What is plate

Tectonics?

?

The Earth is composed of major and minor plates

CrustOceanic crust The thin crust under the oceanscontinental crust denser in natureMantle Under the crust is the rocky mantleLithosphere

Asthenosphere

zones within which relative motion is achieved are relatively narrow, defining large tracts of relatively stable, rigid earth's surface. These are the tectonic plates.

Layers of Earth responsible for Plate motion

Phenomenon of Plate motion

Asthenosphere Its hot and finds a weak place in the lithosphere to rise buoyantly as a plume, or hotspot Occasionally.

Lithosphere – cool and behave as a more or less rigid shell.

Role of Mantle in Plate Movement

a) Convection currents in the mantle

b) Process of convection in heating Water.

What are the driving forces?Convection currents or gravity?

The place where new oceanic crust is formed is called a spreading ridge. An example of a spreading ridge is the Mid-Atlantic Ridge at the bottom of the Atlantic Ocean.

Types of Plate Boundaries

Divergent Plate Boundary

Convergent Plate Boundary

The Boundary of plates where collision takes place are termed as convergent plate boundaries Collision results in Subduction.What is Subduction?These collision can be seen betweenContinent- ContinentContinent – OceanOcean - Ocean

Motion between convergent boundaries

The location where sinking of a plate occurs is called a subduction zone. As it slides below the continental crust, sinking deeper into the hot mantle, the oceanic crust begins to melt. This melted oceanic crust becomes less dense (because it is now in a liquid form) and therefore rises towards the surface causing continental crust to rise up above it, forming mountains and volcanoes and high plateaus.

Continent -continent collisionWhen two continents meet head-on such collision seen.No subduction takes place. Why?

E. g. The Indian plate collision with the Eurasian plate giving rise to present height of Himalayas and Tibetan plateau

Oceanic- Oceanic Convergence

Here Two oceanic plates convergeOne subducts under otherResults –a) Trenches –e.g. Marianas Trench -11,000 mts. DeepVolcanoes that are marine volcanoes Later forming island arcs.

Continental - Oceanic Convergence

This collision takes place between continent and an oceanic plate.The Oceanic plate subducts under the continental plateResults in –TrenchesVolcanic arcs

Transform Boundaries

The zone between two plates sliding horizontally past one another is called a transform-fault boundary, or simply a transform boundary. A famous example of such a collision is the San Andreaes fault in California.

Map showing distribution of fossils on the southern continents. These distributions caused Wegener to join the continents as shown in the map.

2.Continental drift

Evidences

1

The tectonic activities as earthquakes, volcanism at the boundaries of plates. 3

4.

The concentration is striking, and indeed this plot serves to define the plate boundaries extremely well. here are ridges, such as the Mid-Atlantic Ridge where plates are separating that are produced by lava welling up from between the plates as they pull apart. Likewise, there are mountain ranges being formed where plates are pushing against each other (e.g., the Himalayas, which are still growing). Plate tectonic motion, which may be only centimeters per century, is now being studied by careful laser ranging techniques that are capable of detecting such small motions.