PLATE TECTONICS

Plate Tectonics Plate - large rigid slab of solid rock Tectonics from the Greek root “to build” • A relatively new area of study.

• Formed 30 yrs ago, incorporating seismology and paleontology – Seismology - the study of earthquakes – Paleontology - the study of fossils

Tectonic Plate Theory • a solid lithosphere floating on top of the asthenosphere gives an idea of how plates can float

Evidence to support Tectonic Theory – Initial ideas of continental drift • jig saw puzzle or map fit of continents

Evidence to support Tectonic Theory • map fit--already mentioned • mountain chains formed on continents with longitudinal axes perpendicular to movement of the continents--examples: Himalayan, Rocky Mountain and Andes Mountain chains • same fossils (in rocks),same rocks , mountain ranges, and glacial features located on different continents in areas representing prejoined positions prior to continental drift

Matching of Fossils from Common Locations on Separated Continents

Matching of Mountain Chains from Common Locations on Separated Continents

Matching of Glacial Deposits from Common Locations on Separated Continents

Global Ocean Ridge

•presence and shape of global ocean ridge –a ridge is a raised region on ocean basin which is believed to represent prejoined or splitting area of separated continents--the shape of the ridge contours shape of coast lines of separated continents--- this is most evident in the mid Atlantic ocean

HEAT CAUSES PLATES MOVEMENT – convection cells in Earth’s interior is the force which split the lithosphere and are the driving force in continental separation

Plates of the World • Seven large and many smaller plates • 80 km thick • THREE TYPES OF MOVEMENT.

–

CONVERGENT

- oceanic and continental plates collide forcing the oceanic plate to slide beneath.

–

DIVERGENT

- plates move away from each other, where they diverge molten rock rises.

–

TRANSFORM

- plates move horizontally past each other.

Features Created • Plates move sideways, apart or together • Movement produces three tectonic processes…folding, faulting (diastrophism), volcanism • These movements create landform and ocean features.

Divergent Plates

DIVERGENT PLATE BOUNDARY

Divergent Plates • kinds of divergent plate boundaries--1)ocean basin to ocean basin boundary;

example is the mid ocean ridge

Global Ocean Ridge

DRIFT AND PLATES • 2) continental to continental boundary

Map of East Africa

-- a so-called

triple junction

(or

triple point

),

- three plates are pulling away from one another: the Arabian Plate, and the two parts

of the African Plate

(the Nubian and the Somalian

)

splitting along the

East African Rift Zone.

East Africa may be the site of the Earth's next major ocean. Plate interactions in the region provide scientists an opportunity to study first hand how the Atlantic may have begun to form about 200 million years ago. Geologists believe that, if spreading continues, the three plates that meet at the edge of the present-day African continent will separate completely, allowing the Indian Ocean to flood the area and making the easternmost corner of Africa (the Horn of Africa) a large island.

Convergent Plates

3 types of convergent plate boundaries 1) Ocean basin to continental boundary (Example is the Cascade Mountain chain)

Convergent Plate boundary

2) Ocean basin to ocean basin boundary (Examples are Aleutian Islands and Japan)

Aleutian Islands and Japan

3) Continental to continental plate boundary (Example is India and Asian continent boundary)

Transform Plates

DRIFT AND PLATES •

transformed boundary

--plates move parallel to boundary

Example are those off the Coast of Western U.S.A

.