The Geikie Plateau lavas
The Eastern coast of Greenland starts off somewhat smooth, traveling northeast from the huge island’s southern tip, with only occasional outlet glaciers draining the large icecap. It then reaches one more tip, a Peninsula holding what is known as the Geikie Plateau, before turning due north with a much more dissected, channel-filled coastline.
These rocks come from the Geikie Plateau and they illustrate some of the processes that went into forming Greenland as it exists today. These layered rocks are the remnants of a huge outpouring of lava about 60 million years ago.
These rocks date back to the time when the northernmost Atlantic Ocean opened. The continents were spreading to the south well beforehand, but Greenland finally pushed away from Scandanavia and Scotland at that time. The fairly sharp coastline along Southeastern Greenland is a testament to this fairly recent geologic event; there hasn’t been much time since the ocean opened for deeply incised channels to form, leading to a fairly smooth coastline still partially defined by the locations of tectonic rifting.
A thick pile of lava like this doesn’t make it to Earth’s surface easily. These rocks bear chemical signals suggesting that they relate to the Icelandic Large Igneous Province or the Icelandic plume – the same surge of magma that built these rocks today builds Iceland to the East.
A big blob of hot rocks wants to rise up towards Earth’s surface, but it can have a tough time getting there if a continent is in the way. Sometimes the continent will melt, sometimes the continent can even be pushed apart.
Since these rocks formed at the same time the ocean opened, the continent itself was probably wedged apart and pushed open by the hot, rising mantle that melted to form these thick lava sequences that now dot the Greenland coast.
The final ingredient here is, of course, ice, which has sculpted the terrain. Sharp shapes like the mountain at the center are called horns: they are carved by glaciers that flow down all sides from a central peak. The valleys in the foreground are snowed in, but at the bottom its almost certain that their bases would have a U-shape, carved by the weight of huge glaciers moving through them during previous ice ages.
Image credit: https://www.flickr.com/photos/gsfc/7166013678/
photos by orsolya haarberg in iceland
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