"Plate tectonics is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago."
The relationship between plate tectonics, volcanoes, and earthquakes and their distribution around the world.
Plate tectonics: The theory that Earth's outer shell is divided into several plates that float on the underlying mantle and interact with one another.
Types of plate boundaries: Divergent, convergent, and transform.
Magma and lava: Molten rock beneath the earth's surface and when it erupts on the surface.
Types of volcanoes: Shield, cinder cone, composite/stratovolcano, and lava dome.
Volcanic hazards: Ash, lava flows, lahars, pyroclastic flows, and toxic gases.
Types of earthquakes: Tectonic, volcanic, and human-induced.
Earthquake hazards: Shaking, liquefaction, landslides, and tsunamis.
Seismic waves: Waves of energy that are generated by an earthquake.
Seismology: The study of earthquakes and seismic waves.
Plate movement: How and why plates move, along with plate motion visualization tools.
History of major earthquakes and volcanic eruptions: The impact and related geologic events caused by earthquakes and volcanic eruptions throughout history.
Plate tectonics and the Earth's interior: The relationship between plate motion and the Earth's mantle and core.
The Ring of Fire: A major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur.
Plate boundaries and their features: Rift valleys, geysers, hot springs, and ocean trenches.
Plate tectonics and global impacts: Climate change, sea level rise, and ecosystem changes.
Shield Volcanoes: These are low-profile volcanoes that form from the accumulation of fluid lava flows. The lava flows out from a central vent and spreads out, forming a broad, slightly domed shape.
Composite Volcanoes: These are tall and steep-sided mountains that are formed from a mixture of lava flows, ash, and other volcanic materials. They have a characteristic cone shape and can produce explosive eruptions.
Cinder Cone Volcanoes: These are small, steep volcanoes that consist of loose volcanic ash and rock fragments. They are formed by eruptions that are more explosive than those of shield volcanoes.
Lava Domes: These are formed by viscous (thick) lava that piles up around a volcano's vent. They can be formed by eruptions that are explosive or non-explosive.
Strike-Slip Faults: These are caused by the side-to-side movement of two blocks of rock along a fault plane. The San Andreas fault in California is an example of a strike-slip fault.
Reverse Faults: These are caused by the compression of two blocks of rock, which causes one block to be pushed up and over the other block. The Himalayan Mountains were formed by the collision of the Indian and Eurasian Plates, which caused significant reverse faulting.
Normal Faults: These are caused by the tensional forces that pull apart two blocks of rock along a fault plane. The Rio Grande Rift in New Mexico is an example of a normal fault.
Megathrust Earthquakes: These occur in subduction zones where one tectonic plate is forced under another. These earthquakes can be very powerful and can cause significant damage, as seen in the 2004 Indian Ocean earthquake and the 2011 Tohoku earthquake and tsunami.
"The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century."
"Plate tectonics came to be accepted by geoscientists after seafloor spreading was validated in the mid-to-late 1960s."
"Earth's lithosphere is broken into seven or eight major plates."
"Where the plates meet, their relative motion determines the type of plate boundary: convergent, divergent, or transform."
"Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries."
"The relative movement of the plates typically ranges from zero to 10 cm annually."
"Tectonic plates are composed of the oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust."
"Along convergent plate boundaries, the process of subduction, or of one plate moving under another, carries the edge of one plate down under the other plate and into the mantle."
"The lost surface is balanced by the formation of new oceanic crust along divergent margins by seafloor spreading."
"This process of plate tectonics is also referred to as the conveyor belt principle."
"Tectonic plates are able to move because Earth's lithosphere has greater mechanical strength than the underlying asthenosphere."
"Plate movement is driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography and density changes in the crust."
"At subduction zones, the relatively cold, dense oceanic crust sinks down into the mantle forming the downward convecting limb of a mantle cell. This is the strongest driver of the plates."
"The relative importance of other proposed factors such as active convection, upwelling and flow inside the mantle, and tidal drag of the moon, and their relationship to each other is still the subject of debate."