While I’m not a geologist, it’s hard not to be fascinated by the geology of the largest island on earth. It holds a great many mysteries as only 1/5th of the island is not covered by ice.
The geology is ancient; most of Greenland is dominated by crystalline rocks and is part of the Precambrian shield, going back more than 3 billion years. That’s billion with a b. Some of the oldest rocks on the planet are here in Greenland. And they’re everywhere.
If you’ve hiked Michigan’s Upper Peninsula, northeastern Minnesota, or even the northern-most part of my home-state, Wisconsin, then you’ve tread on parts of the Precambrian shield. A vast area of exposed metamorphic rocks like: gneiss, schist, and quartzite; formed billions of years ago from igneous rocks when the area was originally volcanic. The Precambrian shield is also known as the Canadian Shield or Laurentian Plateau.
The eastern side of Greenland is geologically quite different from the rest of the island. While the basement rock is still Precambrian, it has been reshaped by the splitting of the Atlantic basin. Piled on top of the basement rock are up to 6,000 feet of sedimentary rock giving many of the mountains their ‘layered cake’ appearance. Also mixed in are huge basalt columns, like you’d see in Wyoming’s Devils Tower. The columns are evidence of volcanic activity from the spreading of the Atlantic plates.
I've tried to include some other interesting geology in the captions below. If you have kids, or are still a kid yourself, start a rock collection from all the places you visit. We have one that wraps around the house. The limit on my international luggage is 28 kg, but a couple 3-billion-year-old rocks might be making the journey.
A short movie of the Watson River as it flows through Kangerlussuaq. The river has cut a channel in the ancient bedrock, probably exploiting a fissure, and time, water, and freezing/thawing have created the channel. And the end of the shot you get a nice view of how the gneiss has been worked and carved by the sediment carried in the high velocity flow. How long would you have to scrub a spot to form a 'pocket' like those? Finally a view of the great outwash plain as the river empties into the fjord in the distance.
Thanks to Al Fleming for all the geology help in this journal!
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