Plate Tectonic Notes

• Earth’s Layers: • Crust • Mantle • Core

Earth’s Layers • Crust Lithosphere outermost layer that is the tectonic plates but does have some mantle rock

• Mantle – 2 Parts Asthenosphere: (solid, soft layer that moves slowly) The layer that the tectonic plates move on Mesosphere: solid lower part of the mantle

• Core – Outer core (liquid iron and nickel) – Inner core (solid iron and nickel)

Earth’s plates

Pangaea- Supercontinent that once existed on Earth around 245 million years ago…

Plate Movement • Continental Drift – Lithosphere (tectonic plates) is divided into plates that slide around on top of the slowly moving asthenosphere – It occurred after the break-up of Pangaea, and since then the continents have drifted apart

Theory of Continental Drift – Alfred Wegener (early 1900’s) was the first to discuss the theory of Pangaea and continental drift. – Theory of Pangaea- claimed that the continents had formed a single land mass which has split apart over time. – Wegner was not the first to suggest this theory, but he was the first to present information from several fields. – Continental Drift Theory – Was that all of the continents were once joined together, but over time have drifted apart., – Pangea – name of the supercontinent that contained all land on Earth

Evidence of Continental Drift

• Evidence of Wegner’s theory: – Similar glacier deposits in South America and Africa, and fossil findings – The outlines of the continents fit with each other. – Mountain ranges line up between Africa and South America.

How does continental drift work? - Plates compress or pull apart from each other

• Plates collide = convergent boundary • Plates separate = divergent boundary • Plates slide past one another horizontally = transform boundary • Subduction zone = one plate slides under another

Convergent Boundary • Plates collide while moving towards each other • When both plates are continental plates, the plates push against each other, creating mountain ranges.

Subduction Zone • When an oceanic plate slides under a continental plate.

Cause: oceanic trenches, and can cause volcanoes to form due to the oceanic plate melting and creating pressure under the continental plate.

Divergent Boundary • Plates separate (pull apart)

When plates pull away from one another they form: sea floor spreading, mid-oceanic ridges or rift valleys

Sea Floor Spreading Theory • Harry Hess formulated the idea of sea floor spreading in 1962. • Sea Floor Spreading Theory- idea that the seafloor moves and carries the continents with it. • Caused by divergent boundaries moving apart and allowing the liquid like asthenosphere to move upward and cool creating new oceanic crust.

Transform Boundary

• Plates slide past one another horizontally • These areas are likely to cause earthquakes, and volcanic action, and fault lines.

What is the force moving Plate tectonics: CONVECTION CURRENTS

- Convection currents in the mantle are what causes the movement of tectonic plates.

- As the extremely hot molten material from the mantle rises toward the crust, it cools enough to become denser and sink back into the hotter area of the mantle.

- The process repeats (cycles) continually.

Rock does two things when stress is placed on it. It can fold or fault (break). When plates push against one another, they form MOUNTAINS.

• Folded Mountains – made when rock is squeezed together and pushed upward

Fault – broken rock layers resulting from stress

• These mainly occur around transform boundaries • They are due to stress from tectonic plate movement.

Ring Of Fire

• 90% of the world's earthquakes and 89% of the world's largest earthquakes occur along the Ring of Fire in the Pacific Ocean from California around to India – Caused by subduction zones.