DE LA SALLE COLLEGE Geography Department
Ms.Diane Sammut
TOPIC 4
NOTES
Deserts
2
We will be focusing on...
Page
What are deserts? 3
Characteristics of Hot Deserts 4
How do hot deserts form? 5
Desert landforms 6
Location of hot deserts 7
Animal and plant adaptations in hot deserts 8
People of the hot deserts 10
Desertification 12
Desert dangers 14
Case Study : Thar Desert, India 15
Characteristics of Cold Deserts 16
Cold deserts of the world 17
Animal adaptations in cold deserts 19
Plant adaptations in cold areas 20
Living in cold deserts 21
Blizzards 23
This topic will be addressing the following learning outcomes :
8.7 I can compare the landscape and climate of a hot and a cold desert and the adaptations of vegetation, animals and people to survive this environment.
8.8 I can explore how people exploit hot and cold deserts for economic use.
3
What are DESERTS ?
We've all seen deserts in the movies. They are full
of miles and miles of sand dunes. However, not all
deserts are like this. Many deserts are rocky with
scattered plants and shrubs. There are even deserts
that are icy and cold.
Deserts are primarily defined by their :
lack of rain (they generally gets less then
250mm of rain in a year)
dry soil
little to no surface water
high evaporation (they are so dry that
sometimes rain evaporates before it can hit the
ground!)
living conditions are hostile for plant and
animal life
There are four types of deserts:
subtropical deserts (hot and dry all year-
round)
coastal deserts (cool winters and warm
summers)
cold deserts (long, dry summers and low
rainfall in the winter)
polar deserts (cold all year-round)
HOT IN THE DAY, COLD AT NIGHT
Because deserts are so dry and their humidity is so
low, they have no "blanket" to help insulate the
ground. As a result, they may get very hot during
the day with the sun beating down, but don't
hold the heat overnight. Many deserts can
quickly get cold once the sun sets. Some deserts
can reach temperatures of well over 38°C during
the day and then drop below freezing during the
night.
Location of hot deserts.
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Characteristics of HOT DESERTS Hot deserts are found near the tropics of Cancer
and Capricorn. The largest hot desert is the
Sahara in Africa which spans the whole width of
the continent.
Hot deserts have an extreme climate and
challenging environment. There is very little
biodiversity in hot deserts because of the harsh
climate. Few species are strong enough to survive
there. Plants and animals which do survive there
have adapted to difficult conditions. The living
components and the non-living components of the
hot desert rely on one another - a change in one will
lead to a change in the other.
The climate is very hot. Summer day time
temperatures can exceed 40°C. However, at night
the temperature can drop below 0°C.
The climate is very dry with less than 250 mm of
rainfall a year.
Hot deserts have two distinct seasons:
summer, when the temperature ranges
between 35-40°C, and
winter, when the temperature ranges
between 20-30°C.
Desert soils are thin, sandy, rocky and generally
grey in colour. They are also very dry. When it
does rain they soak up the water very quickly. The
surface of the soil may appear crusty. This is due to
the lack of rainfall. As it is so hot water is drawn up
to the surface of the soil by evaporation. As the
water evaporates, salts are left behind on the
surface of the soil.
WHAT ARE CLIMATE GRAPHS?
Climate graphs show average rainfall
and temperatures typically
experienced in a particular location.
The temperature is shown on a line
graph, and rainfall on a bar graph.
They are usually represented on the
same set of axes with the months of
the year along the base.
Hot desert landscapes.
5
Deserts are formed by weathering processes.
Large variations in temperature between day and night
put pressure on the rocks which then break in pieces.
Although rain seldom occurs in deserts, there are
occasional downpours that can result in flash floods.
Rain falling on hot rocks can cause them to shatter and
the resulting pieces and rubble spread over the desert
floor are further eroded by the wind.
Wind picks up particles of sand and dust and moves
them along in sand or dust storms. Rocks are
smoothed down, while the grains end up piled high in
sand dunes.
How do hot desrts FORM?
Wind erosion process in the desert.
Wind forming sand dunes.
