Plate Boundaries

http://www.absorblearning.com/media/attachment.action?quick=12o&att=2773

Divergent Boundary

1) Divergent boundary• 2 plates move apart• Most occur at mid-ocean

ridge• New crust is created by

magma pushing up from the mantle

Rift valleys occur when boundary is on land

Sea Floor Spreading

Rift Valleys Rift valleys occur when boundary is on land Plates pull apart causing faults in the crust.

Magma fills in and forms new land.

Rift Valley

http://www.wwnorton.com/college/geo/egeo/flash/2_11.swf

• Map showing the Mid-Atlantic Ridge splitting Iceland and separating the North American and Eurasian Plates. The map also shows Reykjavik, the capital of Iceland, the Thingvellir area, and the locations of some of

Iceland's active volcanoes (red triangles), including Krafla.

Lava fountains (5 p;10 m high) spouting from eruptive fissures during the October 1980 eruption of Krafla Volcano. (Photograph by Gudmundur E. Sigvaldason, Nordic Volcanological Institute, Reykjavik, Iceland.)

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.)

One young divergent plate boundary that you'll recognize is actively forming the Red Sea. Although the Arabian peninsula and Africa were once linked to form a single continent, they are now being ripped apart. The white arrows show the directions the two plates are moving. You can see that a new ocean, the Red Sea is being formed as they separate.

• http://www.absorblearning.com/media/attachment.action?quick=12n&att=2771

• http://esminfo.prenhall.com/science/geoanimations/animations/35_VolcanicAct.html

2) Convergent boundary

– 2 plates come together

– Collision occurs

– Density of the plate determines which ends up on top

What Goes On At Ocean-Continent Convergent Plate Boundaries?

•Earthquakes occur as the ocean plate subducts •An ocean trench forms as the sea floor bends •Volcanoes form as magma erupts from the subduction zone •Mountains form as sediments are folded and faulted

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0902/es0902page01.cfm?chapter_no=visualization

• http://education.sdsc.edu/optiputer/flash/subduction_5.htm

• http://esminfo.prenhall.com/science/geoanimations/animations/35_VolcanicAct.html

• http://www.absorblearning.com/media/attachment.action?quick=12s&att=2781

• http://www.classzone.com/books/earth_science/terc/content/visualizations/es0808/es0808page01.cfm?chapter_no=visualization

•Earthquakes occur as one ocean plate subducts •An ocean trench forms as the sea floor bends •A volcanic island arc forms as magma rises above the subduction zone

•Old oceanic plate is more dense than new oceanic plate•Old oceanic plate slides under the new oceanic plate and returns to the mantle

Ocean-Ocean Plate Boundary

• http://education.sdsc.edu/optiputer/flash/convergance2.htm

• http://esminfo.prenhall.com/science/geoanimations/animations/35_VolcanicAct.html

• http://www.absorblearning.com/media/attachment.action?quick=12u&att=2785

Continent-Continent Convergent Plate Boundary

oMountain building occurs as the continental crust is folded and faulted

oEarthquakes occur as two continents collide NO volcanic activity India crashes into Asia Himalayan Mountains and Tibetan Plateau

• http://www.classzone.com/books/earth_science/terc/content/visualizations/es1105/es1105page01.cfm?chapter_no=visualization

• http://www.absorblearning.com/media/attachment.action?quick=12t&att=2783

3) Transform boundary

– Crust is neither created nor destroyed

– 2 plates slip past each other

– Earthquakes frequently occur

– http://www.wwnorton.com/college/geo/earth/flash/4_2.swf

• http://www.learner.org/interactives/dynamicearth/slip3.html