surface to less than 6 at 200 meters!) The estimated amount of CO2 is a staggering 200 km3. It would be a major hazard if the lake were to overturn as happened in Nyos in 1986, but that is a different story.

The CO2 likely comes from hydrothermal vents under the lake, some 200 meters below the surface, which have been active since 5,000 years ago. The methane may be of biological origin. The water which vents into the lake is rain water, which has percolated through layers of old lava from the Virunga volcanoes, dissolving its minerals on the way.

The vents bring ten times as much calcium into the lake as comes from in-flowing streams. Sodium is also strongly enriched (1/10th of the salinity of sea water), and magnesium (at 0.8 gram per kilogram of water) is twice as high as calcium. (As an aside, this may not be too dissimilar to the conditions on the young Earth where life first originated – but that also belongs in a different story.) Much of the calcium precipitates but some reaches the Ruzizi river. Sodium and magnesium do not precipitate easily and through the Ruzizi, end up in Lake Tanganyika.

Nyiragong and Lake Kivu (source: wikipedia)

Nyiragong and Lake Kivu (source: wikipedia)

Nyiragong and Lake Kivu (source: wikipedia)

The high abundance of magnesium (Nyiranongo has particularly magnesium-rich lava) is characteristics of mafic magma. The term is derived from the MA from magnesium and the FIC from the Latin word for iron. Mafic magmas are also relatively rich in calcium and sodium. Mafic magma is young, and tends to come from the upper mantle. The presence in the spreading centre of the African Rift Valley is not a suprise.

Rivers of change

The final piece of the puzzle is also volcanic. Although Lake Kivu is about 2 million years old, the jump across the watershed is much more recent. About 10,000 years ago, one or more eruptions from the Virunga volcanoes blocked its northward exit towards Lake Edward. These must have been impressive eruptions – one ash layer in the lake sediment is 2 meters thick. Lake Kivu rose by 400 meters, until it found a new exit southward, creating the Ruzizi river. Through the Ruzizi, Lake Tanganyika’s water suffered volcanic pollution.

The damming has been dated from sediment as between 9,000 and 14,000 years ago. The rise leading to overflow into the Ruzizi happened 8,000 to 10,000 years ago. Sediments show that the water in Tanganyika became harder around 4,000 years ago. Calcium deposition began about 2400 years ago. Thus, its peculiar chemistry seems remarkably recent.

The secret of the lake

Lake Tanganyika is an important part of the evolution of Africa. It was at the origin of the rich cichlid species across Africa, through a geological inheritance, and may have seeded the other, younger rift lakes as well as the Congo river. But the water properties have changed dramatically over the past few thousand years, caused by a volcanic field 200 km north, which changed the course of a river and polluted it with elements from the mantle. Fish species can adapt and evolve quickly. But perhaps it is not a surprise that Tanganyika cichlids can prosper in water less extreme than that of their current habitat. I won’t have to put a volcano in that Lake Tanganyika biotope aquarium.

Albert


International Journal of Evolutionary Biology Volume 2012 (2012), Article ID 574851, 20 pages http://dx.doi.org/10.1155/2012/574851 Review Article The Impact of the Geologic History and Paleoclimate on the Diversification of East African Cichlids

Patrick D. Danley, Martin Husemann, Baoqing Ding, Lyndsay M. DiPietro, Emily J. Beverly, and Daniel J. PeppeGeomorphology Volume 221, 15 September 2014, Pages 274-285 156727|| Lake-level rise in the late Pleistocene and active subaquatic volcanism since the Holocene in Lake Kivu, East African Rift

191 thoughts on “Lake Tanganyika: a celebration of water, fish, and distant volcanoes

  1. a great post, Africa is a mysterious continent, like your reference to the cichlids, I used to breed them many moons ago.

