Page 115 - Social Studies 7

External Elements

Rivers, wind, glaciers, temperature, etc. are the external elements or the factor
that change the surface of the earth.

1. River

A water body that usually
originates from mountain and
flows to the seas and oceans is
known as the river. While flowing
down it cuts its banks or sweeps
away the top soil and sub-soil
and deposit in the lower course.
Due to the deposition of eroded
materials in the Terai the plain
land has become more fertile. It
forms various land features like
oxbow lakes, tributaries, delta, Tamor river
gorge, etc.

2. Wind
Wind is a moving air. It
is one of external forces that
change the surface of the earth.
It is lightly effective in deserts
or in open area. Wind creates
many unique features by its
action of erosion, transportation
and deposition. Some of the
examples are sanddunes, Gara moving air
or mushroom rock, etc.

3. Glacier

Glacier is a thick mass of ice
moving downhill the mountain.
Glacier brings noticeable
changes on the earth's surface.
When snow receives heat of the
sun it melts little and moves
very slowly, hardly 1 or 2 cm in
a day. It carries pebbles sand
soil, etc. while moving downhill.
glacier

115 Dynamic Social Studies and Population Education - Book VII