GEO 103 Lecture 15: Hadeon Eon
Document Summary
Basalt (dark) and granite (light) - n. ontario. Canadian shield and adjacent platform made up of numerous units or smaller archean cratons. Cratons amalgamated during late archean and early proterozoic. Absolute ages and structural trends help geologists identify various smaller cratons. Drilling and geophysical evidence indicate precambrian rocks underlie much of north americap. In places exposed by deep erosion or uplift. No rocks of hadean age are present on earth. Hadean-aged rocks are present and can be studied on moon and mars. Differentiated into core, mantle and some type of crust. High internal heat due to energy of accretion and high radioactivity. Giant impact to form moon (~4. 5 gyr) likely resulted in melting of earth. After magma ocean cools, surface highly disrupted by massive meteorite impacts. On earth, > 200 basins > 1,000 km between 4. 1-3. 8 gyr. Ratio of radiogenic heat production in past compared to present.
