We tend to think of earth's land masses as being
fixed in place. But in reality, they are
attached to moving tectonic plates that constantly jostle for position
and slide over the more viscous mantle beneath case in
point Iceland, volcanic eruptions are common on this young
land mass driven by the two tectonic plates that divide
it and by its location above a hotspot, an
upwelling of magma that protrudes from deep in the mantle
up to the crust. This hotspot fuels Iceland's eruptions
today, but millions of years ago, it was
situated beneath neighboring Greenland. Now, a NASA scientist
and her colleagues have used anomalies in Greenland's crustal magnetic
field to derive its geothermal heat flux. The researchers
also analyzed gravity data and other geophysical information to effectively
peer beneath Greenland's kilometer thick ice sheet and into the
crust itself. What they found was a thermal track
in Greenland's bedrock that records the motions of a continent
over geologic time. Greenland is part of the North
American tectonic plate for tens of millions of years.
The plate's movement pushed Greenland over the hotspot when the
hotspot emerged at the Denmark Strait. It began raising
the sea floor to form Iceland today. A channel
of warm bedrock marks the ancient path of the hotspot
. A reminder that nothing stands still over geologic time
and that even the largest land masses are constantly being
reshaped by our dynamic planet.