6
Desert LANDFORMS
What is an OASIS? A lone palm tree and a spring in the middle of a sandy desert is the typical image that people have of an oasis. This is a fairly accurate picture, though an oasis can be small or very large. An oasis is any area in a desert that has a supply of freshwater and where plants can therefore grow.
Oases provide rest, shade, food, and water for nomads as they travel their territory and to other people following trade routes. Some peoples have considered oases to be sacred places.
An oasis may be permanent or temporary. A permanent oasis is found where an underground water source exists. Sometimes the water springs naturally from the ground. Other times it is so deep that people must drill down to reach it and bring it up to the surface. The origin of the water may be hundreds of miles away. The water flows underground until it comes to the surface at the oasis.
Some oases exist only temporarily because the water supply is not constant. In the Sahara of Africa, for example, dry streambeds called wadis sometimes fill with water, which allows plants to grow. An oasis in the Sahara desert– Libya.
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Where are hot deserts LOCATED? Deserts cover more than one-fifth of the Earth’s
land area, and they are found on every continent.
Hot deserts are mainly found around the Tropics
of Cancer and Capricorn. The hot deserts of the
world are located between 15° and
30° north or south of the equator, where the air
is sinking air. Air that rises due to the intense heat
at the equator divides to flow north and south.
Deserts are often found towards the west of
continents. Some deserts are found on the western
edges of continents. They are caused by cold ocean
currents, which run along the coast. They cool the
air and make it harder for the air to hold moisture.
Most moisture falls as rain before it reaches the
land.
HOT DESERTS OF THE WORLD
Sahara Desert
The Sahara Desert is the world's largest hot desert; it stretches over 3,500,000
square miles in Northern Africa. he Sahara is a desert located on the African
continent. It is the largest hot desert in the world, and the third largest desert
overall after Antarctica and the Arctic.
The Great Victoria Desert
The Great Victoria Desert stretches across 163,900 square miles in both South
Australia and Western Australia.
Arabian Desert
Summers in the Arabian desert are quite
intense; temperatures can reach as high as
129 °F.
Syrian Desert
The Syrian Desert stretches across 200,000 square miles and only received
about five inches of rain annually.
Kalahari Desert
The Kalahari Desert is a large, arid, sandy area in Southern Africa extending
350,000 square miles.
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The ability to adapt to arid conditions can mean the
difference between life or death for animals and plants
that live in the desert. Some animals ;
burrow deep underground in the heat of the
day
lie in the shade until late afternoon or early
evening
have evolved salt glands, which allow their
bodies to remove salts but not sweat so they
retain water
Most deserts have dry, arid climates with little to no
rain, so every living organism that lives there must
find a way to adapt, survive and thrive, or die.
At night, the desert comes alive. A universal
adaptation of desert living begins with an upside-
down day. Instead of sleeping at night, nocturnal
animals sleep during the hottest part of the day, only
to take up their business of hunting food during night
time. By sleeping in the day, usually in the shade
beneath rocks, in a burrow dug into the cool
underground or beneath the shade of a bush, they
preserve their body’s water. This applies to mammals,
insects and reptiles of the desert.
How do desert plants and and animals ADAPT?
Camel adaptations in the desert.
The Meerkat
9
Native Americans familiar with desert life could
always find water when it couldn’t be found on
land, by slicing open a cactus or taking pieces of
the cactus flesh and eat it. Some cactus can grow to
over 40 feet tall and live for up to 150 years in
conditions that would kill other plants. This tree-
like pillar cactus with arms that shoot out at 90-
degree angles before growing vertically, and seen
in many western movies, survives in the arid desert
because it stores enormous amounts of rainwater
inside its thick, fleshy arms and body, using it
slowly. Many cacti visibly expand during the rainy
season, which also helps them to grow. Some of
them also produces edible fruit that can made into
a fermented beverage for rainfall ceremonies.
Plant adaptations in the desert.
Desert cactus.
The prickly pear.
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PEOPLE of the hot deserts
Deserts are areas with fragile and limited resources.
Despite the harsh conditions people live in desert
areas, but their need for food and water presents many
challenges. The lack of water, food and other basic
means of living are not easily accessible. Still, some
civilizations have attained quite high living standards,
like that of Egypt and some are going well enough to
spend their life here, like Bedouin Arabs. However,
some like the Bushmen of the Kalahari desert are still
quite primitive in terms of living their lives and are
barely surviving.
