The lithosphere is the solid, outer part of the Earth. The lithosphere includes the brittle upper portion of the mantle and the crust, the outermost layers of Earth's structure. It is bounded by the atmosphere above and the asthenosphere (another part of the upper mantle) below.

Although the rocks of the lithosphere are still considered elastic, they are not viscous. The asthenosphereis viscous, and the lithosphere-asthenosphere boundary (LAB) is the point where geologists and rheologists—scientists who study the flow of matter—mark the difference in ductility between the two layers of the upper mantle. Ductility measures a solid material's ability to deform or stretch under stress. The lithosphere is far less ductile than the asthenosphere.

There are two types of lithosphere: oceanic lithosphere and continental lithosphere. Oceanic lithosphere is associated with oceanic crust, and is slightly denser than continental lithosphere.

Plate Tectonics

The most well-known feature associated with Earth's lithosphere is tectonic activity. Tectonic activity describes the interaction of the huge slabs of lithosphere called tectonic plates.

The lithosphere is divided into tectonic plates including the North American, Caribbean, South American, Scotia, Antarctic, Eurasian, Arabian, African, Indian, Philippine, Australian, Pacific, Juan de Fuca, Cocos, and Nazca.

Most tectonic activity takes place at the boundaries of these plates, where they may collide, tear apart, or slide against each other. The movement of tectonic plates is made possible by thermal energy (heat) from the mantle part of the lithosphere. Thermal energy makes the rocks of the lithosphere more elastic.

Tectonic activity is responsible for some of Earth's most dramatic geologic events: earthquakes, volcanoes, orogeny (mountain-building), and deep ocean trenches can all be formed by tectonic activity in the lithosphere.

Tectonic activity can shape the lithosphere itself: Both oceanic and continental lithospheres are thinnest at rift valleys and ocean ridges, where tectonic plates are shifting apart from one another.

How the Lithosphere Interacts with Other Spheres

The cool, brittle lithosphere is just one of five great "spheres" that shape the environment of Earth. The other spheres are the biosphere (Earth's living things); the cryosphere (Earth's frozen regions, including both ice and frozen soil); the hydrosphere (Earth's liquid water); and the atmosphere (the air surrounding our planet). These spheres interact to influence such diverse elements as ocean salinity, biodiversity, and landscape.

For instance, the pedosphere is part of the lithosphere made of soil and dirt. The pedosphere is created by the interaction of the lithosphere, atmosphere, cryosphere, hydrosphere, and biosphere. Enormous, hard rocks of the lithosphere may be ground down to powder by the powerful movement of a glacier (cyrosphere). Weathering and erosion caused by wind (atmosphere) or rain (hydrosphere) may also wear down rocks in the lithosphere. The organic components of the biosphere, including plant and animal remains, mix with these eroded rocks to create fertile soil—the pedosphere.

The lithosphere also interacts with the atmosphere, hydrosphere, and cryosphere to influence temperature differences on Earth. Tall mountains, for example, often have dramatically lower temperatures than valleys or hills. The mountain range of the lithosphere is interacting with the lower air pressure of the atmosphere and the snowy precipitation of the hydrosphere to create a cool or even icy climate zone. A region's climate zone, in turn, influences adaptations necessary for organisms of the region's biosphere.

lithosphere

The rocky lithosphere includes part of the upper mantle and crust.

Extraterrestrial Lithospheres
All terrestrial planets have lithospheres. The lithospheres of Mercury, Venus, and Mars are much thicker and more rigid than Earth's.

The LAB

The depth of the lithosphere-asthenosphere boundary (LAB) is a hot topic among geologists and rheologists. These scientists study the upper mantle's viscosity, temperature, and grain size of its rocks and minerals. What they have found varies widely, from a thinner, crust-deep boundary at ocean ridges to thick, 200-kilometer (124-mile) boundary beneath cratons, the oldest and most stable parts of continental lithosphere.

