Transcript Coastal Deserts

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1
Extreme
Environments
Hot
Deserts
What are Hot
deserts like?
Features of hot deserts
Hot Deserts have many different features:
- They are all dry and arid
-They may have a sandy, rocky or stony surface.
- They have very little rainfall
-They are often a lot hotter during the day, than at
night (a large diurnal temperature change)
2
Extreme
Environments
Hot
Deserts
Why are these
Deserts so Hot?
Reason 1  Distance of Travel
Parallel rays
of sunshine
Deserts are hot because of their proximity to the equator. Ray B
has to travel further, through the atmosphere, dust & clouds,
therefore not as
much heat reaches
the poles. Whereas
Ray A has a
shorter distance to
travel – meaning
that it retains more
of the heat from
the sun.
3
Extreme
Environments
Hot
Deserts
Why are these
Deserts so Hot?
Reason 2  Angle of Suns rays
Parallel rays
of sunshine
Deserts are hot because of their proximity to the equator. The earth
is curved. This means that the energy from Ray B is spread/
dispersed over a
X
greater area – the
energy is less
intense. This is
shown by ‘X’ on the
picture.
Whereas the energy
Y
from Ray A is
concentrated on a
smaller area. This is
shown by ‘Y’ on the
Diagram.
4
Extreme
Environments
Hot
Deserts
Why do deserts
receive very little
rainfall?
To understand why deserts receive little
rain, we first need to know why rain occurs.
Rain only forms when moist air rises, cools and
condenses. Often this is by:
Convection current – The sun heats the earth, which heats
the air above it. The air becomes less dense, rises & then
condenses. E.g. Tropical Rainforests at the equator
Frontal Rain – Two air masses meet. One is less dense
than the other and is forced over the top of the other one.
Meaning that it rises, cools and then condenses. E.g. UK
Relief Rain. An air mass is forced over an area of high land.
The air rises, cools and condenses. E.g. in Hilly areas
Why do deserts
Hot
Extreme
receive very little
Environments Deserts rainfall?
In deserts, the air does not contain much
moisture & the air is usually falling meaning
that it cannot condense to produce rain.
Reasons why air falls:
Trade Winds - Due to suns heat, air rises at the
equator & falls near to the tropics (Cancer/Capricorn)
Rain Shadow - Air blows across a mountain. The
air then loses all of its moisture on the other side
Coastal Deserts - If the ocean is particularly
cold, then the air around the coast is cooled,
meaning that it will not rise & condense
5
How does wind
Hot
Extreme
affect how dry the
Environments Deserts desert is?
The prevailing (most common) wind direction
also plays a very important role in desert
climates. E.g. The Prevailing wind for the
Sahara desert in Africa
is from the North East.
This wind blows over
land, so is quite ‘dry air’
as it does not pick up
moisture from the sea.
The same is true for
other deserts.
6
7
Rain Shadow
The rain gets forced up
and over the (windward)
side of the mountain. As
the air rises, it cools &
condenses. The
rain falls over the
mountains. By
the time the
clouds reach the
other (leeward)
side there is no
moisture left in
the air (e.g.
Atacama desert)
8
Coastal Desert -Caused by cold Currents
Cold ocean currents affect the climate of the
coastal area. The colder sea cools down the land
Which means that
the air is cool and
not able to rise.
Sea fog can form
on the coast.
Some plants have
adapted so they
are able to use
Cold
the moisture from
Currents
the fog.
9
Rain &
clouds
TRADE WINDS
The sun is most powerful at the
equator. Here, the sun heats the
earth (A) and the air Rises = low
pressure system. As the air
rises, it cools and condenses
forming cloud (B) and rain
(C). This is why tropical
Rainforests have so much
rain. The air then moves
away from the equator.
Before it then falls. The air
then starts to fall at approx
300N (D) & 300S of the
equator (E). As it falls, it
warms up - the air can’t
then produce rain = High
Pressure system
10a
Extreme
Environments
Hot
Desert
How have people
reacted to Hot Deserts
(media)
Hot deserts are depicted in a number of ways
through different types of media.
Accounts of historical expeditions The extremes of
deserts may be stressed, & meeting different cultures.
E.g. Across the empty quarter  Thesiger
Through films Lawrence of Arabia, The English
Patient, Flight of the Phoenix,
Historical Newspaper articles  “Across the sahara
by caterpillar” The Observer Jan 14th 1923, by Major
Gordon Home &The Murder of Major Gordon Laing
Guardian August 2nd 1828
10b
Extreme
Environments
Hot
Desert
How have people
reacted to Hot Deserts
(poems)
In what ways
does this
poem depict
the desert as
an extreme
environment?
What poetic
techniques
are used?
11
Extreme
Environments
Hot
Desert
How have people
reacted to Hot Deserts
(films)
You need to know examples of different
films that are set in deserts & how the
depict deserts in different ways
127 hours – Adventure
film about endurance in
a hostile environments
The English Patient –
A love story during a
period of war, showing
the romance of the
desert desolation
Lawrence of Arabia –
A film showing the
importance of desert
areas and group in war
12
Extreme
Environments
Hot
Desert
How have people
reacted to Hot Deserts
(Historical reports)
Historical
reports:
An example
of the start of
a report from
Wilfred
Thesiger.
How do
historical
reports such
as these
depict
deserts?
13
Extreme
Environments
Hot
Desert
How have people
reacted to Hot Deserts
(media)
Through TV  Bear Grylls, Travel Programmes,
Michael Palin (Sahara and Pole to Pole)
Through Paintings ‘Pear Blossom Highway’
Hockney. ‘St John in the desert’ Veneziano
Through Music Sometime traditional music or a
‘modern take’ on traditional themes
Each source of information will depict the desert in a different
way. Sometime they will focus on the hardships of the desert
and sometimes they will focus upon the difficulties. The
desert may be portrayed much more positively - the mystical
quality/romance of the desert may be highlighted.
14
Extreme
Environments
Paintings  The
use of colour and
texture can be
important to depict
deserts in order to
invoke different
feelings
Hot
Desert
How have people
reacted to Hot Deserts
(paintings & photos)
Photos  The
viewpoints and
composition can
be important to
depict deserts in
order to invoke
different feelings
15
Extreme
Environments
Names of some
of the world hot
deserts
Hot
Deserts
Where are hot deserts
found?
When describing the distribution
of hot deserts, refer to:
Distances
Compass
directions
Proximity to
other physical
features, such
as mountain,
rivers, sea etc.
16
Extreme
Environments
Hot
Deserts
Where are hot deserts
found?
Hot deserts are found near to the tropic of Capricorn & Cancer &
Often between 150 - 300 N & South of the Equator. This is an area
of high pressure-‘air falls’ due to the Hadley cell