as·​theno·​sphere as-ˈthe-nə-ˌsfir How to pronounce asthenosphere (audio)
: a zone of a celestial body (such as the earth) which lies beneath the lithosphere and within which the material is believed to yield readily to persistent stresses
asthenospheric adjective

Example Sentences

Recent Examples on the Web Schematic model for a partially molten layer in the asthenosphere. Erik Klemetti, Discover Magazine, 20 Feb. 2023 This layer is a part of the asthenosphere, which sits beneath the tectonic plates. Ashley Strickland, CNN, 7 Feb. 2023 Beneath that, starting at roughly 100 kilometers deep, is the asthenosphere, where mantle rocks are warm enough to flow like hot taffy. Alexandra Witze, Discover Magazine, 30 July 2018 Cold, dense oceanic lithosphere sinks below an adjacent, lighter plate, plunging into the hot asthenosphere. National Geographic, 13 Jan. 2023 Magma can then be generated by decompression melting as the asthenosphere ascends to fill in the space of the detached lithosphere. Erik Klemetti, Discover Magazine, 21 July 2011 When the eclogite anchor drops off, that detachment may cause hot rocks from the asthenosphere to well upward in the region, allowing the crustal flow to get going and the molasses to begin flowing. Alexandra Witze, Discover Magazine, 30 July 2018 Roughly 90 percent of quakes on Earth are produced by the movement of tectonic plates, massive slabs of the planet’s lithosphere that slide around atop the semisolid asthenosphere layer and occasionally bump into one another. Joanna Thompson, Scientific American, 24 May 2022 These pieces, divided between older continental crust and younger oceanic crust, ride atop the gooey asthenosphere, a semiliquid layer of magma and partly melted rock. Gemma Tarlach, Discover Magazine, 12 June 2019 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'asthenosphere.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


Greek asthenḗs "weak" + -o- + -sphere — more at asthenia

Note: The term was introduced by the American geologist Joseph Barrell (1869-1919) in "The strength of the earth's crust. Part VI. Relations of isostatic movements to a sphere of weakness—the asthenosphere," Journal of Geology, vol. 22 (1914), p. 659: "The theory of isostasy shows that below the lithosphere there exists in contradistinction a thick earth-shell marked by a capacity to yield readily to long-enduring strains of limited magnitude …To give proper emphasis and avoid the repetition of descriptive clauses it needs a distinctive name. It may be the generating zone of the pyrosphere; it may be a sphere of unstable state, but this to a large extent is hypothesis and the reason for choosing a name rests upon the definite part it seems to play in crustal dynamics. Its comparative weakness is in that connection its distinctive feature. It may then be called the sphere of weakness—the asthenosphere…"

First Known Use

1914, in the meaning defined above

Time Traveler
The first known use of asthenosphere was in 1914

Dictionary Entries Near asthenosphere

Cite this Entry

“Asthenosphere.” Dictionary, Merriam-Webster, Accessed 31 Mar. 2023.

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