Worlds of David Darling
Encyclopedia of Science
   
Home > Encyclopedia of Science

Acasta formation




Acasta gneiss
Orthogneisses, about 4 billion years old, with older enclaves of mafic rock, Slave Craton, Canada. Credit: Yuichiro Ueno, Tokyo Institute of Technology
The oldest known outcrop of rock on Earth. It occurs about 350 km north of Yellowknife in Canada's Northwest Territories and consists of gneiss (a type of coarse-grained metamorphic rock) that dates back just under four billion years – to around the beginning of the period of late heavy bombardment.


Related category

   • GEOLOGY AND PLANETARY SCIENCE