Landforms found at plate boundaries
Fold mountains, ocean trenches, mid ocean ridges, shield volcanoes and composite volcanoes
There are 4 basic landforms that you need to know found at plate boundaries. These are fold mountains, mid ocean ridges, ocean trenches and types of volcano. The differences between volcano types can be found here.
Fold mountains are large mountain ranges where the layers of rock within them have been crumpled as they have been forced together. They can be formed at destructive or collisional plate boundaries, where tectonic plates are moving together forcing layers of rock to be crumpled upwards. The layers of rock can form 2 basic features, if the folding is up over the feature if known as an anticline, or down over into a syncline. If the folded rocks in an anticline go over the top of themselves we get a feature known as an overfold.
Chart for the comparison of shield and composite volcanoes
Attempt the gap fill exercise on Fold Mountains
The process of formation is as
follows and can be seen on the diagram opposite;
1) Sediments accumulate in shallow seas or depressions known as GEOSYNCLINES as rivers enter those areas.
2) This creates a sea or lake bed of layered sedimentary rocks as compression takes place.
3) Two plates move together because of convection currents in the mantle
4) This starts to crumple the rocks together.
5) The rocks start to form folds which have anticlines and synclines, which are pushed upwards to form fold mountains.
6) These mountains are then subject to erosion, weathering and mass movement (denudation)
Recent mountain building movements have created the Andes, Himalaya, Alps and Rockies mountains. The Himalaya were created from shallow sea bed sediments under the Tethys sea, which have been pushed up and folded as a result of the Indo-Australian plate moving into the Eurasian plate.
Ocean Trenches are deep water areas that run along a coastline which has a destructive plate margin. They are created by subduction, and mark the point where the Oceanic crust is being pushed under the Oceanic crust. There is often quite a large section of continental crust between this margin and the ocean's edge, and sometimes a volcanic island arc such as Japan or the Aleutian Islands can be found in between the trench and the continental shelf. These are not to be confused with mid ocean ridges, which are long ridges of mountains created by 2 plates moving apart at a constructive plate margin. Where these mountains rise above the level of the sea Islands such as Iceland are formed.