Plate Tectonicshttp://www.middleschoolscience.com 2009

Earth’s LayersThe Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed.

This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

The Crust

• Outermost layer• 5 – 100 km thick• Made of Oxygen, Silicon, Aluminum

Crust

The Mantle• Layer of Earth

between the crust and the core

• Contains most of the Earth’s mass

• Has more magnesium and less aluminum and silicon than the crust

• Is denser than the crust

Mantle

The Core• Below the mantle and to the

center of the Earth• Outer Core-layer of molten

metal, which behaves like a liquid.

• Inner Core – is a dense ball of solid metal-b/c the extreme pressure squeezes the atoms of iron and nickel so much that they cannot spread out and become a liquid.

• Core is believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium

“Both the outer & inner core together are just slightly smaller than the moon.”

Core

Earth’s Magnetic Field

A. Currents in the liquid outer core force the solid inner core to spin.

B. The inner core inside the Earth, spins at a slightly faster rate than the rest of the planet.

C. The spinning movement—creates the Earth’s magnetic field, which is a force that causes the planet to act like a giant bar magnet.1. Like a magnet, Earth’s magnetic field

has north & south poles.

Conclusion

Plate Tectonics

Tectonic Plates

Plate Tectonics

• Greek – “tektonikos” of a builder• Pieces of the lithosphere that move around• Each plate has a name• Fit together like jigsaw puzzles• Float on top of mantle similar to ice cubes

in a bowl of water

Plates

Continental Drift

http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml

Alfred Wegener 1900’sContinents were once a single land mass that drifted apart.

Fossils of the same plants and animals are found on different continents

Called this supercontinent Pangea, Greek for “all Earth”

245 Million years ago

Split again – Laurasia & Gondwana 180 million years ago

Continental Drift

Evidence of Pangea

Ocean Floor

Sea Floor Spreading

Sea Floor Spreading

• Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins

• Magma rises to the surface and solidifies and new crust forms

• Older Crust is pushedfarther away from the ridge

Clues about Ocean Floors(Expedition)

How Plates Move

http://pubs.usgs.gov/gip/dynamic/unanswered.html

Convection Currents

Different Types of Boundaries

http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary – Arabian and African Plates

Divergent Boundary – Iceland

http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary - Oceanic

http://www.geology.com

Divergent Boundary - Continental

http://www.geology.com

Convergent Boundary – Indian and Eurasian Plates

Convergent Boundary – Oceanic & Continental

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundary – Oceanic & Oceanic

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundaries - Continental

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Transform Boundary – San Andreas Fault

www.geology.com

Review

Review

• Name the 3 main layers of the Earth• What is a tectonic plate?• What was Pangea?• What is Sea-Floor spreading?• Name the three different types of plate

boundaries and one location on Earth for each one