Earth & SkyGreek → English
Asthenosphere
/æsˈθɛnəsfɪr/noun
The soft, slowly flowing layer of the upper mantle on which the tectonic plates ride.
The Greek roots
ἀσθενής
asthenḗs
without strength, weak
σφαῖρα
sphaîra
ball, sphere
Literally: “weak sphere”
The story of the word
Joseph Barrell named the layer in 1914, decades before anyone could observe it. He reasoned from the way land rebounds after ice sheets melt that something under the crust has to yield, and called that weak zone the asthenosphere. The rock there is not molten, only close enough to its melting point to creep, which is exactly what lets the plates above it move.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 1914
Same family
astheniamyasthenianeurasthenialithosphereatmosphere
In a sentence
Seismic waves slow down as they cross into the asthenosphere.
Scandinavia is still rising as the asthenosphere flows back under it.