THE TUAREGS
The Tuareg people are a large Berber ethnic group.
They principally inhabit the Sahara in a vast area
stretching from far southwestern Libya to southern
Algeria, Niger, Mali and Burkina Faso. Traditionally
nomadic pastoralists, small groups of Tuareg are
also found in northern Nigeria. The Tuareg speak the
Tuareg languages.
They have been called
the "blue people" for the
indigo-dye coloured clothes they traditionally wear
and which stains their skin. The Tuaregs have been
one of the ethnic groups that have been historically
influential in the spread of Islam and its legacy in
North Africa and the adjacent Sahel region.
The Tuareg have controlled several trans-Saharan
trade routes and have been an important party to the
conflicts in the Saharan region during the colonial and
post-colonial era.
The Tuaregs travel using camels. The Tuaregs reading Islamic scripture.
Blue coloured turbans worn by the Tuaregs..
Everyday life of Tuaregs.
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BEDOUIN ARABS
The Bedouin are a grouping of nomadic Arab people
who have historically inhabited the desert regions in
North Africa, the Arabian Peninsula, Iraq and the
Levant. The English word Bedouin comes from the
Arabic badawī, which means "desert dweller".
Bedouin territory stretches from the vast deserts of
North Africa to the rocky sands of the Middle East.
They are traditionally divided into tribes, or clans and
share a common culture of herding camels and
goats. The vast majority of Bedouin adhere to Islam.
Many Bedouins have abandoned their nomadic and
tribal traditions for a modern urban lifestyle, however
many retain traditional Bedouin culture such as
retaining the traditional tribe structure, traditional
music, poetry and dance.
Urbanised Bedouins often organise cultural festivals,
usually held several times a year, in which they
gather with other Bedouins. Traditions like camel
riding and camping in the deserts are still popular
leisure activities for urbanised Bedouins who live
close to deserts or other wilderness areas.
The Bedouins in Israel.
Bedouins making bread.
A Bedouin festival in the Sahara.
A typical Bedouin herding sheep.
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DESERTIFICATION — How does it happen?
Desertification is the expansion of desert into the
surrounding areas. The desert area in the world is
getting bigger. Desertification usually happens on
the edge of deserts ex. The Sahel, south of the
Sahara Desert in Africa.
WHAT CAUSES DESERTIFICATION?
Desertification is a complex process. It is caused by
physical processes and human mismanagement.
Factors which may cause desertification include:
climate change - especially long dry periods,
causing drought. The dry conditions cause the
vegetation to die, so the land loses the
protective cover that vegetation provides.
too many animals within the area - leads
to overgrazing.
population growth - leads to more pressure on
the land for growing crops. Nomadic tribes that
once moved around may start to farm in one
area. Wood is also used for buildings, heating,
and firewood, causing deforestation and soil
erosion.
The Sahel region.
People fighting desertification in Burkina Faso—West Africa.
Map showing areas around the world which are most affected by desertification.
Images showing the effects of desertification in Africa.
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WHAT ARE THE EFFECTS OF DESERTIFICATION?
lack of vegetation cover for holding soil together and
for grazing
increased soil erosion
crop failure, leading to famine
fewer plant and animal species
land is unable to support people so they are forced
to migrate
HOW CAN DESERTIFICATION BE SOLVED?
Recent evidence suggests that there are some areas where the process of desertification has slowed down.
However, the areas on the edge of deserts are still fragile and need very careful management.
Desertification in Syria.
____________________________
so plants have a chance to grow
again
____________________________
circles of stones are placed on the
ground to hold water on the soil
rather than let it run quickly across
the surface —this reduces soil
erosion
___________________________
providing shelter from the wind
____________________________
adding layers of leaves or straw
can reduce evaporation and add
nutrients to the soil when they rot
____________________________
soil is not washed down the slope
when it rains
_________________________
used to stabilise sand dunes
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Desert DANGERS Life in deserts is extremely difficult because of the lack of
water, limited food supply and extreme heat during the day
and cold during the night, and exposure to other elements.