  2. Thanks for the great article, Albert. Have you ever written, or thought of writing, a book? I’d buy it.

  3. If you have done Google Earth to death, try Pluto. NASA has released a high resolution map of half the planet (the other half was in darkness). Don’t download unless you have unlimited internet and unlimited storage (and remove the ‘x’ from the start which is there to avoid you accidentally bankrupting yourself). The thing is 70.8MB on my computer.

    xwww.nasa.gov/sites/default/files/thumbnails/image/crop_p_color2_enhanced_release.png

    I think most of what is seen is caused by migrating icecaps. Pluto is just coming out of its brief summer (which lasted 10-20 years) when the nitrogen glaciers evaporated. They are now refreezing, but in different places than where they evaporated as the sun is illuminating different areas of the planet than it did before the summer’. ‘Summer’ should be taken with a grain of salt (ice), as the temperature hovered around -230 C. Which is about the freezing point of nitrogen, apparently. No liquid phase, though, at least not on the surface: it goes directly from ice to vapour and back.

  4. Pingback: I wonder … | Zoopraxiscope Too

  5. And I might add that another child is quite acceptable to thriving in volcanic lakes… the much aquafarmed Tillapia. For the Google Earth explorers, lake Taal has numerous Tillapia pens. They are the rectangular boxes that you can see in the lake images.

      • Yeah, the bane of doing stuff from a Cell Phone. 😀

        Generally, when they have a Tilapia die-off, those who understand what it could mean start freaking out(SO2). The last time, it turned out to be storm water run-off that shocked the fish with cold temps or fertilizer byproducts.

  6. Cheers and happy weekend everyone 😀

    All the quakes in Nýidalur makes me verry curious about that area these days.
    And don’t you worry Bardarbunga. You have my attention to as allways.

  7. … and an unconventional resource for you volcano watchers.

    http://www.blitzortung.org/Webpages/index.php?lang=en

    This is a volunteer lightning detection network. How does that apply? Well, if an eruptive plume occurs, it will typically be accompanied by a large number of lightning events. In the meantime, you can sit back and enjoy watching the various strikes from the thunderstorms.

    • That’s really cool. Not just seeing it in one region, but around the world.

  8. Enjoyed the article. 🙂

    Here’s an article from EarthSky talking about molten magma that’s now solidified on the moon.

    http://earthsky.org/tonight/believe-it-or-not-moons-near-side-is-dark-side?utm_source=EarthSky+News&utm_campaign=f01a7df13c-EarthSky_News&utm_medium=email&utm_term=0_c643945d79-f01a7df13c-394269541

    Tonight is a lunar eclipse. It’ll be a total eclipse for the eastern US. It’ll be the 4th supermoon this year & a harvest moon. It’ll be reddish in color, which is why many of us know it as a blood moon. I hope the clouds clear here. Here’s more info about it from NASA:

    http://science.nasa.gov/science-news/science-at-nasa/2015/22sep_lunareclipse/

    • There is also a big NASA announcement tomorrow. I am pretty curious what that will bring.
      My bets are on liquid water being found on Mars..

      • That seems to be the consensus, based on who will be present at the press conference. Liquid water can’t exist on the surface but under some conditions it can be present subsurface. The other big question they could try to answer is where the methane on Mars comes from. But that is less likely.

        • 2020 here in NE Oregon. 12C and a hard gusty, West wind. unpleasant to be out/moonwatching. Totality starting to wane .
          really dark eclipse. Wife and i went tout to the local airprt to watch the moon come up over the Wallowa mnts. 3000+ meeter peaks to the east. the moon came up in a crescent shape! then quickly headed into the
          Earth’s penumbra…
          BTW I think water on Mars is the likely NASA
          announcement..

          • Sorry about the spelling errors have remnant a cold writing between coughing fits…

          • The moon was really dark up here too. Probably because of cloud around the pacific stopping the light getting through to the moon?

          • The clouds here broke up enough to watch the moon last night. We had a good view and weather here was nice to sit out to watch it.

