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I s su e 4 4 • 2021
Iceland’s First Mantle Eruption in Historical Times
Geologist Haraldur Sigurðsson says the eruption is a major breakthrough for earth sciences
“T
he eruption in Geldingadalur m a r k s a t u r n i n g p oi nt i n geological histor y, where scientists get an insight into the Earth’s mantle beneath Iceland for the first time. I have never seen any thing like it in Iceland. This is the f irst Icelandic mantle eruption in historical time. It is unusual and remarkable that the magma does not come from the crust but from the mantle at a depth of 17-20 kilometres”, says Iceland’s best-known geoscientist, Haraldur Sigurðsson in a conversation with the Icelandic Times from Rhode Island in the USA. He says the eruption was of great importance for geoscientists to view. “The earth is like a hen’s egg, with three layers in similar proportions. The
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white is like the mantle of the earth. The earth’s crust is in the same proportions as the shell of the egg and the hot core inside. The magma that is now emerging contains a lot of carbon dioxide CO₂ and sulphur, high temperatures and low viscosity. We know the lava flow from magma chambers well, but the lava flow erupting in Reykjanes does not come from there but from the top layer of the mantle. The continuation of the eruption is, of course, speculation, but this could be the formation of a mound like Skjaldbreið (1,060m), which was formed hundreds of years ago, but the eruption now could last for a short time.” Haraldur says that Krýsuvík has moved about sixteen centimetres to the east and eight centimetres to the north.
PHOTO PÁLL STEFÁNSSON
Higher temperature than a normal eruption
“The mantle is much hotter than the crust. From the mantle comes this special hot magma that contains large amounts of carbon dioxide. We are seeing a bubbling like a pot on the boil and it is difficult to predict what will happen next. The Geldingadalagos eruption is the first on the peninsula in almost 800 years.” Haraldur says the volcanoes are not connected, but many of them lie in a line. “There is a lot of gas in the magma. As the magma approaches the earth’s surface, the carbon dioxide is released and foams, so the volume of the magma increases. It swells like a milkshake and flows to the surface with bubbling gas and turmoil.”