Noun

a modification of an organism or its parts that makes it more fit for existence. An adaptation is passed from generation to generation.

air pressure

Noun

force pressed on an object by air or atmosphere.

asthenosphere

Noun

layer in Earth's mantle between the lithosphere (above) and the upper mantle (below).

Noun

layers of gases surrounding a planet or other celestial body.

Noun

all the different kinds of living organisms within a given area.

Noun

part of the Earth where life exists.

brittle

Adjective

fragile or easily broken.

climate zone

Noun

area separated from others by its long-term weather patterns.

continental crust

Noun

thick layer of Earth that sits beneath continents.

convection

Noun

transfer of heat by the movement of the heated parts of a liquid or gas.

Noun

rocky outermost layer of Earth or other planet.

cryosphere

Noun

icy part of the Earth's waterincluding icebergs, glaciers, and ice caps.

dense

Adjective

having parts or molecules that are packed closely together.

diverse

Adjective

varied or having many different types.

ductility

Noun

ability of a solid material to withstand stress or force by changing form instead of breaking.

Noun

our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

earthquake

Noun

the sudden shaking of Earth's crust caused by the release of energy along fault lines or from volcanic activity.

elastic

Adjective

able to bend easily.

environment

Noun

conditions that surround and influence an organism or community.

Noun

act in which earth is worn away, often by water, wind, or ice.

fertile

Adjective

able to produce crops or sustain agriculture.

geologic

Adjective

having to do with the physical formations of the Earth.

geologist

Noun

person who studies the physical formations of the Earth.

Noun

mass of ice that moves slowly over land.

Noun

land that rises above its surroundings and has a rounded summit, usually less than 300 meters (1,000 feet).

Noun

all the Earth's water in the ground, on the surface, and in the air.

Noun

the geographic features of a region.

Noun

outer, solid portion of the Earth. Also called the geosphere.

lithosphere-asthenosphere boundary (LAB)

Noun

chemical and mechanical distinction between the cool, rigid lithosphere and the warmer, more ductile asthenosphere.

Noun

middle layer of the Earth, made of mostly solid rock.

mid-ocean ridge

Noun

underwater mountain range.

mountain

Noun

landmass that forms as tectonic plates interact with each other.

oceanic crust

Noun

thin layer of the Earth that sits beneath ocean basins.

Noun

a long, deep depression in the ocean floor.

organic

Adjective

composed of living or once-living material.

orogeny

Noun

the way mountains are formed.

pedosphere

Noun

layer of Earth consisting of soil and all it contains (such as water, air, organisms).

plastic

Noun

chemical material that can be easily shaped when heated to a high temperature.

Noun

all forms in which water falls to Earth from the atmosphere.

Noun

all forms in which water falls to Earth from the atmosphere.

Noun

liquid precipitation.

remains

Noun

materials left from a dead or absent organism.

rheologist

Noun

scientist who studies the flow and shape-changing (deformation) of matter.

Noun

depression in the ground caused by the Earth's crust spreading apart.

rock

Noun

natural substance composed of solid mineral matter.

snow

Noun

precipitation made of ice crystals.

soil

Noun

top layer of the Earth's surface where plants can grow.

stress

Verb

to strain or put pressure on.

tectonic activity

Noun

movement of tectonic plates resulting in geologic activity such as volcanic eruptions and earthquakes.

tectonic plate

Noun

massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate.

Noun

degree of hotness or coldness measured by a thermometer with a numerical scale.

thermal energy

Noun

heat, measured in joules or calories.

valley

Noun

depression in the Earth between hills.

viscous

Adjective

liquid that is thick and sticky.

Noun

an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

Noun

the breaking down or dissolving of the Earth's surface rocks and minerals.

Noun

movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

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    Editor

    Jeannie Evers, Emdash Editing

    Producer

    Caryl-Sue, National Geographic Society

    Last Updated

    May 20, 2015

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