In a desert area there are many environmental factors that
challenging :
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You find scorpions in in
many areas including deserts.
They are mostly nocturnal.
Scorpions typically brown or
black in moist areas, however
in the desert they may be
yellow or light green. Fatalities from scorpion stings are rare.
A bite from a scorpion may cause swelling, pain, nausea,
fever, and even speech and breathing difficulties.
Sandstorms occur frequently
in most deserts. Within Saudi
Arabia, winds typically range
from 3.2 to 4.8 kph. The
greatest danger is getting lost
in a swirling wall of sand.
People usually cover their mouth and nose with cloth.
Mirages are optical phenomena caused by the refraction of
light through heated air rising from a sandy or stony surface.
They occur in the interior of the desert about 10 kilometers
from the coast. They make
objects that are 1.5 kilometers or
more away appear to move. This
mirage effect makes it difficult
for you to identify an object from
a distance. The mirage effect
makes it hard for a person to identify targets and see objects
clearly. However, if you can get to high ground you can get
above the superheated air close to the ground and overcome
the mirage effect.
An extreme loss of water and salt
and your body's inability to cool
itself can cause heat stroke.
Persons may die if not cooled
immediately. Symptoms are the
lack of sweat, hot and dry skin,
headache, dizziness, fast pulse, nausea and vomiting, and
mental confusion leading to unconsciousness.
Some species of snakes have
specialized glands that contain a
toxic venom, and long, hollow
fangs to inject their venom.
Although venomous snakes use
their venom to secure food, they
also use it for self-defense. Human accidents occur when you
don't see or hear the snake, when you step on them, or when
you walk too close to them.
Desert survival kit.
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The Thar Desert is
located in northwest
India. It is one of the
major hot deserts of
the world with the
highest population
density. Many people
living in this desert
are farmers but with increasing development
opportunities, the human population is also growing.
Due to population pressures this environment is
increasingly under threat.
Despite having an extreme climate, the Thar Desert
can provide development opportunities. These
include:
Mining - the desert has valuable reserves of
minerals such as feldspar, phospherite, gypsum
and kaolin. These minerals are used to produce a
range of things from cement to fertilisers and are
therefore valuable. Limestone and marble are
also quarried in the area. Limestone is used for
building and producing cement, and marble is
used in construction.
Energy generation - energy is produced in the
Thar Desert using solar panels. This energy is
used to clean water supplies contaminated with
salt (desalination). Wind energy is also used to
generate electricity. A wind farm consisting of 75
wind turbines has the capacity to produce 60
megawatts of electricity.
Farming - irrigation in the Thar Desert has
made commercial arable farming (growing of
crops) viable. Producing crops such as wheat
and cotton has created many jobs and generated
income for the local economy.
Tourism - the Thar Desert National Park attracts
many visitors who want to see some of the 120
species found there. Tourists explore the desert
with local guides on camels. Tourism is an
important source of income and creates many
jobs for local people.
Case Study : THE THAR DESERT, INDIA
Desert safari—a popular activity with tourists.
The growing of crops in the Thar Desert.
Desert solar farm .
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Cold deserts, sometimes known as temperate
deserts, occur at higher latitudes than hot deserts,
and the aridity is caused by the dryness of the air.
Some cold deserts are far from the ocean and others
are separated by mountain ranges from the sea, and
in both cases, there is insufficient moisture in the air
to cause much precipitation.
Polar deserts are a particular class of cold desert.
The air is very cold (average annual temperature is
around -50°C) and carries little moisture so little
precipitation occurs and what does fall, usually
snow, is carried along in the often strong wind and
may form blizzards, drifts and dunes similar to those
caused by dust and sand in other desert regions. In
Antarctica, for example, the annual precipitation is
about 50 mm on the central plateau and some ten
times that amount on some major peninsulas.
WHY IS IT SO COLD AND DRY?
The angle of the Sun is low in the sky. This
means the energy from the Sun spreads out
over a large area.
The area has 24 hours of darkness for some of the
winter. Therefore, there is no sunlight for long
periods of time.
The surface of Antarctica has a high albedo. This
means that a lot of the energy received from the
Sun is reflected back into space.
