Lithosphere
/ˈlɪθəsfɪər/noun
The rigid outer shell of the Earth, made of the crust and the uppermost mantle, broken into the tectonic plates.
The Greek roots
Literally: “stone sphere”
The story of the word
Nineteenth-century geology used the word loosely for the stony part of the planet, alongside atmosphere and hydrosphere. Joseph Barrell gave it the modern meaning in 1914 by pairing it with a new word, asthenosphere, the weak sphere beneath, arguing that a strong layer must be floating on something that flows. Plate tectonics half a century later was built on exactly that division, so the plates are lithosphere and what they slide over is the weak layer Barrell named.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 19th century
Same family
In a sentence
Oceanic lithosphere gets colder, denser and thicker as it moves away from the ridge.
The plates are lithosphere, not crust, which is a distinction first-year students always have to unlearn.