[Rockhounds] Sudden Ancient Global Warming Event Traced to Magma Flood

[Kreigh Tomaszewski]

Roughly 60 million years ago, circulation changes deep within our planet
generated a hot current of rock — the Iceland plume — causing it to rise
from the heart of Earth’s mantle. When the mantle rock pierced the bottom
of the North Atlantic Ocean, lava spurted across Scotland, Ireland and
Greenland, scabbing into spectacular columned landscapes like the Giant’s
Causeway in Northern Ireland and Scotland’s Fingal’s Cave.

That opening salvo was followed 4 million years later by a second gigantic
pulse of hot mantle rock, which once again rode up the Iceland plume. It
swelled under the seafloor and lifted a wide region of ocean floor between
Greenland and Europe into the air, forming a temporary land bridge
connecting Scotland and Greenland.

Under the surface, the mantle blob melted, turning from solid rock to fluid
magma. The magma then bled, bruise-like, through sediments. As the magma
spread, it formed thousands of horizontal sheets known as sills that cooked
organic matter in the sediments. This cooking produced methane and carbon
dioxide gas that burst through vents in the seafloor. As sheet after sheet
of magma bled into the expanding bruise for millennia, more and more gas
bubbled from the ocean like a boiling pot.

Evidence indicates that suspiciously close in time to all that igneous
activity, the planet warmed by 5 degrees Celsius (9 degrees Fahrenheit).

https://www.quantamagazine.org/sudden-ancient-global-warming-event-traced-to-magma-flood-20200319/