Raining ash

19.05.2015
Christian Magnus (text and photo)

A young Jan Steinløkk from the NPD in front of sediments at Fur on the Lim Fjord, laid down 55 million years ago with light layers of shelly fossils and darker stripes of volcanic ash.

A young Jan Steinløkk from the NPD in front of sediments at Fur on the Lim Fjord, laid down 55 million years ago with light layers of shelly fossils and darker stripes of volcanic ash.


Lava and volcanic ash erupted 55 million years ago from fractures which would later become the North Atlantic. Greenland lay adjacent to the NCS at that time.

Drilling in the old volcanoes beneath the Norwegian Sea and all the other wells off Norway have provided much information about this period of geological history.

Ash from the eruptions was carried near and far on the winds. Sub-surface arms from the volcanoes penetrated between the thick layers of sediment deposited in the Vøring and Møre basins.

Heat from the magmatic chambers, the volcanoes and their long vents meant that large quantities of gas previously contained in clay and sandstones were blasted out of the ground.

The methane in this blowoff, combined with much carbon dioxide, caused a dramatic rise in temperature for a brief period just a couple of million years. Fortunately for Norway, the huge quantities of lava and igneous rocks in the Norwegian Sea dating from this time are a rare phenomenon.

A similar period of large-scale volcanic activity occurred in Siberia at the end of the Permian, when 90 per cent of animal and plant species died out.

Things were luckily not quite that bad 55 million years ago, at the transition from the Palaeocene to the Eocene. Remote ancestors of hippos browsed in the sub-tropical landscape of what is now the North Sea but was then partially dry land. This was just a brief tropical episode in Norway’s geological history.

Today, the volcanic ash lies beneath a layer of sediments deposited after the vulcanism had ceased, and has largely been converted to viscous clays known as the Balder and Tare formations in the North and Norwegian Seas respectively.

The small picture depicts microscopic shelly fossils of marine algae. The other shows sediments dating from 55 million years ago, with light layers of algal shells and darker stripes of volcanic ash. Both hail from Fur on Denmark’s Lim Fjord.

 

Electron microscope image of shelly fossils from Fur.

Electron microscope image of shelly fossils from Fur.

 



Topics: Geology