Archean Earth History

Question 1

why are many Archean rocks difficult to interpret

Answer 1

• many metamorphosed and complexly deformed
• buried beneath younger rocks
• contain few fossils

Question 2

how many continents have a ancient stable Craton

Answer 2

all have them

Question 3

what is a shield

Answer 3

exposed Precambrian rock

Question 4

what is a platform

Answer 4

covered Precambrian rock

Question 5

what are Cratons

Answer 5

Shield and Platforms

Question 6

what are the characteristics of Continental crust

Answer 6

• 35km thick
• granitic composition
  0-4 billion years old

Question 7

what are the characteristics of Oceanic Crust

Answer 7

-7km thick-
- basaltic composition
- less than 180 million years old

Question 8

why did Archean plates moves faster than today

Answer 8

more heat in earth caused faster magma convection

Question 9

what two terranes are Archean rocks divided into

Answer 9

Green stone belts (GSB)
Granit-gneiss complexes (GGC)