  9. You’re a born writer! I’ve really enjoyed this story, thank you!

  10. Hi all, i found you again.
    i have a question and just wondered if someone would do a write up on it
    Mauna Loa
    There is increased activity but its hard to find anything that would help decide if this is looking likely to come alive.
    I have looked at the GPS and tilt and webicorders but unable to make much of it.
    What are we looking for in these.
    What is estimated increase in magma considering the inflation.
    What is most likely increase before expected eruption and where and what would we expect in noise showing.
    I am hopefully off to big Island in two weeks, not expecting anything of course but wondering if later this year could be the time.
    I believe its well overdue
    Some help monitoring this and some expert opinions would be appreciated.
    My last visit was 2013

    • I think Mauna Loa is still far from an eruption. There has been some inflation and small earthquakes. GPS shows that a magma reservoir underneath the caldera is refilling. But this happened a decade ago as well and nothing came from it. Eventually there will be an eruption, probably around the southwest ridge. But from what is going on at the moment, there is no strong indication this will be anytime soon.

      But a volcano can change its mind rather quickly!

      • They raised the alert level for reasons; look at the changes of slope on the GPS graph.

        I have no sense whatever of what the timing might be; more likely months or years than weeks.

        No volcano is ‘overdue’ of course – but this is especially true of Mauna Loa. It erupted quite frequently 1850-1980 or so – but this was an *atypically* high frequency of eruption if you look back at the longer record. What we’re seeing now appears to be a return to its ‘normal’ lower frequency style: long periods of relatively low eruption frequency; shorter periods of relatively higher frequency.

        • Thank you everyone for replies, The fact its on yellow advisory does make my trip a little more exciting. 2 years ago i took a helicopter ride over the Volcanoes and was fantastic looking down into the red glow inside our planet. The devastation over the years is huge with large areas of lava covering many Km all over the island. The quakes do seem to have quietened somewhat in last day or two but its the small quakes that they are unable to plot that makes it unknown if this is complete picture.
          Im struggling to get any real data the web corders not showing on my computer , previously i had them but last two days i just get a “?”
          So looking for any data.
          I am a complete novice compared to most on here and any input is always appreciated.

          • Hi Floodwarn and welcome back! Taking a quick look at the data:

            * With the exception of the swarm at 5-13 km depth (red) at the end of July, which led to a substantial increase in the cumulative seismic moment, eqs seem to be confined to surface adjustments and not magmatic.

            * The “Cross-caldera Distance Change: Past Year” with a total increase of 45 mm accompanied by an “upwards” movement of >6 cm would indicate that the (shallow) magma reservoir is recharging at a slow rate. Just how much this would have to change before an eruption would be “imminent”, I have no idea.

            In all, I’d say (amateur opinion) that there is very little chance of Mauna Loa erupting while you are there. Kilauea now, that’s a different matter. 😉

          • Thanks karenZ and henrik for replies since last visit.
            tonight we have some bigish quakes about 4km deep on mauna loa but its the small quakes which are running at about 20 a day
            I suspect most are from the swelling of the mountain and so tetronic as you say, but some have been deep too. 4km could that mean Magma is moving upwards?
            regarding kilauea having seen it in the past it always amazes me, but mauna loa is the big one
            any thoughts on latest (todays) events as i await the next update in next few hours

  11. There is an earthquake swarm in south Iceland right now.
    Through nowhere near a volcano. Nor does Maps show any long forgotten craters on the ground.

    Probably tectonic. Thought don’t take my word for it.

      • Sorry. Misread the scale on the map; should be +/- 20 miles. But there are volcanic features closer than Hekla.

        • I agree Mike & others: Take a look at the IMO map and you’ll see that the entire area is suffused by “sprungur” or faults. That’s the graben known as the South Iceland Seismic Zone, SISZ. Note how well the N-S distribution of quakes fits the pattern!

          That said, rifting at the Reykjanes Ridge (MAR, Mid-Atlantic Ridge) has gone on for years now and earlier this summer people within the IMO confirmed to Carl that there was a 50-50 chance of an eruption (I’ve only got Carl’s word for it). Even if there has not been a full-scale rift eruption there, it would be strange if the action didn’t translate through the SISZ towards Hekla. However, this is the “surface” action near the top of the crust. What goes on at the bottom and just below in the Astensosphere, who knows?

