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

Textbook pp 356-357

• Convection in the Mantle animation• http://www.classzone.com/books/earth_science/terc/content/visualiz

ations/es0805/es0805page01.cfm?chapter_no=visualization

Plate Tectonics

Earth’s Lithosphere is broken into Plates

Each Section Moves

Plate – large pieces of crust that “float” on top of the Asthenosphere in the Mantle.

• Plates move at a rate of several centimeters per year (as fast as your fingernails)

• Plates & Continents drift over the Earth’s surface.

2 Theories

• Continental Drift – All the continents were once one large “Pangea” and have slowly drifted apart about 225 million years ago

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0806/es0806page01.cfm?chapter_no=visualization

• Plate Tectonic - The Earth’s plates are in constant motion. They move because of Convection Currents in the Asthenosphere.

Convergent BoundariesPlates that collide:Continent & Continent

Continent & Ocean

Ocean & Ocean* One goes underneath the other* They both push up.

Convergent

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

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

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

Active volcanoes are confined to northern Costa Rica because the subducted Cocos plate is relatively deep there. In contrast, almost no volcanic activity happens in the south because of processes directly or indirectly related to the subduction of the Cocos Ridge. http://www.gsdidocs.org/gsdiconf/GSDI-9/papers/TS57.3paper.pdf

Divergent Boundary

• Two plates moving AWAY from each other.

• Causes big cracks where lava comes up and forms new land. Mountain Ridges & valleys.

Divergent

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

Ex: Mid-Atlantic RidgeNorth American Plate moving away from Eurasian Plate

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

Aerial view of the area around Thingvellir, Iceland, showing a fissure zone (in shadow) that is an on-land exposure of the Mid-Atlantic Ridge. Right of the fissure, the North American Plate is pulling westward away from the Eurasian Plate (left of fissure). This photograph encompasses the historical tourist area of Thingvellir, the site of Iceland's first parliament, called the Althing, founded around the year A.D. 930. Large building (upper center) is a hotel for visitors. (Photograph by Oddur Sigurdsson, National Energy Authority, Iceland.)

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

Transform Boundary• Two plates slide past each

other going in opposite directions

• Creates rifts in the Earth. Great Earthquakes. Stress from land pulling against each other & suddenly “jerk” apart.

Transform Faulthttp://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/

es0804page01.cfm?chapter_no=visualization

Aerial view of the San Andreas fault slicing through the Carrizo Plain in the Temblor Range east of the city of San Luis Obispo. (Photograph by Robert E. Wallace, USGS.)

Hot SpotsA hole in the plate that goes down to the Asthenosphere. Moves with the plate, leaving a volcanic island behind (Oceanic Crust)

Wahaula Visitor Center, Hawaii Volcanoes National Park, was one of more than 200 structures overrun by lava flows (foreground) from the 1983-present eruption at Kilauea Volcano. (Photograph by J.D. Griggs, USGS.)

Snow-capped 4,169-m-high Mauna Loa Volcano, Island of Hawaii, seen from the USGS Hawaiian Volcano Observatory. Built by Hawaiian hotspot volcanism, Mauna Loa -- the largest mountain in the world -- is a classic example of a shield volcano. (Photograph by Robert I. Tilling, USGS.)

Ring of Fire• Area surround the Pacific Ocean.

• An area of volcanoes & earthquakes that ring the Pacific Plate.

• The Pacific Plate moves

• North American Plate• South American Plate• Eurasian Plate• Indo-Australian Plate• Pacific Plate• Antarctic Plate• Nazca Plate• African Plate

Major Tectonic Plates