Greenland’s underground drives thermal activity in the Arctic | Polarjournal
The “Beerenberg” is the northernmost volcano on the Earth’s surface. From a ocean depth of around 3,000 metres, it rises another 2227 metres above sea level. It is nourished by a mantle plume that sits at a depth of about 450 kilometres in the upper part of the Earth’s mantle. This plume is also fed from Greenland. Picture: Hagman – Own work, CC BY-SA 3.0

The volcanic activity in Iceland is famous and stems from the location of the island at the edges of the mid-ocean ridge. The island of Jan Mayen is also known for its active volcano. At both places, so-called hotspots are at work, where liquified rock is pushed up deep from the earth’s interior. Now Japanese researchers have found that deep beneath Greenland’s ice sheet, such a site is likely to be located and has implications for the island itself and other parts of the European Arctic.

The Japanese research team, led by Dr. Genti Toyokuni of Tohoku University in Sendal, Japan, found in their research that under Greenland lies a huge mantle plume, a stream of hot rock material, in the transition zone between the Earth’s core and the Earth’s mantle. This plume, also called Manteldiapir, is connected to the already known plumes under Iceland, Jan Mayen and new Svalbard via hose-like branches and thus feeds a large part of the geothermal activities and volcanoes in the European Arctic. “Knowledge about the Greenland plume will bolster our understanding of volcanic activities in these regions and the problematic issue of global sea-level rising caused by the melting of the Greenland ice sheet,” explains Dr. Toyokuni. The researchers found that the central part of Greenland lies above this plume and they suspect that the warmth of the plume influences the melting of the Greenland ice sheet. The team published their findings in the latest issue of the Journal of Geophysical Research: Solid Earth.

The graphic on the right of Dr. Toyokuni’s work shows the location of the plumes from the centre of Greenland to Iceland (14) and Jan-Mayen (15). Further north, a direct branch of the Greenland plume is also likely to be responsible for the geothermal activity on Svalbard. Picture: Toyokuni et al. 2020 / Tohoku University, Map: Ingo Wöbner, Wikipedia

Geothermal activities in the European Arctic are nothing new per se. The location of the Jan-Mayen-plume and the Icelandic plume were already sufficiently well known. What is new, however, is the fact that these two are connected to the lower Greenland plume via plume tubes, which are part of such a plume. The researchers were also astonished by the result that below Svalbard lies such a plume, which comes directly from Greenland. The results were obtained by the team through three-dimensional seismic velocity structures in the crust and mantle, on which topography structures appeared. A similar principle works for a CT body scan, in which the smallest structures appear. For the first time, the study provides an approach that researchers can now continue to work to find out more about geothermal activity in the European Arctic. The contribution of the plumes to the melting processes of the glaciers in the region is likely to be of great interest.

Mantle plumes have been known for some time. This is liquid rock, which in certain zones between the earth’s core and the earth’s mantle, are pushed upwards partially by the heat. In other places, this liquid rock is formed by subduction, i.e. by the sinking and melting of the material. In certain regions, this liquid rock accumulates in chambers in the earth’s crust and when the crust weakens due to sufficiently high pressure, this material called magma erupts outwards, a volcano is formed at a hotspot.

The video shows how the red ink accumulates from the edge as the water heats up and then rises in a hose to spread on the surface. If you first collect the material in a closed chamber, at some point the pressure in the chamber becomes too high and the material forces its way up. Video: mckenzu via Youtube

Dr Michael Wenger, PolarJournal

Link to the studies:

Toyokuni et al (2020) J Geophys Res Solid Earth 125 (12) P Wave tomography beneath Greenland and surrounding regions: 1. Crust and upper mantle;

Toyokuni et al (2020) J Geophys Res Solid Earth 125 (12) P Wave tomography beneath Greenland and surrounding regions: 2. Lower mantle;

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