Transcript formation_of_crust

Formation of Crust &
Continents
• Due to intense heat, scientists believe the
Earth consisted of hot molten magma. As
Earth cooled minerals and elements
became concentrated in specific zones
Differentiation
• Process by which the planet becomes
internally zoned when heavy materials
sink toward its center and lighter material
near its surface
– Layers of the Earth,
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Crust
Mantle
Outer core
Inner core
Earliest Crust
• Early crust formed as soon as the upper
layer cooled.
• Crust was similar to basaltic crust that
underlies Earth’s oceans.
Continental Crust
• As crust was recycled and returned to the
mantle it carried water.
• As materials returned back to the crust, it
crystallized to form small fragments of
granite, which make up much of today’s
Earth crust
Continental Crust
• As volcanoes erupted during the Archean
era.
• Small fragments of granite known as
microcontinents continued to form
Cratons
• Most
microcontinents
still exists as the
cores of todays
continents.
• A craton is the
oldest and most
stable part of a
continent
Precambrian Shields
• Most cratons are burried beneath
sedimentary rocks, in some places erosion
has exposed these rocks. These exposed
rocks are known as precambrian shields
Laurentia
• Earth’s largest Proterozic landmass
• Ancient continent of North America
1st Supercontinent
• Collision of Laurentia with Amazonia
occurred 1.3 – 1 bya at the end of the
Proterozic era
• Formed Earth's 1st supercontinent, called
Rodinia
• Pangea formed 200 mya