allochthon & autochthon
Jan. 2nd, 2025 07:45 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
prettygoodwordallochthon (uh-LOK-thuhn) - (geol.) n., a geological formation not formed where it is but rather moved to its present location by tectonic forces.
autochthon (aw-TOK-thuhn) - (geol.) n., a geological formation in the place of its original formation.
That latter word also has a more common meaning of a person/people who is/are indigenous to a place, which was the original meaning of autókhthōn in Ancient Greek (from autós, self + khthṓn, place). In English, the adjectival form autochthonous was coined around 1800, and then around 1910 geologists coined the contrasting adjective allochthonous (using the prefix allo- derived from Ancient Greek állos, other), using both adjectives for formations. Finally, allochthon was backformed (on the model of autochthon) around 1940.
Oh, and an example of a process that creates an allochthon is low-angle thrust faulting, in which a chunk of earth is pushed on top of a chunk from another plate, and then partially weathered away, exposing both formation.
---L.
autochthon (aw-TOK-thuhn) - (geol.) n., a geological formation in the place of its original formation.
That latter word also has a more common meaning of a person/people who is/are indigenous to a place, which was the original meaning of autókhthōn in Ancient Greek (from autós, self + khthṓn, place). In English, the adjectival form autochthonous was coined around 1800, and then around 1910 geologists coined the contrasting adjective allochthonous (using the prefix allo- derived from Ancient Greek állos, other), using both adjectives for formations. Finally, allochthon was backformed (on the model of autochthon) around 1940.
Oh, and an example of a process that creates an allochthon is low-angle thrust faulting, in which a chunk of earth is pushed on top of a chunk from another plate, and then partially weathered away, exposing both formation.
---L.
