Dynamic Planet/Tectonics

Tectonics is the topic of Dynamic Planet for the 2017 season.

General Plate Tectonics
Tectonic plates are the pieces of the Earth's crust that "float" on the asthenosphere and make up the lithosphere. They are driven by convection currents in the mantle caused by the heat of the core due to pressure. There are two types of plates: oceanic and continental plates. Continental plates are thicker than oceanic plates, but oceanic plates are denser than continental plates. Oceanic plates are made of denser rocks due to cooling quickly and having fine-crystals.

History of Plate Tectonics Theory
In 1912, Alfred Wegener composed the theory of Plate Tectonics. The idea of a supercontinent was derived from inspecting fossil patterns and crust thickness.

Plate Boundaries
Plate boundaries are where the different pieces of the crust, known as tectonic plates, meet.

Convergent
When two plates collide with each other or come together, the boundary between the two plates is known as a convergent boundary.

Oceanic-Oceanic

When two oceanic plates converge, it causes subduction and creates a trench. The trench is the deepest part of the ocean because one plate is actually going underneath the other. Oceanic-oceanic convergent boundaries are also responsible for hotspots as magma from the mantle gets trapped between the two plates and is forced upwards.

Oceanic-Continental or Continental-Oceanic

When a continental and an oceanic plate converge, the oceanic plate always subducts underneath the continental. These boundaries create volcanoes and active margins and trenches, but the trenches are not as deep.

Continental-Continental

When two continental plates converge, the plate is pushed upwards creating mountains.

Tectonic Hazards
For more detailed information, see the Earthquakes and Volcanoes page

Links
USGS Plate tectonics Publication