          • Oh, it was a couple of months back when we had that huge swarm (end of June, beginning of July).

  12. Another 4.2 at Sheldon (Nevada) just now, as the ongoing activity seems to be increasing both in intensity and depth. Here is the drumplot for LVW from the PNSN which shows another 4.2 from 9-27 (~2 days ago). Not only does it show the earthquake, but what I believe is a prolonged period of tremor due to magma movement. The depth of these last two big quakes is also deeper than usual, also a possible sign of magma moving up from depth.?

      • Nope no fracking there, it is all high lonesome like most of Nevada and Eastern Oregon, and southern
        Idaho and Utah, and ….
        antelope, cattle some sheep and few humans…
        I’ve held it is volcanic in nature for months.. We will see…

        • @ TJ, Are you aware of this blog from the PNSN?
          http://pnsn.org/blog
          There are some opinions being expressed that Sheldon has a magmatic component. Lastly, this morning there was a 1.3 event at 15.8km depth, which I think is the deepest so far.

          • Yes i was aware of that post, but am having problems with their site this a.m. kept getting a 404 -seems to be ok now.
            What is interesting is the depth and nature of the quakes that you referred to . I wonder too if there is going to be some sort of rifting event. as this appears to neatly on or very near the Eugene /Denio
            fault zone. A Wiki on the whole
            of the Brothers Fault zone :
            https://en.wikipedia.org/wiki/Brothers_Fault_Zone
            Eastern Oregon is an amazing jumble of fault zones terrane and volcanics..
            My guess that if this area ever erupted , would be Basaltic in nature, as are most of the previous eruptions,,,,

      • Not that I’m aware of. SInce Sheldon is in the middle of the Sheldon Antelope Preserve, I would doubt any mining or other explorations are there. The swarm is now 1 year and 3 mos. and ongoing. http://www.seismo.unr.edu/Events/main.php?evid=512749
        Nevada Seismo Lab is still sticking with their explanation that the activity is due to an unusually long sequence of extensional (normal) faulting which is typical east of the Sierra in Nevada. However, there are also several signs that magma is involved. Notice the clustering of activity at 8-10km deep. The general profile of focal point depths sure looks like a magma chamber to me.

    • Perhaps it was held up by all that water?

      If the water is from the caldera. I wonder if they are going to test the water chemically? It could tell something about all those small sub glacial eruption rumours that went around during the eruption.

      Its odd there aren’t that many quakes though. Its hard to believe a caldera can drop 3 meters with little or no quakes. After seeing the constant ring the small gradual drop back then created.

      Still, Volcanoes can be influenced by pressure changes so I think the next couple of days are going to be quite interesting.

      • It’s the level of the ice in a cauldron that is dropping, not the caldera? On the other hand there have been eqs consistently in the area since before the eruption last year. Not sure, though, where the cauldron affected is on Vatnajokull.

        • The cauldrons in question, most likely belong to the Hamarinn hydro-thermal system.

    • 2½m over the past 24 hours combined with the news of a glacier flood. Culprit identified, I’d say.

      • …am I to understand that the GPS station is on ice? I thought they picked out rock outcrops for the stations.

        • Hope it floats. I’m trying to imagine what this sink hole looks like. Do they do fly overs? Probably difficult to get a good pic of white-on-white.

        • If they were looking for a potential Jökulhlaup, especially after recent activity at Bardabunga and Holuhraun, I guess they would put the station on the ice above where water might drain to and later source the Jökulhlaup?

  13. Almannavarnir ‏@almannavarnir 13m13 minutes ago
    Uncertainty phase declared due to the possibility of a fast rising flash flood in Skaftá, S-Iceland, 1/2

  14. Gisli Olafsson ‏@gislio 33m33 minutes ago
    Scientists expect the glacial flood from #Skaftarjokull to occur late tonight #Iceland

    • “The present level of subsidence exceeds 11 m, but this represents only 10% of the expected total. In the coming days, the rate of subsidence will continue to increase.” From a specialists remark at
      http://en.vedur.is/#tab=vatnafar . 30 Sep 15:25 GMT

      Thats quite a drop!

