Unique landforms locate at plate margins Objectives: To understand and be able to explain the location and formation of fold mountains ocean trenches, composite volcanoes Shield volcanoes.
Fold mountains What are fold mountains? Fold mountains are found in many parts of the world. They form along the plate boundaries where great movements have taken place and mountains formed from the folding of the earth's crust.
Describe the formation of fold mountains http://uk.youtube.com/watch?v=ngV66m00UvU&feature=related http://uk.youtube.com/watch?v=jVyBsUgD7Gk&NR=1
There were long periods of quiet between Earth movements during which sedimentary rocks formed in huge depressions called geosynclines.
Rivers carried sediments and deposited them into the depressions. Over millions of years the sediments were compressed into sedimentary rocks.
The rocks were then forced upwards into a series of folds by the movement of tectonic plates. When plates and the continents riding on them collide, the accumulated layers of rock crumple and fold like a tablecloth that is pushed across a table.
Which is the deepest ocean trench? Mariana Trench has a maximum depth of about 11 km (6.8 miles)
At destructive plate boundaries the lava is viscous (thick like treacle) and it cannot flow very far from the volcano’s vent. This makes the volcano steep sided. At constructive plate boundaries the lava is runny and it can flow far away from the volcano’s vent. This makes the volcano gentle sided.