Presentation on theme: "Sam Videlock. The Oceanic crust is made up of three layers. 1 st Layer – consists of unconsolidated or semi consolidated sediments, sometimes including."— Presentation transcript:
The Oceanic crust is made up of three layers. 1 st Layer – consists of unconsolidated or semi consolidated sediments, sometimes including volcanic ash. 2 nd Layer – Layer two is about 2 kilometers thick mostly made up of glassy Basalt. 3 rd Layer – this layer is formed by slow cooling of magma. About five kilometers thick.
The Volcanoes that create Basalt are very common, and they tend to form in ocean basins. This is a main reason why Basalt is so common inside of the oceanic crust, because all of the cooling magma sinks into the crust, and dries there, creating magma to enter the crust. Picture http://lh4.ggpht.com/_3b1u2R PUEmA/R6S15mIlSiI/AAAAAAAA Alw/HeaLyK5wApM/Lava+Ocea n+Entry_Volcanoes+NP,+Big+Isl and,+Hawaii.jpg
When The basaltic lava erupts under the sea, the lava will cool very quickly. Leaving a flexible skin on the surface, but still molten inside. The molten lava will soon break up into separated groups, until it settles and dries. In the picture to your right, this is under water lava flow. Pictures – http://oceanexplorer.noaa.gov/explorations/06fi re/background/volcanism/media/pillow_lava_6 00.jpg
Most black sand beaches, like the ones in Hawaii are formed when hot basalt lava flows into the sea and is shattered into many fragments when the rock chills. This is similar to the underwater lava flow drying process. The picture to the right shows a black sand beach, and when you really look, you can see the small fragments of basalt rock. Picture http://www.cs.berkeley.edu/~artin/Pictures/Ha waii2005/MauiBlackSandBeach1.jpg
As the hot flowing magma begins to cool under water, it forms a skin like texture that distorts, and stretches into rope like shapes, this is called, Pahoehoe. This picture shows Pahoehoe. Picture http://upload.wikimedia.org/wikipedia/commons/ 8/89/Ropy_pahoehoe.jpg