EARTHQUAKES AND TECTONIC PLATE MOVEMENTS

EARTHQUAKES AND TECTONIC PLATE

MOVEMENTS

Introduction

Earthquakes are natural disasters. Earth is our home planet

and quake means shaking or trembling. So, when the earth

is shaking, it is called an earthquake or seismic activity of

the earth. 

Causes of Earthquakes

Plate tectonics is a scientific theory that the earth's

lithosphere (see Layers of Earth) which is made up of the earth's crustand upper part of the mantle, is broken into several

irregularly shaped parts. These parts are called

tectonic Plate. The plates lie on the top of molten

layers of rock called the asthenosphere (see Layers of Earth).The asthenosphere lies in the mantle underneath theless dense lithosphere. These plates move veryslowly over the years. When the tectonic plates

move, the earthquake happens.The tectonic plates are objects or pieces of earth's

lithosphere while the plate tectonic is the action that

involves movements and interactions of these plates

with each other.

The movements of the Tectonic Plates

or The Mechanism of Plate Tectonic 

The research is still going on about the mechanism of

the movements of the tectonic plates (lithosphere).The most accepted theories of the mechanism of the

plate movements are convection current or convection

cycle, ridge push, and slab pull.

Divergent Boundaries:

We all know that as we go deeper into the earth's layers,

the hotter it becomes. This rise in temperature createsa slow-moving convection cycle in the mantle. Due to

this cycle, the hotter materials from the inner layers of

the mantle come up toward the surface. As the hotter

materials accumulate below the lithosphere, the lithosphere

splits due to this convection current and moves in the

opposite direction. It creates divergent boundaries of

the plates. 

When divergent plate boundaries occur between two

oceanic plates, the magma upwells to the ocean bed

and creates a mid-ocean ridge. An example is the

Mid-Atlantic ridge. When two continental plates move

apart and form divergent boundaries, rift valleys formthere. East African Rift Valley was an example of a

continental divergent boundary. The Red Sea also was

formed due to the divergent boundary of the Africanplate and the Arabian plate. Around the mid-oceanicridge, the earth's gravitational pull acts on the young

and raised oceanic lithosphere or plate in divergent

boundaries. As a result, the lithosphere slides down,

and the asthenosphere below the mid-ocean ridge rises

and forms a new lithosphere. This phenomenon is called

ridge push. Ridge push causes volcanic activities in the

mid-oceanic ridge.

Convergent Boundaries:

When the tectonic plates move towards each other,

convergent boundaries form. When two continentalplates collide, neither the plates subduct nor any

magma comes out. Also, the earthquake did not occur.

The two plates buckled and created folded mountains.An example is the creation of the Himalayan MountainRange due to the collision between the Indian Plate and

the Eurasian Plate. When oceanic plates and continentalplates collide, the more dense oceanic plate subductsunder a less dense continental plate due to gravity. This

phenomenon is called the slab pull. As a result, magma

goes up, a result, the magma goes up, and formsvolcanic mountains, earthquakes may occur, and deeptrenches may form. Atacama trench and Lascar volcanic

mountain formed when the oceanic Nazca Plate

subducted below the continental South American

Plate. 

When two oceanic plates collide, the older plate

(denser) subducts under the young oceanic plate

(less dense). The magma comes up as a result and

forms volcanic islands. For example, a portion of

the North American Plate that was covered with

the ocean subducted underneath the Pacific Oceanic

Plate, and as a result, the Aleutian island formed. 

Transform Boundaries:

When the plates move next to each other, they

do not go smoothly creating earthquakes. Hencetransform boundaries of the plate are formed.Unlike other boundaries, transform boundaries

don't produce magma.

Why do we not feel earthquakes everyday?

We know that the tectonic plates move constantly.

But we don't always feel the earthquakes. It isbecause the intensity of the seismic activities or

earthquakes are not always the same. We don'texperience low magnitude activities.

How to measure the earthquake?

The intensity or the magnitude of the earthquake is

measured by a Richter Scale. It shows howdestructive the earthquake was. While a Seismograph

detects the seismic waves.