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EARTH SCIENCE
Movement of the Earth’s Crust
The Earth’s Layers
• The Earth is made up of three layers:
• At the center is the core. The core is solid iron
and nickel. The core is about 3,500 kilometers
thick.
• Outside the core is the mantle. Made of liquid
and solid rocks that churn. The entire mantle is
about 2,900 kilometers thick.
• The outermost layer is the crust. Very thin and
cold, 8-70 kilometers thick. The continents and
oceans floor are part of the crust.
Earth’s Layers
Continental Drift
• According to this theory, the Earth’s
continents used to be joined as a single
large landmass called Pangaea.
Evidence of Pangaea
• Besides the puzzle fit of the continents:
1. Fossils found on one continent were
similar to fossils found on another
continent.
2. Mountain layers seem to continue from
one continent to another.
3. Glacier deposits were found at the
equator where glaciers can not exist.
Sea Floor Spreading
• This theory states that hot magma from
the mantle rises and pours out onto the
ocean floor through cracks in a rift. The
magma hardens cools and forms new
crust.
• This process continues, stretching the
ocean floor and pushes the continents
apart.
• Atlantic Ocean grows 2 ½ inches per year.
Plate Tectonics
• This theory states
that the Earth’s
crust is made of
large sections, or
plates.
Plate Tectonics
•
1.
2.
3.
•
Plates move in three different ways:
Move apart
Collide
Slide into each other
These actions cause Earthquakes and
volcanoes.