00:00 We tend to think of Earth's landmasses as being fixed in place,
00:04 but in reality, they are attached to moving tectonic plates
00:08 that constantly jostle for position and slide over the more viscous mantle beneath.
00:12 Case in point, Iceland.
00:16 Volcanic eruptions are common on this young landmass, driven by the two tectonic plates
00:20 that divide it, and by its location above a hotspot, an upwelling of magma
00:24 that protrudes from deep in the mantle up to the crust.
00:28 This hotspot fuels Iceland's eruptions today, but millions of years ago,
00:32 it was situated beneath neighboring Greenland.
00:36 Now, a NASA scientist and her colleagues have used anomalies in Greenland's
00:40 crustal magnetic field to derive its geothermal heat flux.
00:44 The researchers also analyzed gravity data and other
00:48 geophysical information to effectively peer beneath Greenland's kilometers-thick
00:52 ice sheet and into the crust itself.
00:56 What they found was a thermal track in Greenland's bedrock that records the motions
01:00 of a continent over geologic time.
01:04 Greenland is part of the North American tectonic plate.
01:08 For tens of millions of years, the plate's movement pushed Greenland over the hotspot.
01:12 When the hotspot emerged at the Denmark Strait, it began raising the seafloor to form Iceland.
01:16 Today, a channel of warm bedrock marks the ancient path of the hotspot,
01:20 a reminder that nothing stands still over geologic time,
01:24 and that even the largest landmasses are constantly being reshaped
01:28 by our dynamic planet.
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