Plate Tectonics

Will California really ever fall off into the ocean?

You should be able to answer this question by the end of the power-point.

Continental Drift• Developed in 1912 by Alfred

Wegner, a German meteorologist.

• Continental Drift proposed that Earth’s continents had once been joined as a single landmass that broke apart and sent the continents adrift.

• Wegner called the supercontinent Pangaea which means “all the earth” in Greek.

• Pangaea broke up 200 mya.

• The northern half of Pangaea was referred to as Laurasia and the southern portion is known as Gondwanaland.

Evidence from rock layers

• When examining the rock layers of where the continents were connected during Pangaea, it was discovered that the rocks were of the same TYPE and AGE!

Fossil Evidence

•Wegner found similar fossils of several different animals and plants that once lived on or near land had been found on widely separated continent.

• The dinosaurs found could NOT swim across oceans, therefore continents had to be connected!

The Continents fit together like puzzle pieces:

Climatic Evidence:•Coal deposits, made accumulation of swamp plants, were found on Antarctica.

•Glacier deposits were found on Africa, India, South America and Australia.

•For example, the Glossopteris was a fern-like shrub and was found in South America, Antarctica and India.

•This plant grew in Temperate Climates, which were places closer to the equator.

Seafloor Spreading• Sea-floor spreading is the

process in which the ocean floor is extended when two plates move apart.

•  As the plates move apart, the rocks break and form a crack between the plates. 

• Earthquakes occur along the plate boundary. 

• Magma rises through the cracks and seeps out onto the ocean floor like a long, thin, undersea volcano or magma slowly come up and cools forming NEW OCEAN FLOOR!

Paleomagnetism• Paleomagnetism is the study

of the record of the Earth’s magnetic poles preserved in various magnetic minerals, such as hematite in the ocean floor, through time.

• This supports the theory of continental drift because it demonstrates that periods of pole reversals align perfectly on the ocean floor. It demonstrates an identical pattern on both sides of the spreading centers.

• This demonstrates plate motion!

Evidence of continental drift (Summary)1. Plates/continents fit together like puzzle pieces2. Fossil evidence- dinosaurs and plants on Antarctica3. Same type and ages of rocks found on Africa and South America4.Seafloor Spreading- new rock created along the ocean floor5.Paleomagnetism- shows a pattern of identical pole reversal on both sides of a spreading center.

The Dwyka Tillite (rocks layers shown) correlates with similar rocks in South America, India, Australia, and Antarctica.  Alfred Wegener considered this uplifted rock layer to be evidence of continental drift.  

Layers of the Earth A. Crust- solid, 5-70 km thick

Two Types of Crust:Oceanic- ocean floor,

more dense then because of more iron

Continental-dry land

B. Moho- boundary between mantle and crustLithosphere- upper part of the

mantle, almost like crustAsthenosphere- softer layer

under lihtosphere

C. Mantle-(lower) melted, “plastic” magmaD. Outer Core- liquid metalE Inner Core- solid metal (iron and nickel)

Convection currents in the mantle

-The “plasticity” of the mantle allows the plates to glide and move along the mantle creating mountains, trenches and new land.-Heat from the core and the mantle itself causes convection currents to be created in the mantle.-The warmer magma at the bottom of the thick mantle is warmer because it is closer to the core. Warm magma is less dense and rises to the top of the mantle, then it cools and sinks again, creating a constant circulation in the mantle.

This diagram shows how the moving plate boundaries move and create different landforms.

Convection Currents

Divergent creates new ocean floor!

Convergent creates

mountains and volcanoes!

Which plate do we live

on?

Plate Tectonics- the study of the movement of thin slabs of crust called tectonic plates.

Three types of plate boundaries:1. Convergent- two plates coming together2. Divergent- two plates separating3. Transform- two plates sliding past each other.

http://www.msnbc.msn.com/id/7807001

California lies on a strike-slip fault. So, will it ever fall off into the ocean?

NO!The only possibility is that the western half of California will float north (up the coast of the U.S)

Three Types of Convergent Plate Boundaries

A. Continental-Continental- Creates Mountains. (Example ?)

B. Oceanic-Oceanic- More dense plate sinks & melts. Magma rises up and creates island volcanoes. (Ex: Fiji)

C. Continental-Oceanic-oceanic sinks and comes to the surface and creates land volcanoes.(Example: ???)

Oceanic crust sinks, why?

Volcanoes and Plate TectonicsVolcano- a weak spot in the crust where magma comes to the surface.

There are about 600 active volcanoes on land and many more beneath the sea.

- Ring of Fire: an area of active volcanoes that form along the Pacific Plate boundary.

Tectonic Plates of the World

The Tectonic Plates of the World