Land forms produced by Internal and External processes of Earth

Internal and external processes of the earth are responsible for the continuous physical changes that are taking place on the Earth’s surface from time immemorial. The forces which produce physical features are

Basic Differences between Internal and external processes. The internal process leads to the up-liftment and sinking of the earth’s surface, whereas the external process is the continuous wearing down and rebuilding of the land surface.

External process occur on the surface of the earth .

• It is slow change .
• Ex- change in level of the earth .

Internal process occur inside the surface of the earth .

• It is sudden change .
• Ex -earthquake activities

A. Internal (operate within the Earth’s crust)

I. Earth Movements
(i) Vertical (up and down) movements cause faulting of the crustal rocks.

Features produced : Plateaus; block mountains (horsts); basins; some types of escarpment.

(ii) Lateral (sideways) movements cause folding of the crustal rocks.

Features produced - fold mountains; rift valleys; horsts; block mountains

II. Volcanic Eruptions
(i) External (lavas reach the Earth’s surface)

Features produced : lava plains and plateaus; volcanic cones; geysers

(ii) Internal (lavas solidify in the crust)

Features produced : dykes; sills; batholiths; laccoliths

Core of Earth

INTERNAL FORCES — EARTH MOVEMENTS (TECTONIC) 

The slow and steady changes inside the Earth’s crust are called secular changes. These changes occur due to the forces working within the Earth. These are called Tectonic Movements. These are very slow and have been working for thousands of years. They are primarily responsible for the major physical features such as mountains, plateaus and plains.

These movements are of two types — vertical movements and horizontal or lateral movements.

Vertical Movements or Epeirogeny

When a part of the Earth’s crust sinks or slides down compared to rest of the area, it is called a subsidence. As a result some parts of the Earth are elevated or lifted out of sea floor and some areas submerge under sea water. Thus, these movements are also referred to as continent building or plateau building movements They are basically related to rock displacement which take place in up and down movement. However, the horizontal level arrangement of the crust remains undisturbed. For example, Scandinavia is rising and coastal areas of Alaska are sinking. These movements affect vast areas.

Horizontal Movements

These are also called Orogeny and are more complex movements as they cause disturbance on the Earth’s surface, sometimes beyond recognition. Two types of forces are involved in horizontal movements. They are called Forces or Tension and Compression.

B. External (operate on the Earth’s surface)
I.Denudation
(i) Weathering (the break-up of rocks by alternate heating and cooling; chemical actions, and the action of living organisms).

Features produced : soil; earth pillars (by rain action)

(ii) Erosion (the break-up of rocks by the action of rock particles being moved over the Earth’s surface by water, wind and ice).

Features produced : valleys; peneplains; cliffs, river and coastal terraces; escarpments (in) Transport (the movement of rock particles over the Earth s surface by water, wind and ice)

II.Deposition
(i) By water (river or sea)

Features produced : flood plains; levees; alluvial fans; deltas; beaches; lake plains; marine alluvial plains

(ii) By Ice (ice sheets and valley glaciers)

Features produced : boulder clay plains; out-wash plains; moraines; drumlins; eskers

(iii) By Wind

Features produced : loess plains; sand dunes

(iv) By living organisms (e.g. coral) features produced : coral formations

(v) By Evaporation and Precipitation -Features produced : salt deposits

(vi) Of Organic Matter- Features produced : coal deposits