Concept of PLATE AND PLATE TECTONIC

PLATE TECTONIC THEORY

Plate tectonic theory is a significant concept in 1960 on the basis of continental drift theory and sea floor spreading. In this section we will learn about the concept of plate and their movement.

CONCEPT:-

The plate tectonic is most significant theory explaining the movement of seven large scale plates over the asthensphere.THE RIGID LITHOSPHERIC SLABS OR RIGID AND SOLID CRUSTAL LAYERS ARE TECHTONICALLY CALLED PLATES.(SAVINDER SINGH). So that the process in which the plates moves, interacts, and deforms is referred to as plate tectonics. The plate tectonics is based on two concepts i.e. (I) continental drift theory (II) sea floor spreading.

“Moving over the weak asthenosphere, individual lithospheric plates glide slowly over the surface of the globe ; much as a pack of ice of the arctic ocean drifts under the dragging force of currents and winds”( A.N. STRAHLER and A.H.STRAHLER,1978)

The concept of plate was first used by Canadian geophysicist JOHN TUZO WILSON in 1965.MACKANZIE AND PARKER discussed in the mechanisms of the motions of plates on the basis of GEOMETRICAL THEOREM OF EULER IN 1967. In 1967 ISACKS and SYKES confirmed the “PAVING STONE HYPOTHESIS “. In 1968, W.J.MORGAN and L.PICHON described the aspects of plate tectonics. Therefore the concept of plate tectonics is not related to a scientist’s concept rather than many scientists contributed.

MAJOR PLATES:-

The main eight plates are as under:

African Plate Covering Africa - continental plate

Antarctic Plate Covering Antarctica - continental plate

Australian Plate Covering Australia - continental plate

Indian Plate Covering Indian sub continent and Indian ocean - continental plate

Eurasian Plate Covering Asia and Europe - continental plate

North American Plate Covering North America and North- East Siberia - continental plate

South American Plate Covering South America - continental plate

Pacific Plate Covering Pacific ocean- oceanic plate

MAJOR PLATES

MEDIUM PLATES:-

20 Medium plates are identified. Some notable plates are as under:-

The Arabian plate covering Arabian island and surrounding regions

The Caribbean Plate covering the central America, Northern part of South America and Caribbean sea

The Juan de fuca plate covering the western part of North America

The Nazca plate covering western part of South America

The cocos plate covering western part of central America

The Philippines plate covering the Philippines Island, south china sea and western part of pacific ocean.

The scotia plate covering the scotia sea between south America and Antarctica

MINOR PLATES:-

Some notable minor plates are identified .those are

§ panama plate

§ Somali plate

§ Adriatic plate

§ Madagascar plate

§ Yangzi plate

§ Iranian plate

§ Myanmar plate

§ Tonga plate

§ Greenland plate

§ Sri lanka plate

Each plate is 70 to 100m thick and the area of the most of the plates is large in comparison to depth or thickness of plates. All plates moves over asthenosphere.

NATURE OF PLATES:-

§ Plates are made of granitic and basaltic rock

§Plates are mainly continental and oceanic type

§ Plates are always mobile.

§ The average depth of continental and oceanic plates are 148 and 72 km respectively

HOW PLATES MOVE?

Plates are mobile in nature and they move over asthenosphere. They move in three ways. All tectonic activities are occurred along these plates.

i. Plates move in opposite direction. It is also called constructive margin .when two plates moves opposites to each other, there is upwelling hot molten magma and spread over the region. The new oceanic crust is continuously formed