Its Like Climbing Under the Ocean

22 09 2012

The continental plates are granite, while oceanic plates are made of heavier basalt. Iceland is unique geologically because it is one of the few places other than the ocean floor that is made of basalt!

We are climbing at the beach, not under the ocean. But the rock here is typically found on the sea floor. The right of the picture is a great example of horizontal basalt, breaking at almost perfect right angles.

Iceland sits astride the Mid-Atlantic Ridge, part of the world-circling undersea mountain system that is the source of new crust formation. Iceland is formed by the spreading boundary of the North American and European plates as well as a mantle plume. As the plates moved apart, excessive eruptions of lava constructed volcanoes and filled rift valleys. Subsequent movement rifted these later lava fields, causing long, linear valleys bounded by parallel faults. The divergence of the ridge started in the north about 150 million years ago and 90 million years ago in the south. Up here in the Westfjords, the stack of lava flows is at least 3,000 m thick. Tertiary flood basalts make up most of this northwest quadrant of the island.

This is Danny leading up one of the routes. The rock here takes some getting used to. Because of the fjords, this rock only sees sunlight a few weeks of the year. It is very cold and slippery. So much so that my hands went numb half way up!

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One response

27 09 2012
veggyval

bomber routes, oceanic crust!
:^)

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