Plate tectonics The Key to understanding mountain formation

Plate tectonics: The Key to understanding mountain formation

Plate boundaries • . . DocumentsCLASSESMtn_geog10 Videosess 01_int_boundariesess 05_int_bou ndaries. html

Volcanoes, earthquakes • . . DocumentsCLASSESMtn_geog10 Videosess 02_int_tectonicess 05_int_tectoni c. html

World’s tectonic plates

Earth’s Topographic Regions Clue #1: Mountain ranges found only in certain areas (edges of continents)

Marine fossils on top of Everest • Granite core • sedimentary rock layer • Limestone (top) Clue #2: Material composition of mountains N side, view from Rongbuk Monastery, Tibet

Clue #3: Continental Shields in interior of continents

GEOLOGY OF THE USA Craton (kratos; Greek for strength) • old and stable part of the continental crust that has survived the merging and splitting of continents • interiors of continents • formed of a crust of lightweight rock, e. g. granite, attached to a section of the upper mantle.

Clue #4: Ocean crust oldest near continents and youngest towards middle of oceans oldest youngest

Plate motion • Plates move away from, toward, or slide past each other. • There are 3 types of plate boundaries: - divergent - convergent - transform.

Three types of plate boundary

A. DIVERGENT PLATE BOUNDARY • occur along spreading centers where plates are moving apart • new crust is created by magma pushing up from the mantle

Example: Mid-Atlantic Ridge • a topographically high area near the middle of the Atlantic Ocean • splits nearly the entire Atlantic Ocean north to south,

Divergent: Atlantic Ridge LAVA FOUNTAINS KRAFLA VOLCANO ICELAND

B. CONVERGENT PLATE BOUNDARY • Plates are moving toward each other • destruction (recycling) of crust takes place along convergent boundaries Sometimes, pne plate sinks (is subducted) SUBDUCTION ZONE

Convergent plate boundaries 3 types depending on type of plate involved: • Oceanic-continental convergence • Oceanic-oceanic convergence • Continental-continental convergence

1. Oceanic-Continental Collision • oceanic Nazca Plate is pushing into and being subducted under the continental part of the South American Plate • South American Plate is being lifted up, creating the Andes • Strong, destructive earthquakes • rapid uplift of mountain ranges are common in this region.

Oceanic-continental: Pacific RING OF FIRE

Example: Andes Mtns West margin of the South American continent • oceanic Nazca Plate is pushed toward and beneath the continental portion of the South American Plate • typical example of a convergent plate boundary

ALPAMAYO, CORDILLERA BLANCA

2. Oceanic-oceanic Collision Subduction processes in oceanic-oceanic plate convergence result in the formation of volcanic arc islands

Examples of volcanic arc islands • • • Aleutians the Kuriles Japan the Ryukyus, the Philippines Indonesia

3. Continental-continental Collision • neither plate subducted because the continental rocks are relatively light • like two colliding icebergs, plates resist downward motion

HIMALAYAS collision between the Indian and Eurasian plates has pushed up the Himalayas and the Tibetan Plateau

C. TRANSFORM BOUNDARY • At a transform plate boundary, plates slide past each other. • Crust neither produced nor destroyed

Example: San Andreas fault in California Pacific Plate slides past the North American Plate.

Special case: HOTSPOTS “Plume” = huge column of upwelling lava

HOTSPOTS HAWAII VIDEO http: //www. teachersdomain. org/resource/ess 05. sci. ess. ea rthsys. hawaii/

How fast are plates moving? • The Arctic Ridge – slowest rate (less than 2. 5 cm/yr) • East Pacific Rise near Easter Island, in the South Pacific about 3, 400 km west of Chile – fastest rate (more than 15 cm/yr).

Plate Motion Summary

Mountain Maker, Earth shaker • Interactive media