Living on a constantly changing and evolving planet, unravelling the past is not an easy task as resurfacing, erosion and continental drift continuously eradicates what has gone before. Even after the last remaining “White Areas” on our maps of the Earth’s land masses had been filled in about a century ago, great discoveries that would change our perception of our planet were made as technology made them possible. It is perhaps hard to imagine, but only a little more than 50 years ago, the Ocean depths were in main completely unknown.
When the German meteorologist, geologist and astronomer Alfred Wegener put forward his hypothesis of continental drift in 1912, such was our lack of knowledge about our own planet that half a century would pass before proof that would ultimately confirm it was found. In the early 1950s, paleomagnetism was recognised a new (branch of) science and by early 1953, samples taken from India showed that the country had previously been in the Southern hemisphere as predicted by Wegener. Even without the great advances in knowledge that the Space Age would bring, the theory had enough supporting data that opinions were starting to change, and in 1964, the Royal Society held a symposium on the subject. Wegener had been proven correct.
The Space Age and the Cold War surveillance technologies that were developed as a result were to bring the next great step in our understanding of our planet. As late as the 1960s, it was generally assumed that volcanic eruptions such as those of Thera (~3.65 kA BP), Vesuvius (79 AD/CE) and Krakatoa (1883) represented an upper limit in volcanic ferocity. However, geologists had long known that Yellowstone National Park was volcanic in nature, but “where was the volcano”? It was not until high-altitude reconnaissance photographs became available that the realisation dawned – Yellowstone was the volcano and one on a scale hitherto not imagined. From this realisation, the discovery or identification of yet more of these gigantic systems became inevitable. Satellite imagery of the Snake River plain revealed that the volcano had been active in different locations for at least 14 million years and might possibly be interconnected with the Columbia River Flood Basalts 17 MY BP.
Further advances in technology, primarily those of computing power, allowed images of subducting continental slabs to be made from earthquake data points. Another technique developed was that of “earthquake tomography” where the times at which earthquakes arrive at an array of seismic stations is compared with a model of propagation and the difference between expected and actual arrival together with the path taken by the seismic shock waves can be used to form a “picture” of what lies underneath a given location. Areas where the shockwave propagation is slower than through solid rock indicates possible locations of bodies of molten or semi-molten rock, i.e. magma. Today, such maps can be produced by a skilled amateur given access to data and the appropriate software as proven by our own GeoLurking or DownUnder to name but two.
Today, the terms “supervolcano” and “supereruption” have begun to gain wide acceptance. On the established albeit inaccurate VEI-scale, supervolcanoes are volcanoes that are capable of a VEI 7 or VEI 8 supereruption. If the measurement of volume DRE – Dense Rock Equivalent – is applied, a VEI 7 eruption falls into the interval between 100 and 999 cubic kilometres of erupted material whereas in a VEI 8 eruption, between 1,000 and 9,999 cubic km DRE is erupted.
What the VEI scale does not consider is time. Volume-wise, the greatest eruptions known on Earth are the Flood Basalt eruptions where several million cubic kilometres are erupted, mainly effusively, but over a scale of millions of years leading to a measly annual average of 1 – 3 km3, a rate achieved by the 2014-5 Bardarbunga/Holuhraun eruption. Certainly, within those million-plus years timeframes, there have been periods of much greater effusion of magma, but the fact remains that even the largest of known Flood Basalt eruptions such as the Siberian Traps (approximately 250 MY BP) are relatively speaking gentle if prolonged affairs with serious effects on both biosphere and ecology. Gentle, at least in comparison to the greatest of explosive eruptions.
The WikiPedia article for supervolcano claims “The eight eruptions at the Paraná and Etendeka traps during the Cretaceous period when taken together were well over 15,000 km³, and may have been a single event that was the largest explosion during the Phanerozoic Eon, but there have been no confirmed VEI 9 eruptions.” Is this observation accurate? Could it not be that we have not looked in the right place yet?
More than a year ago, Carl and myself had a very interesting discussion over a couple of beers or four, on the very same day that the seismic crisis at Bardarbunga broke that would lead to the eruption a week or so later. In this discussion, we talked about the geological anomaly of northern Fennoscandia; the Kola peninsula in general and the Kiruna Mine in Northern Sweden in particular.
Northern Fennoscandia is rich in economically and strategically important metals such as Tungsten/Wolfram where one of two known sources lies on the Kola Peninsula (the other lies in South Africa and as it was not until DU – Depleted Uranium – had been developed as a tank gun penetrator that the strategic importance of the South African mines began to diminish). There are the Nickel mines of Petangi, formerly Petsamo, an important constituent of armour plates for well over a century. At Outokumpu, Finland, lies an important mine of chromium, also used in armour but mostly known as the shiny part on car bumpers and a constituent of stainless steel. In Sweden, you have the Skellefteå Field with large finds of gold and there are also large deposits of Uranium that are not being mined. But the incomparable centrepiece is the the Kirunavaara – Luossavara Iron deposit in northern Sweden.
The Kiruna Iron ore body is different from every other known Iron deposit on Earth, in sheer volume, composition and origin. The dimensions of the body of ore are 4 kilometres (2.5 mi) long, 80 metres (260 ft) to 120 metres (390 ft) thick and reaching a depth of up to 2 kilometres (1.2 mi). This mine alone could supply mankind’s needs of Iron for well over a thousand years even if there was no recycling or iron mined anywhere else in the World. It was indeed of such strategic importance that it blinded both British and French strategists during the first year of the Second World War as they, erroneously, considered that depriving Germany of access to the Swedish ore would cripple the German war effort and, hopefully, force a negotiated peace settlement.
Leaving history behind, where other deposits are thought to be the result of microbial action in the primordial oceans of Earth which deposited iron oxides on the ocean floor, the Kiruna deposit can only have come from the Earth’s core and is the result of what Carl terms “a Core Plume”. As the iron body consists of an average of 60% Iron, which in some locations reach up to 78% or more, this effectively excludes any other origin (according to Carl).
So what forces would have been involved to hurl a fragment of the core of our planet to the surface some 1.88 – 1.9 GY BP? One rather inescapable conclusion is “immense”. It would certainly dwarf any other identified eruption into insignificance, especially if there is a connection with the other unusual mineral deposits of Northern Fennoscandia. Here, the term “Hypereruption” is definitely justifiable.
PS. Over at VolcanoHotspot, former VC-contributor Agimarc has posted an excellent article on Kuwae, one which I highly recommend: