2. Relief
41
How relief was formed
❚
The
lithosphere
is made up of the crust and the upper part of the
mantle.
❚
The
tectonic plates
move over the
mantle
slowly and continuously.
The plates can separate or collide.
❚
The process of movements of tectonic plates that forms mountains
is called
orogeny
.
The shaping of relief
❚
The main agent in shaping relief is
water
; both marine and
continental water, in a liquid or solid state.
❚
Other agents which help shape relief are the
wind
,
extreme
temperatures
and the action of human beings.
Types of relief on Earth
❚
Continental relief
occupies most of the emerged land. Horizontal
landforms predominate (plains, plateaus, valleys, mountains,
mountain ranges and hills).
❚
Coastal relief
is shaped by agents from oceans and continents.
– The main
coastal landforms
are cliffs and beaches.
– The
coastline
has areas that project into the sea (capes) or the sea
indents into the land (gulfs, bays ad coves). Islands, archipelagos and
peninsulas are off the coast.
– Some
coastal landforms
are created by the action of rivers that
creates deltas, rias, estuaries, lagoons and marshes.
❚
The relief of the
ocean floor
is formed by the continental shelf, the
continental slope and the abyssal plain where deep ocean trenches
and ocean ridges (mountain ranges) are found.
Geological hazards
The forces of the Earth’s interior can cause catastrophic damage.
❚
Volcanoes
are landforms created by the emission of molten materials
(lava), ash and gases to the surface from the interior of the Earth’s
crust.
❚
Earthquakes
are sudden powerful movements of the Earth’s crust,
caused by the liberation of energy from the Earth’s interior in the form
of seismic waves. The shaking and the fractures in the ground can
cause serious damage to buildings. The intensity of an earthquake is
measured on the Richter scale.
❚
Tidal waves
are caused by earthquakes under the sea and can
produce enormous waves called
tsunamis
. If a tsunami reaches the
coast, it can cause catastrophic damage.
❚
The Earth is made up of three layers:
crust
,
mantle
and
core
.
❚
The
crust
is the external layer of the Earth. This
layer is not smooth. There are plains, valleys,
depressions and mountains on the surface. All
these geographical features together are
called relief.
❚
In the
inner core
, materials are in a solid
state. In the
outer core
and the
mantle
,
rocks are molten, called
magma
.
THE STRUCTURE OF THE EARTH
KEY CONCEPTS
2
