EESA06H3 Lecture 4: Lecture 4 In Class Notes
Document Summary
As the oceanic crust moves away from the ridge, it expands and is thicker due to the cooling process: this leads to the ocean floor to start to subduct. The history of the earth is controlled by the ocean history. Ophiolites are ancient pieces of oceanic crust that gets pushed up on land instead of being subducting under the continental crust. Fossil ocean crust preserved on land: these are rich in minerals. Jokulhlaups: is volcanic activity beneath glaciers (word means to leap from the mountains: causes flash floods. Fractures: are cracks in the ridges, they enable ocean floor spreading on the curved floor of the earth. Dikes: are the result of hot magma intruding into older rock along fractures, thus causing the rock to push apart. Gabbro : is the equivalent of basalt but has much bigger crystals because it cools at the depths around the magma.