asthenosphere

American  

[as-then-uh-sfeer] / æsˈθɛn əˌsfɪər /

noun

Geology.

1. the region below the lithosphere, variously estimated as being from fifty to several hundred miles (eighty-five to several hundred kilometers) thick, in which the rock is less rigid than that above and below but rigid enough to transmit transverse seismic waves.

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asthenosphere British  

/ əsˈθiːnəˌsfɪə, -ˈθɛn- /

noun

1. a thin semifluid layer of the earth (100–200 km thick), below the outer rigid lithosphere, forming part of the mantle and thought to be able to flow vertically and horizontally, enabling sections of lithosphere to subside, rise, and undergo lateral movement See also isostasy

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asthenosphere Scientific  

/ ăs-thĕn′ə-sfîr′ /

1. The upper part of the Earth's mantle, extending from a depth of about 75 km (46.5 mi) to about 200 km (124 mi). The asthenosphere lies beneath the lithosphere and consists of partially molten rock. Seismic waves passing through this layer are significantly slowed. Isostatic adjustments (the depression or uplift of continents by buoyancy) take place in the asthenosphere, and magma is believed to be generated there.

2. Compare atmosphere hydrosphere lithosphere

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Etymology

Origin of asthenosphere

First recorded in 1910–15; from Greek asthen(ḗs) “frail, weak, sickly” + -o- + -sphere; see asthenia

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Compare meaning

How does asthenosphere compare to similar and commonly confused words? Explore the most common comparisons:

• lithosphere vs. asthenosphere

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Example Sentences

See Examples For:

asthenosphere

Beneath it lies the asthenosphere, a hotter and more ductile layer that slowly flows over geologic time.

From Science Daily ● Jun. 28, 2026

This difference in water content between the two layers constituting the LAB can explain the sharp velocity drops as well as the near constant attenuation observed over a wide frequency range in the asthenosphere.

From Science Daily ● Sep. 27, 2023

This layer appears to glide over a weaker region below called the asthenosphere, characterized by high seismic attenuation and low shear wave velocity.

From Science Daily ● Sep. 27, 2023

Physical layers include lithosphere and asthenosphere; chemical layers are crust, mantle, and core.

From Textbooks ● Jan. 1, 2017

So all that can be said is that at some slightly indeterminate point as we head toward the center of Earth we leave the asthenosphere and plunge into pure mantle.

From "A Short History of Nearly Everything" by Bill Bryson

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