Question

According to plate tectonics, how many plates the earth is made up of?
(A) 10
(B) 15
(C) 20
(D) 5

Answer 1

Hint: A tectonic plate is also called a lithospheric plate which is massive, irregularly shaped slab of solid rock, and generally composed of both continental and oceanic lithosphere.

Complete answer:
Plate tectonic theory states that the Earth's outer shell is divided into several plates that glide over the mantle. The plates act like a hard and rigid shell compared to the earth mantle.

 The plates consist of two principal types of material, they are oceanic crust, and continental crust. The earth is considered of 15 major tectonic plates. While Seven of which are primary plates and the rest are secondary plates.

The primary plates are the African plate, the Antarctic plate, the Eurasian plate, the Indo-Australian plate, the North American plate, the Pacific plate, and the South American plate.
The secondary plates are the Arabian plate, the Caribbean plate, the Cocos plate, the Juan de Fuca plate, the Indian plate, the Nazca plate, the Philippine Sea plate and the Scotia plate. And these are the primary and secondary plates of tectonic plates.

The effect on different densities of lithosphere rock can be seen in elevations of continental and oceanic crust. The less dense continental crust has greater buoyancy , and causes it to float much higher in the mantle.

Hence, the correct answer is option (B)

Note: Like many features the earth surface plates can change over time. Those are composed partly of oceanic lithosphere which can sink under another plate. This process is happening in the coasts of Oregon and Washington.