Plate Tectonics. Earth’s Layers The Earth's rocky outer crust solidified billions of years...

Plate Tectonics

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• The solid part of earth is called the

lithosphere

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

• The liquid part of the Earth is called the asthenosphere

The Core• Below the mantle

and to the center of the Earth

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

• Gravity draws everything to the core.

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

Plate Tectonics

• The plates move around on the asthenosphere

• The theory that the Earth’s crust is broken into sections.

• Causes earthquakes, volcanoes, trenches and mountains on Earth

Continental Drift• Pangaea• Alfred Wegener suggested

that all the continents were once joined together in the past and broke apart about 200 million years ago. He thought this because of the apparent way that the continents fit together like pieces of a puzzle. The large landmass was called Pangaea.

Continental DriftAlfred 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

Evidence of Pangea

Evidence of Pangaea

• Fossils• Rock formations• Continent shape

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

How Plates Move

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

Different Types of Boundaries

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

Divergent Plate Boundaries

Plates move apart

Ex: Mid Ocean Ridges, Continential rifts

Divergent Boundary – Arabian and African Plates

Divergent Boundary Iceland

Divergent Boundary - Oceanic

http://www.geology.com

Divergent Boundary - Continental

http://www.geology.com

African Rift

Convergent Boundaries

Plates collide

EX: Mountains, trenches, and island arcs

Convergent Boundaries - Continental

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

Convergent Boundary – Indian and Eurasian Plates

Subduction

When an ocean plate sinks beneath a continental plate.

EX: Trenches, volcanoes

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

Island Arcs

• Aleutian Islands • Northeastern Japan arc

• Japan and Ryukyu Islands

• Mariana Islands • Philippines

Transform boundaries

Plates slide past each other.

EX: San Andreas Fault, earthquakes are common on

transform boundaries.

Transform Boundary – San Andreas Fault

www.geology.com

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

Divergent boundaries

Convergent boundaries

Transform boundaries