Geology, Plate Tectonics, Earth's structure

Plate tectonics is the unifying theory of modern geology that explains how the Earth's outer shell moves and reshapes itself. The planet is layered: a thin outer crust, a thick rocky mantle, and a metallic core. The crust and the rigid uppermost mantle together form the lithosphere, which is broken into a number of large and small plates. These plates rest on the asthenosphere, a hotter, weaker part of the mantle that can flow slowly over geological time, allowing the plates above to drift.

Continental crust is thicker and less dense than the oceanic crust that floors the deep oceans. New oceanic crust is created at mid-ocean ridges, where plates pull apart and molten rock rises to fill the gap, a process called sea-floor spreading. Elsewhere, plates collide: denser oceanic crust descends, or subducts, beneath another plate and is recycled into the mantle, while continental collisions can crumple the crust into mountain ranges. Along other boundaries plates slide past one another horizontally.

This constant motion accounts for many of the planet's most striking features and hazards. Most earthquakes occur along plate boundaries, where the grinding and locking of plates builds stress that is released in sudden slips. Volcanism is concentrated at spreading ridges and above subduction zones. The same processes drive the long-term drift of continents, the opening and closing of oceans, and the distribution of mountain belts, recorded over hundreds of millions of years in the rocks and the shape of the ocean floor.

Frequently asked questions

What is the difference between the lithosphere and the asthenosphere?: The lithosphere is the rigid outer layer, made of the crust and uppermost mantle, that is broken into plates. The asthenosphere beneath it is hotter and able to flow slowly, allowing those plates to move.
What is sea-floor spreading?: It is the creation of new oceanic crust at mid-ocean ridges, where plates separate and rising magma solidifies. The new crust then moves outward on either side of the ridge.
Why do earthquakes occur mostly at plate boundaries?: Plate boundaries are where plates collide, separate or slide past each other. The stress that builds as plates interact is released as earthquakes, so seismic activity concentrates along these margins.

Geology:
Black smokers	Earthquakes	Geysers	Tsunamis
Caves	Floods	Minerals	Volcanoes
Disasters	General overview	Plate tectonics	Volcano list

Internal structure of the earth

Composition & internal structure of the Earth

Earth-mantle- core physics of the Earth mantle core, dedicated to the Earth’s interior structure and the history of its exploration

Earth's Crust contour map of the thickness of the Earth's crust

Earth's interior the earth is divided into four main layers: the inner core, outer core, mantle, and crust

Earth's structure structure and composition of the Earth

Earth's structure Earth's structure

Earth's structure

Earth's structure ispheres, core, center of the Earth, mantle, outermost layer, crust, volcanic rocks, basalt, silica, granite. lithosphere, asthenosphere

Earth structure

Earth Structure and Rock Cycles

Earth: the inner core internal structure of the Earth

Earthquakes and the Earth's interior

Internal structure of the Earth internal structure of the Earth

Seismology and Earth's interior Body Waves, P Waves, S Waves, Inner Core - Outer Core Boundary, Lithosphere - Asthenosphere Boundary

Structure of the Earth The interior structure of the Earth, similar to the outer, is layered. These layers can be defined by either their chemical or their rheological properties. The Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core

Velocity Structure of the Earth The phenomenon of plate tectonics gives evidence of sources of energy within the Earth. Although the Earth's heat output each day is much smaller than the amount of solar energy it receives, it is enough to build mountains that resist the solar-driven processes of erosion. To understand how plate tectonics works, we must understand the nature of the Earth's interior

Plate tectonics