Remnant of a plumeCanada is some of the oldest continental crust on Earth, with provinces that are w

Remnant of a plumeCanada is some of the oldest continental crust on Earth, with provinces that are well over 3 billion years old. As a continent sits at Earth’s surface, it occasionally is targeted by something in the mantle below.The mantle occasionally produces catastrophic volcanic bursts called kimberlite eruptions (https://tmblr.co/Zyv2Js1uHBuJ8) and larger outpourings of lava called flood basalts. The latter are thought to be caused by large blobs of hot mantle that buoyantly rise up towards the surface and melt as they reach low pressures.We have several more recent examples of the large igneous provinces produced by these hot blobs of mantle – such as the Siberian Traps, the Deccan Traps, and the Columbia River basalts. Over geologic time though, those thick piles of lava can be mostly eroded, leaving nothing other than the pipes through the continent that brought the molten rock to the surface.Canada is so ancient that it preserves the remnants of several of these pulses of volcanism. They manifest as large dikes – vertical cracks through the ground still filled with solidified igneous rocks. This dike is part of the Franklin magmatic event, a large igneous province that erupted about 720 million years ago. Here the overlying lava flows have eroded exposing the gigantic feeder dike at depth. In other places, such as in the Northwest Territories, some of the lava flows can still be found in tact.-JBBImage credit: Mike Beauregardhttps://flic.kr/p/EykUFCReference:http://link.springer.com/article/10.1007/s00445-016-1012-9 -- source link

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