Land+Forms

Mountains are formed when tectonic plates push together at convergent boundaries.two continental plates collide push up wards to form a mountain.



Rift valleys are formed when A new ocean begins when hot mantle material begins to move upward beneath a continent. Geoscientists are still not certain about why that happens. The lithosphere of the continent bulges upward and is stretched sideways. Eventually its breaks along a long crack, called a rift. Magma rises up to feed volcanoes in the rift. As the rift widens, the ocean invades the rift. A new ocean basin has now been formed, and it gets wider as time goes on.

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  Examples of island arcs created in this way are the Aleutians, the Kuriles, Japan, the Ryukyus, and the Philippines, found clustered around the northern and western borders of the Pacific Plate like a necklace. There are other island arcs to the south (Indonesia and the Solomon’s), and although scientists are still puzzled by the exact origin of these southern island arcs, plate subduction is the suspected architect. [] ||
 * Island Arcs ||
 * The journey of a plate sinking into a trench is a long and complex affair, and the effects of this journey are apparent on the face of the earth. Firstly, as the cold, stiff plate begins its arduous descent, a continuous series of earthquakes is created. The plate then starts to heat up and at a depth of about 75 miles, certain magmas are melted and rise toward the surface. Eventually these magmas make their way up into the leading edge of the overriding plate, where they add material to the crust and build volcanoes above it. If the upper plate is oceanic, the volcanoes pile up until they poke through the surface of the ocean and form an elegant arc. [Scientists believe that this arc formation has something to do with the curvature of the earth].