The high altitude of the land. Temperatures
decrease approximately 1°C for every 100 m
increase in height.
Cold air cannot hold as much water vapour as
warm air, so precipitation is less likely.
Oceans store heat so they often create milder
temperatures and increased rainfall. However, as
Antarctica is such a large land mass most of
which is away from the sea.
Characteristics of COLD DESERTS
Typical climate graph for Antarctica.
The cold desert of the Himalayas.
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COLD DESERTS of the world The largest of these deserts are found in Central Asia.
Others occur on the eastern side of the Rocky Mountains,
the eastern side of the southern Andes and in southern
Australia.
GREENLAND
Greenland is the world’s largest non- continental and coldest desert. It is famous
for having the largest national park in the world, the Northeast Greenland
National Park. Temperature of Greenland remains between –8° to -3.88° Celsius.
GOBI
In Asia, Gobi covers the area of Mongolia as well as southern and western part
of China. Being situated on the enormous plateau, high altitude is one of the
major factors for its cold temperature.
ARCTIC
The Arctic circumscribes the North Pole of the world and extends into several
regions including Alaska, Canada, Greenland, Iceland, Norway, Finland,
Sweden, and Russia.
NAMIB
Namib is located in southern Africa and is known for its cold temperature. The
reason behind cold temperature is its location along the coast of Benguela
current. The interesting fact about it is that many shipwrecks can be found up to
50 meters inland ascribed to the movement of the desert.
TURKESTAN
The desert lies in the region of central Asia. Turkish people used to live here. The
cold desert is also home to gerbils, tortoises, and gazelles. Turkestan Desert is a
desert /semi-desert region of Turkmenistan, Uzbekistan, Kyrgyzstan, Tajikistan,
and southern Kazakh-stan. This 215,000 square mile desert covers five different
countries. Turkestan Desert is a cold desert and has long winters .
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ANTARCTICA
Antarctica is considered as the driest, windiest and coldest continent in the
world. In fact, the world’s coldest temperature was recorded at Vostok Station
in 1983 . The reason behind its weather is landmass elevation and ocean
temperatures.
ATACAMA
Atacama desert is situated in South America. It is
considered as the driest and non-polar desert in the
world. It is also noticed that the Atacama desert has
been described as very similar to Mars’ surface.
IRANIAN
The Iranian desert is famous for its marshes and seasonal lakes due to the
runoff from nearby mountains. Sand storms are very common in this area and
can form mound that reach up to 40 meters in height.
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ANIMAL ADAPTATIONS in cold deserts Cold desert animals, even the ones that also live in
hot and dry deserts, burrow into the ground to stay
warm. Dry desert animals burrow to stay cool.
Animals such as badgers, kit foxes, coyotes and
lizards also burrow into the ground. Only jack
rabbits tend not to. Cold desert animals usually
come out when the temperature is at its warmest.
Cold deserts are also populated by many small
mammals that horde food and are stingy about
what they eat. These include kangaroo rats,
kangaroo mice, pocket mice, grasshopper mice and
ground squirrels. Larger mammals such as
antelopes, deer and camels can also be found in
cold deserts.
Mammals are more likely to appear in cold deserts than
reptiles. With coats of fur and warm blood (meaning
that they can maintain a stable internal temperature
even when the ambient atmospheric temperature dips),
mammals are well-adapted to deal with freezing
winters. However, some lizards and snakes do make
their homes in certain cold deserts.
Polar bears are the world’s biggest land-based carnivores! They mainly eat seals but can hunt small whales. They are found across the Arctic Ocean, in parts of Canada, Alaska, Russia, Greenland and Norway (Svalbard).
Reindeer are a species of deer. They can be found in Northern Asia, Europe, Siberia, Alaska, Canada and Green-land.
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Like many cold environments, plants in cold deserts
tend to be deciduous. They also have spiny leaves,
which can help prevent evaporation or protect the
plant in the fight for scarce resources. Their shallow
and widely spread root systems help absorb as
much water as possible, so they tend to be widely
scattered. Plant height can vary between 6 to 48
inches. Cacti, sagebrush and ocotillo are a few of the
plants that make their home there. Only a select few
have managed to adapt to the harsh habitat.
