earth’s interior and pt notes
TRANSCRIPT
Earth’s Interior
• Geologists have only been able to drill to 3.8 kilometers.• The center of the Earth is more than 6,000 kilometers deep.Since Geologists cannot observe the Earth’s interior directly, they must rely on indirect measures.• Seismic Waves are recorded and study how they travel through the medium of the Earth.•This information has shown that the Earth has several layers.
Crust
Crust: the layer of rock that forms Earth’s outer skin.• The crust includes rocks, mountains, soil, and water.• The outer rind of rock is much thinner than what is
beneath it.
• The crust includes both dry land and the ocean floor.• It is thinnest beneath the ocean and thickest under
mountains.•The crust can range from 5-40 kilometers.•Oceanic crust is made up of basalt.•Continental crust is made up of granite.
Mantle
The mantle is a layer of hot rock that extends nearly 3,000 kilometers deep.
• The Lithosphere is the upper portion of the mantle and the lower portion of the crust.
• It is approximately 100 kilometers deep and floats on top of the Asthenosphere .
•The Asthenosphere is a soft layer of the mantle.
•This layer flows slowly.
•The Asthenosphere is approximately 350 kilometers deep.
•The Mesosphere is the solid lower part of the mantle below the Asthenosphere .
Earth’s Magnetic Field
• Currents in the liquid outer core force the solid inner core to spin. (planet within another)•The inner core spins slightly faster than the rest of the planet.•This movement creates the Earth’s magnetic field.
Earth’s Interior
The theory that states that pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents
in the mantle.
• The theory of plate tectonics
explains the formation,
movement, and subduction of Earth’s plates.
Forces that causes Earth’s plates to move.
• The plates of the lithosphere float on top of the Asthenosphere.
• Convection currents rise in the Asthenosphere and spread out beneath the lithosphere.
• Convection current forces drag the overlying plates along. The currents cool and sink deeper into the mantle.
• Scientists think that the downward movement may provide the force that causes the subduction of plates carrying oceanic crust.
Forces that causes Earth’s plates to move.
Slab Push Hypothesis
• Magma rising along the mid oceanic ridge exerts a force that pushes an oceanic plate away from the ridge.
• The force of gravity causes plate movement by pulling cooler, denser oceanic plates down toward the mantle.
• Slab push and pull work together with convection currents to move the plates.
The earth’s surface is made up of about nine large plates and several
smaller plates.
Places where two plates meet.
There are three types of plate boundaries.
1. Transform Boundary
2. Divergent Boundary
3. Convergent Boundary
Two plates slip past each other, moving in opposite
directions.
Earthquakes occur frequently along this boundary.
The San Andreas Fault in
California is an example
of a transform
fault along a transform boundary.
Two plates move away from each other.
• When divergent boundaries develop on land, two of Earth’s plates slide apart.
• A rift valley forms along the divergent valley.
• Ex. The Great Rift Valley in east Africa is about 3,000 kilometers long.
Divergent Boundary
Two plates move towards each other.
• When plates converge, it results in a collision.
• Collisions happen between:
1. Oceanic crust to oceanic crust
2. Oceanic crust to continental crust
3. Continental crust to continental crust
Plate Movement
• The plates move at about 1-10 centimeters per year.
• The North American and Eurasian plates move at about 2.5 cm/year.
Plate Movement
• Pangaea existed about 260 million years ago.
• Approximately 225 million years ago Pangaea began to break apart.
