Orogeny the Ways that Mountains Form

The ways that mountains form is the geologic process called orogeny. . Different types of rock determine how high the rocks will rise. Two main branches of science concerned with orogeny are geology and geochronology. The movement of tectonic plates through earthquakes and volcanoes accelerate the process forming orogenic belts. By looking at the Earth’s crust, geologists understand how mountains form.

Mountains form from four structural zones. Each of the zones uses a special type of formation. Patterns of layering, sedimentary breakage, seismic and volcanic activity, and ocean trenches all help to explain the world of mountain formation. They have four lithologic zones and three metamorphic zones.

In the metamorphic zones, Greenschist-Amphibolite Metamorphism occurs in any of the zones. It uses high temperatures that reduce the mica to feldspar to amphibole to pyroxene. Blueschist uses high pressure and low temperature to give the rocks a bluish color. Eclogite Metamorphism, at 100 kilometers, produces garnets and light green pyroxenes. This happens in shallow waters at cooler temperatures. This process pulls the slab of rock downward creating movement along the tectonic plates.

The Craton zone covers the middle part of the continent. It contains very old exposed rock called shields, but movement is minimal here. Lithologically, this is the platform as it has a thin mantle of sedimentary rocks.

The Accretionary Prism zone is a stronghold in which layers of earth stack up against it much like a bulldozer does. It creates an immoveable wedge. These layers contain rocks from deep down. They are very thick.

The Igneous Arc is a melting zone 100 kilometers deep within the crust that forms volcanoes. This is opposite the accretionary prism because it weakens the rocks around it so that they crumble and crack. It is the most destructive zone. Its layers like the accretionary prism also are very thick.

The Foreland is a zone in which the rocks fold up much the way carpeting does when furniture pushes against it. Identified by its reddish color, it is also a mild form of deformation. The layers of shale, salt, and gypsum make up the zone.

Orogeny builds a mountain to a specific height by shortening and thickening the crust. Here also isostasy comes into play as it makes the mountain rise to its altitude.

Geochronology works with dating the events that the above process records. By determining which zones the rocks are in, scientists can determine the approximate age of the studied areas.