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Plate Tectonics

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Josh Thomas

on 7 February 2014

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Transcript of Plate Tectonics

Plate Tectonics
7th Grade Science - Thomas
Earth's Interior
Geologist use 2 main types of evidence to learn about Earth's interior.
Journey to the Center of the Earth
Start up your gigantic drill and head to the center of the Earth

You will pass through the
, the
, and then into the

Core and Inner Core
Convection in the Mantle
The inside of the Earth is very hot! What causes something to be hot?
Alfred Wegener
Wegener had an idea about the natural world and made a hypothesis!
Sea Floor Spreading
What is Sea-Floor Spreading?
-Rock Samples from inside Earth
-Ex. Caves
-Seismic Waves and how they travel through the Earth
- strong, solid layer made of the
uppermost mantle
and the
Asthenosphere - section of mantle underneath the lithosphere; this layer is very soft and can bend like plastic due to it's higher temperature........much like peanut butter
As you travel, two things happen
-temperature increase
-pressure increase
End of Section
layer of molten metal
dense ball of solid metal - due to the pressure the atoms can not spread out and become liquid
Three types of Heat Transfer
is the transfer of energy through space with NO direct contact
is heat transfer within a material; or between materials that are touching (have contact)
is heat transfer by the movement of currents within a fluid
End of Section
His hypothesis was that all the continents were once connected into on big land mass called:
Wegener's Hypothesis became known as Continental Drift
Continental Drift - idea that continents slowly move across Earth's Surface
Wegener's hypothesis was supported by evidence:
Land Features
Wegener couldn't explain what caused plates to move so most geologists didn't accept his hypothesis....but he kept looking
What theories have been accepted now about the forces that move Earth's lithospheric plates?
Asthenosphere and Convection Currents
End of Section
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Maybe Wegener isn't so crazy after all!?
The ocean floor provides evidence to support Wegener's theory.
Mid-Ocean Ridges
undersea mountain chain where new ocean floor is produced
Mid-Ocean Ridges were discovered with technology called SONAR.
Sea-Floor Spreading
American Geologist: Harry Hess
Hess hypothesized that: Sea-Floor Spreading continually adds new material to the ocean floor.
At cracks in the oceanic crust, new rock is added when molten material rises and erupts.
Evidence - 3 types
Fluffy rock - Hess found evidence that molten material was erupting due to the shape of rocks on the sea-floor
Magnetic Stripes - when the molten material cooled, the iron bits lined up creating a magnetic memory. This pattern was identical on both sides of the mid-ocean ridge
Drilling - the youngest rock samples were found at the ridge and they gradually got older the farther away they were
Supported by evidence???
old ocean floor plunges into deep-ocean trenches and back into the mantle
Deep-Ocean Trenches
This process is called subduction
If new ocean floor is being made, does the world just keep getting bigger???
Plate Tectonics
This Theory states that pieces of the Earth's lithosphere are in slow, constant motion, driven by convection currents in the mantle.
Wilson, a Canadian scientist, noticed cracks on the continents like the mid-ocean ridges. He combined all the ideas about continental drift, sea-floor spreading, and lithospheric plates into one large theory explaining everything.
Plate Boundaries
A fault is any place where there is a break in the Earth's surface and rocks slip past each other.
In contrast, a plate boundary is where two lithospheric plates meet.
Sooo.... All plate boundaries are faults, but not all faults are plate boundaries.
Divergent Boundaries
where two plates move apart
Rift Valley
a rift valley forms along the divergent boundary
Convergent Boundaries
this is where two plates come together, or converge
Transform Boundaries
where two plates slip past each other in opposite directions
Earthquakes often occur here but crust is neither created nor destroyed
End of Section
Full transcript