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EESA06H3 (568)
Nick Eyles (500)
Lecture 4

Lecture 4 Notes

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Environmental Science
Nick Eyles

EESA01 CLASS 4 Embryonic Ocean, a new ocean: Red Sea Rifting through young oceans and closing because the floor of the oceans become sub ducted The floor of the ocean crust, as you move away from the mid oceanic ridge, the thickness of the oceanic crust increases because it is cooling away from the ridge Thick heavy rock on the mantle below will result in it sinking back into the mantle New ocean forming pushes the lands apart The history of the continent is dictated by the history of oceans If we look at the Atlantic there is a spine that runs up the middle of the Atlantic which is called the mid ocean ridge. They are under water volcanoes and they are active all the time. To accommodate the new volcano material, it pushes the North American and European plates apart. _____________________________________________________________________________________ 1. INTRODUCTION TO MIDOCEAN RIDGES: MODERN AND ANCIENT FOSSIL MORs (CALLED OPHIOLITES) When ocean close, the floors get pushed up on landophiolites By looking at the rocks and structures, we can see the processes of ocean life They are important economically, because they are mineral rich; oceanic crust ancient pieces of ocean 2. WHY ARE MORs FRACTURED? THE ROLE OF TRANSFORM FAULTS The mid ocean ridge is not strictly continuous, there are cracks called fractures These fractures enable ocean floor spreading on the curved surface of the earth Dikes or dykes are orange strikes on rocks (picture with his motorcycle) They are the result from hot magma intruding into older rocks along fractures As this happens, the rocks are being extended and pushed apart. This is the basic behind plate tectonicmovement The continuous feeding or magma and dikes Sheeted dikes: so many closely spaced dikes When the magma reaches the ocean floor it cools very rapidly and we find the pillowed lava where the basalt magma was cooled Below the magma chamber we can see Gabbro chemically equivalent to basalt but it has larger crystals because it cools slowly Sheared peridotites equals to mantle. It is made of olivine, green colour. When it is polished it is known as peridot The top section is a vertical section like a snapshot The bottom diagram shows what happens when we spreads the ridge; symmetrical distribution of magma on both sides What is feeding the MOR: ploons Distillation basalt and gabbro are distilled from huge mantle ploons
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