Plate tectonics

Plate Tectonics is a scientific theory describing the large-scale motion of seven large plates and the movements of a larger number of smaller plates of the Earth's lithosphere, since tectonic processes began on Earth between 3.3 and 3.5 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s and early 1960s.

History

The concept of plate tectonics has its roots in the continental drift theory, proposed by Alfred Wegener in the early 20th century. However, it was not until the 1960s that the theory was widely accepted, following the discovery of seafloor spreading and the development of paleomagnetism.

Mechanism

The lithosphere, which is the rigid outermost shell of a planet, is broken up into tectonic plates. On Earth, there are seven or eight major plates (depending on how they are defined) and many minor plates. Where plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries (or faults).

Plate Boundaries

Convergent Boundaries

At convergent boundaries, plates collide with each other. This can lead to the formation of mountain ranges, such as the Himalayas, or deep oceanic trenches, like the Mariana Trench.

Divergent Boundaries

At divergent boundaries, plates move apart from each other. This can lead to the creation of new crust, such as at the Mid-Atlantic Ridge.

Transform Boundaries

At transform boundaries, plates slide past each other. This can lead to intense seismic activity, such as the San Andreas Fault in California.

Impact on Earth's Geography

Plate tectonics has played a key role in shaping the Earth's geography. It has led to the formation of continents, oceans, and various landforms. It also influences patterns of volcanism, earthquakes, and mountain building.

See Also

• Continental drift
• Seafloor spreading
• Earthquake
• Volcano