GEOL 122 Chapter Notes - Chapter 11: Canadian Shield, Redshift, Archean
Document Summary
*most geological information about the precambrian is derived from cratons, the large portions of continents that have not undergone substantial tectonic deformation since early paleozoic time. Precambrian shield- large precambrian portion of a craton that is exposed at earth"s surface. Redshift- increase in the wavelength of lightwaves travelling through space, evidence that the universe is expanding. Supernova- exploding star that casts off matter of low density. Protocontinents- numerous felsic bodies of rock that emerged during archean time formed small continents. Terrane- is a geologically distinctive region of earth"s crust that has behaved as a coherent crustal block. Greenstone belts- long stratified rock bodies that sit in masses of high grade metamorphic rocks of felsic composition (gneisses). *life appeared on earth after 4. 5 billion years ago. Mantle differentiated enough to form small cratons (continental crust) Oceans formed due to volcanic emission of water vapour which condensed. Dissolved salts from weathering of exposed rocks and ocean crust.