How do PLANTS ADAPT in cold areas?
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The Sámi are a groupSweden, Finland and
the Kola peninsula in Russia. of indigenous
people that come from the region of Sápmi, which
stretches across the northern parts of Norway,
No-one is exactly sure how many Sámi people there
are, but estimates range from between 50,000 –
200,000! On the 6 February every year, they
celebrate Sámi Peoples Day. They wear traditional
clothes, eat traditional food and fly the Sámi flag!
Their traditional outfits – known as the Gakti – are
worn at parties, festivals, weddings, baptisms,
funerals and more. The handmade outfits are
decorated with different designs so the Sámi can
easily tell where another person is from.
The Sámi are best known
for reindeer herding.
Reindeer meat is used for
cooking, leather and fur is
used to make shoes and
clothing, and antlers and
bones make useful tools
and decorative objects.
The Sámi are also skilled fishers and sheep
herders. Reindeer are so important to the Sámi way
of life, that many people go to a special university to
learn how to care for their animals. Like we might
have classes in Maths or English, they have classes
that teach them how to look after the reindeer herds –
how cool is that?!
There are nine different
Sámi languages!
Thankfully, the word
‘reindeer’ is the same
for all Sámi people,
meaning they can
communicate with each
other about reindeer, no matter what language
they’re speaking!
LIVING in cold deserts
The Sami people.
The regions inhabited by the Sami.
The love and care for reindeer.
Typical Sami clothing designs.
The Sami flag.
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In Frozen II, the make-believe Northuldra tribe you
see in the Enchanted Forest are based on the Sámi
people of northern Norway! During the film, Elsa
and Anna learn that their mother was one of the
Northuldra people, which makes the sisters half
Northuldran.
The Sámi are ‘semi-nomadic’, meaning they don’t
stay in the same place all year. Sámi herders migrate
with their reindeer during the seasons, heading to the
mountains for winter and coming back together with
the community in the summer. On the journey, Sámi
herders will camp in a traditional tent, called a lavvo.
A lavvo is a circular frame of poles leaning inwards
towards a pointy top – similar in style to the teepees
and wigwams used by the indigenous people of
America. Traditionally, the Sámi people lived in a
group of families called a ‘siida‘. The word siida is
used to describe both the reindeer herding area and
the team of people who look after the herd.
The Sámi people have their own parliaments to
represent them in Norway, Sweden and Finland, and
their own newspapers and radio stations, that
report on issues that concern the Sámi people!
Laipi—Sami typical bread and its recipe below..
The Northuldra people in Frozen II
The Sami Parliament in Norway.
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A blizzard is a powerful snowstorm. Low
temperatures, strong winds, and large amounts
of snow together create this dangerous weather
condition. During a blizzard, the driving snow can
make it difficult to see far.
During a blizzard the wind blows at speeds of more
than 56 kilometers per hour for at least three hours.
Visibility (the distance you can see) drops to 0.4
kilometre or less. When the weather conditions are
this bad, main roads and railways may have to be
closed, and power and telecommunications lines
may stop working.
In a severe blizzard, the wind speed increases to
more than 72 kilometres per hour. Visibility drops to
near-zero, and temperatures fall to −12 °C or lower.
When a severe blizzard becomes so bad that it is
impossible to see where the ground ends and the air
begins, it is called a “whiteout.” A ground blizzard
occurs when snow has stopped falling and high
winds are blowing around the fallen snow. Ground
blizzards are most common in wide, open fields or
flat spaces.
Blizzards often occur in cold places where winds
blow strongly—in Antarctica, for example.
However, these storms can happen almost anywhere
in the right conditions.
During the winter of 1962–63 the United Kingdom
suffered some of its most severe weather ever.
Blizzards left drifts of snow 6 meters deep. Roads
and railways were blocked, power lines fell down,
and communities were completely cut off.
In 1993 a blizzard so powerful that it was later called
the Storm of the Century struck the East Coast of
the United States. It affected 26 states and left 3
million people without power. Some places received
more than 1 meter of snow.
BLIZZARDS— dangers in cold areas
Aftermath of the Blizzard of 2015 Includes Floods, Destroyed Homes and Cars.
Effects of a blizzard.
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