  15. On the IMO hydrology front page, there are two comments that seem to me to be mutually inconsistent. I’ve asterisked the key clauses.

    The speciallist remark contains the statement that “Floodwater is propagating beneath western Vatnajökull to the Skaftá river, where it is likely to emerge early on Thursday morning, 01 October. From there, the jökulhlaup *will take about 4 hours to reach the nearest gauging station at Sveinstindur*.”

    On the other hand, the weekly overview states that “*Conductivity levels increased to 160 us/cm at the Sveinstindur station on the river Skaftá*, but have now dropped again. Data from the GPS-station in the Eastern Skaftá cauldron in Vatnajökull are being closely monitored, the last jökulhlaup from there having occurred in 2010.”

    On the assumption that the conductivity level was taken to be a sign of the jokulhlaup, what puzzles me is how they could have increased *before* the water reaches the Sveinstuindur gauging station. Or perhaps there is no connection at all, and the jokulhlaup was predicted solely on the basis of the GPS signals from the Skafta cauldron.

    Can anyone explain, please?

    • A rise in conductivity indicates a higher concentration of ions in the water as would be expected from water coming from deep within a hydrothermal system where it may or may not have been in direct contact with magma. The increase could thus be a sign of hydrothermal activity that has caused melting on a large scale and the drop that enough glacier has melted to dilute the water, lowering the ion concentration.

    • It may be that the glacier started to leak slightly. Which gradually reduced the integrity until it at one point collapsed completely.

      This first pulse of water entering the system kicked up lose soil which is being measured. But the water eventually became clean again as the stream ran out of lose soil.

      At least that’s how I puzzle things together.

      • Thanks, that kind of make sense of the inconsistency. But if it was loose soil (volcanic dust) from an initial leak, would that have the ionic “content” that would indicate a jokulhlaup – wouldn’t it just register as a greater concentration of the background ions from the soil that’s already being carried in the soil the river?

        Henrik: my difficulty is that for the ions to have a higher concentration and to have been detected they must already have reached the Sveinstindur apparatus, but IMO are saying that the ‘hlaup won’t reach Sveinstindur until later tonight or tomorrrow… (I have also made a comment about your report from Carl, above.)

        • Conductivity measures the ease electricity travels through water. Which then can be compared with graphs from earlier samples to get an idea how polluted it is.

          It wont tell you what the pollutant is or the source of it for that matter. Though the people working there probably get to know their river well enough to make a good guess.

          • OK, thank you for explaining that. As you can tell, I am not a scientist. (Though I did get as far as leaving school the term before doing A levels in Chemistry, Physics, Maths, and Biology. To quote the Grateful Dead: “What a long, strange trip it’s been”!)

            What it seems we are saying is that there can be a small increase in conductivity caused by a precursor event without a full-on ‘hlaup but which is sufficiently different from the normal background level to be a forewarning.

          • One of the indicators of a subglacial eruption or major hydrothermal even is is an increase in the ion content of the water in the rivers. Such an eruption or event could induce large-scale melting and trigger a jökulhlaup at a later time/date. This is why you get the rise in conductivity well before such a hlaup reaches the measuring station. 🙂

            It would seem that with the thickness of the Vatnajökull glacier, a VEI 3-4 eruption is the very minimum required to breach 700 m of pristine glacier and the same can be said of Katla even though the glacier is somewhat thinner in places.

          • Many thanks for that – and for your patience. I understand now – and what I had earlier misunderstood!

  16. If you are planning to be in the area of the jökulhlaup, take note of warnings from IMO, e.g.

    “Hydrogen sulphide is released from the floodwater as it drains from Vatnajökull. The gas is particularly potent at the ice margin, where concentrations will reach poisonous levels. Travellers must stay away from the edges of Skaftárjökull, Tungnaárjökull and Síðujökull while the jökulhlaup occurs.”

