Week Twelve Notes-Geology G-104
Week Twelve Notes-Geology G-104 GEOL-104 20584
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This 2 page Class Notes was uploaded by Ashley Hughes on Thursday April 9, 2015. The Class Notes belongs to GEOL-104 20584 at Indiana University taught by Laura Wasylenki in Spring2015. Since its upload, it has received 79 views. For similar materials see Evolution of the Earth in Geology at Indiana University.
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Date Created: 04/09/15
4715 G104 0 Precambrian is everything before fossils visible to the naked eye before 542 million years 0 O Hadean Eon 456 billion years ago to 38 billion years ago I Hades hot Archean Eon 38 billion years ago to 25 billion years ago I Archaic old ancient Proterozoic Eon 25 billion years ago to 542 million years ago I Protero before zoic life 88 of the time but only 20 of all rocks exposed on land are Precambrian and land is only about 13 of earth s surface so 7 of the earth s surface exposes Precambrian rocks No Hadean rocks preserved I Earth had more than 3 times as much heat owing out of the surface in the Hadean I 3060 molten from so many big impacts 0 Allowed core and mantle to separate 0 Likely had a magma ocean and extremely vigorous convection O No crust or continents 0 About 452 billion years ago there was a big crash pieces swept away 0 Made moon 0 Maria basalts filled some big cratersmoon had volcanism core mantle crust 0 Lots of impacts dusty atmosphere made of sulfur dioxide and methane and CO vigorous convection magma ocean thin bits of basaltic crust 0 End marked by oldest rocks we ve found Archean had 23 times as much heat ow as now transition to what is today I Not big pieces of land not stable I Protocontinents and greenstones I Small pieces of crust are sutured together With folded lowgrade metamorphic rock 0 Don t last more dense I Banded iron formations 0 Marine sediments formed 3818 billion years ago mostly 3525 billion years ago 0 Rich in reduced Fe and silica 0 Reduced Fe only possible With low oxygen 0 They tell us there were standing bodies of water as early as 38 billion years ago I First real continent and stratigraphic section I Still fast convection lots of volcanism only tiny bits of land little clastic sediment atmosphere rich in methane ammonia water and C02
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