    More on http://en.vedur.is/about-imo/news/nr/3203

    • And for those that don’t know, H2S will numb the olfactory nerves and deaden the sensation. It is very easy to become accustomed to the smell and not know you are in danger.

  17. And after this, a major hurricane heading for Chesapeake Bay. I very much hope it doesn’t go there.

    • Really depends on which model wins. On the other hand, it IS Virginia. More of a Karma event than anything else. It might be best to avoid this while it makes landfall.

    • The last flood was in 2010? so 5 years to accumulate plus any extra water which may have come from activity near Bardabunga (latter is speculation)?

  18. Alert phase has been issued due to the glacial flood in Iceland.

  19. I seem to recall august 2014 reports of water moving under/within vatnajokul. Left as a mystery to my memory. Anyway connected here?

  20. WoW. Something just shaked in Iceland that left a tremor pulse troughout the stations in and around Vatnajokull. Could be perhaps related to the flood, but the output and subsidence were not out of the ordinary.
    You can see the tremor pulse in the brownish color on the bottom of the drumplot.

    It is also seen nicely on the tremor plots as a strong spike of low to mid frequencies. Also seen nicel is the tremor caused by the flood.

    [img][/img]

    Something definetly moved/shaked under Vatnajokull. More precisely somewhere around Bardarbunga. It could be the glacier due to the emptying lake. Interesting anyway.

    • The trident tremor pulse was joined by a mid deep M2+, both of which were located at Bardarbunga, given the signal amplitude and arrival times and IMO automatic quake detection system. That tremor pulse could be magma movement inside the Bardy caldera.

      • Neither of the two long duration events (at 19:00 UT and 01:15 UT) are visible in the icecap GPS. The GPS does show other quakes. My guess would be that a part of the ice cap blocking the outflow gave way. The GPS shows that the collapse slowed down markedly before, which may mean that the flow became partially blocked. The collapse has now resumed.

      • Could the pressure release from the water draining raise the possibility of an eruption at BB?

  21. False color imagery seems to show the storm bumping into something…. possibly an old front. This supports the models that indicate it being slung out to sea.

      • Probably is aware that I am not easily impressed…

        On a whim, I added a few more packets of barley to my stores. If push comes to shove, I’ll roast them and brew up a batch of beer.

        What does impress me, is that containerized cargo vessel that put to sea and headed straight into the storm. USCG is trying to mount a search and rescue operation to find the survivors. That whole thing reeks of insurance scam. A 15 degree list going into a hurricane is not a wise move. Anecdotal word is that it was already a decrepit hulk prior to putting to sea.

        I’ve made pretty much the same trek on a USN Cruiser… but it wasn’t a hurricane, it was a forming NorEaster that traveled on up the coast. Many cookies were hurled that night. I found out later that a cousin of mine was on a cruise ship further out and had to ride the whole damned thing. I laughed my ass off. I know what she had to go through. 😀 All night long we sat up in CIC listening to a passing NATO flotilla that was desperately trying to coordinate getting their smaller ships to safe harbor. We wound up in the storm by accident. The only reason we were at sea were for engineering drills. Yeah, it was rough, but nothing like the actual hurricane that ran our ship (at the time) out of Pearl Harbor. (circa 1983) The Goldsborough was behind us as we left port and suffered casualties during her Sea and Anchor detail. Our damages were an anchor buoy that washed over the side. It was too rough to let any of the B’osuns try to go out and retrieve it. One place you don’t want to be is on the Forecastle the bow plunges into a wave.

        USS Ramsey “Second to None!
        (First to nobody and third in a class all by ourselves…)

        • meh. being an aviator, I always wondered what commercial maritime would do to miss a storm.

          when I saw that marinetracker image, my first thought, it was either an intentional act, or the master was totally blind.

          as an aviator, the one place you did not want to be directly pointed was at the heart of a storm. the earlier a course correction can be made. the shorter the length of the diversion.

          on the other hand, with 40ft seas coming abeam would make it a vomit bucket for sure.

        • Just as well given the information conveyed by Lurking about Virginians and knowledge of what constitutes the favourite pastime of people “holdbound” during a severe storm.

          • The Island, Normally go to mauna kea and of course Kilauea. Staying in Waikoloa Mauna Loa and Mauna kea are clearly visible. I did not climb Mauna Loa last time but who knows this time.
            everything just seems more interesting when your going there.
            But i agree that unlikely to see Eruption this month and anyway i am not that Lucky.

          • I have been at Waikoloa although not since the earthquake. Mauna Kea is interesting (but you won’t be allowed to take a rental car up there). I don’t know whether there is any access to Mauna Loa. If there is an eruption, the access road to Mauna Kea and of course Mauna Loa has a chance of being cut.

          • Can take hire car up there if 4×4 did it two years ago and parents are there now as they got their own place there. Must be 4×4 thou for Mauna kea. Volcano centre thou is a long drive 250m round trip

  22. The tremor pulses continue with a decent amplitude. More than likely due to the flooding. Could be due to changes in the glacier itself. The signal seems to be coming from around the Bardarbunga/Hamarinn area. The frequency of the tremors is actually quite in the mid to low range.

    • Given how the new M2+ looks like, the one that emerged just now in Bardy, its kinda obvious that it is emerging from the similar region as the tremor pulses, and just like yesterday, the recent tremor pulse was followed by an M2+ in Bardarbunga. Very soon after this M2+, a new tremor pulse emerged almost instantly from Bardarbunga area at 21:30, sending a loud signal across Vatnajokull and beyond.

      • Looking at the Iceland drumplots, there was a rather peculiar movement (blue line) lasting five minutes from 13.10 today on the Urdarhals plot. I can’t see it recorded on any of the local drumplots yet, so maybe it was very localised and shallow – so I’m guessing it was a glacier-quake or avalanche – maybe a serac dropped down the cliff or something.

        • Just looked again and the blue line is now green ‘cos they have changed the start times in the left-hand column… just saying ‘cos I can’t edit my own post.

  23. Activity may be picking up at Mauna Loa
    Lots of quakes in last few hours
    Although i am aware of the military zone near by
    here is the web corder, any comments?

    • Depth 0.0 km very rarely corresponds to the local surface, but rather to a reference point zero which means the hypocentre of the quake (3D-position) may actually have occurred quite some distance below the local surface. Without knowing what the actual z-coordinate of the reference point is, it’s impossible to say exactly where it occurred and hence, what may have caused it. 🙂

  24. So am i correct in thinking that if it turns out to be deeper (significantly) then it was probably stronger than suggested too.

    • The listed magnitude should be fairly accurate. The depth is normally igven as either with respect to sea level for distant measurements, or with respect to the height of he detectors otherwise. For Mauna Loa, I expect that the detection occurs on the mountain. Are you going to Mauna Loa itself or to the island?

  25. Urdarhals drumplot has some odd – looking quakes today which don’t appear on nearby drumplots, nor have they appeared on IMO earthquake tables. The times are 13.10 (and lasts about five minutes) and 18.10 (again lasts a few minutes).
    Bardabunga’s 3.1 this afternoon shows on the Urdarhals drumplot but doesn’t look any more pronounced than the other ‘quakes mentioned above, which suggests to me that whatever caused the odd – looking ‘quakes must have been very localised… but what was it?

    ?0.41621593530532053

    ?0.4695559591184919

  26. Sorry, I think I made a booboo and the above graphs courtesy of IMO are ‘live’, so the relevant bits will disappear soon -_-

  27. Local seismicity from isostatic rebound? Suddenly removing 100 tonnes per m2 of ice, something has to happen. It might only be 10% or less the load from ice age glaciation and a small area, but it was removed almost instantly.

    • In principle, yes, removing weight does help eruptions get going. Less pressure allows more melting to occur. But this is too small to make such a difference. Remember that is only one cauldron, and the weight is actually distributed over a much larger area, when you get deep down. These events happen every few years and don’t trigger eruptions (but they can be triggered by subglacial eruptions, of course). Were the whole glacier to melt, that could make a difference. We may know in a century or so.

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