Deserts1 Why Are Deserts HotPresentation Transcript
WHy are deserts hot and dry?
What are deserts?
Areas with an average rainfall of less than 100mm a year can be classed as deserts.
Deserts do not have to be hot- they just have to have less than 100 mm of rain a year!!!
hot deserts cold deserts Antarctica ia a desert
Where do we find the major deserts?
Complete your deserts map on your sheet, fill in the name of each desert in the spaces provided
You have 5 minutes
Sonoron Great Victorian Gobi
Where do we find Hot Deserts?
Hot deserts are found at latitudes 30 degrees north and south of the Equator
They are found to the west or centre of CONTINENTS
Latitude and Longitude Lines around the Earth, like the Equator Lines down the Earth, like the Greenwich meridian
What are the major lines called? 23.5 degrees S Latitude Tropic of Capricorn 23.5 degrees N Latitude Tropic of Cancer Where one day jumps to next 180 DEGREES E/W Longitude International date line Divides into East and west 0 degrees E/W Longitude Greenwich Meridian Divides Earth into north and south O degrees N/S Latitude Equator significance degrees Lat/long Line
Equator Tropic of Cancer Tropic of Capricorn Arctic Circle Antarctic Circle 0 º 23 ½º 66 ½º 23 ½º 66 ½º North South 0 º Greenwich Meridian East West International Date Line 180 º Sun overhead 21 June Sun overhead 21 December Time goes ahead Time goes behind Sun does not rise on 21 Dec Sun does not rise on 21 June
Draw a red line along the equator (0 degrees latitude).
2. Draw a purple line along the Prime Meridian (0 degrees longitude).
3. In which ocean is the location 10 degrees S latitude, 75 degrees E longitude located? Mark it on the map with a blue "X" and write the name of the ocean.
4. In which ocean is the location 30 degrees N latitude, 60 degrees W longitude located? Mark it on the map with a blue "Y" and write the name of the ocean.
5. Mark the following cities on the map in red:
B. Beijing: 40°N, 116°E C. Cairo: 30°N, 31°E CT. Cape Town: 34°S, 18°E H. Hong Kong: 22°N, 114°E J. Jakarta: 6°S, 106°E LA. Los Angeles: 34°N, 118°W LI. Lima: 12°S, 77°W LO. London: 51°N, 0°W MC. Mexico City: 19°N, 99°W MO. Moscow: 55°N, 37°E MU. Mumbai: 19°N, 72°E NA. Nairobi: 1°S, 37°E NO. New Orleans: 30°N, 90°W NY. New York: 40°N, 74°W R, Rio de Janeiro: 23°S, 43°W SE. Seattle: 47°N, 122°W SY. Sydney: 34°S, 151°E TK. Tokyo: 35°N, 139°E T. Toronto: 43°N, 79°W
Deserts are found here And here
Sun hits at right angles and heat has less distance to reach land so is stronger Sun has further to travel to land, because of the curve of the Earth so it’s weaker and less hot Why? Therefore it gets hotter the closer you are to the equator
At 30 degrees north and south of the equator there are NO CLOUDS and so the full force of the sun’s rays can hit the earth….making it very hot!
What happens at night? At night time the clouds at the equator act like a giant blanket. They trap some of the heat that is leaving the earth and keep it nice and warm In the desert there is no blanket of clouds and so all of the heat from the earth simply escapes into the atmosphere. So it can get very cold in the desert at night. There have even been reports of frost found in the desert!! At 30 degrees north and south of the equator there are NO CLOUDS and so the full force of the sun’s rays can hit the earth….making it very hot! In the daytime…..?
Angle of the sun hitting the Earth , at low latitudes the sun is strongest and the temperature in the daytime is warmer
Lack of clouds due to high air pressure which prevents cloud formation, clouds would block out the sun reducing heat
Complete questions 2 a and b onto your sheet
Why are deserts hot? Insolation equals heat!
2A Answers – missing words
Places near the equator are hotter because the Insolation reaches the earth at right angles. This concentrates the insolation and causes the earth to heat up more quickly.
places away from the equator are colder because the sun’s rays hit the Earth at an angle. The rays have to travel a greater distance
Deserts are very because there are no at 30 degrees latitude to get in the way of the sun’s .
At night because there are no clouds all the heat into space and it gets very
At the equator there are lots of .
These prevent the full force of the rays from reaching the Earth keeping it .
hot clouds hot clouds rays rays cold cold clouds clouds suns suns Warm, warm
Why are deserts dry? It’s all about pressure! Air presses down on land , which brings fine weather as clouds do not form High pressure Low pressure Air rises from the land as it rises it cools, condenses into clouds and causes rain Rain
Hottest part of planet At 0 degrees it is hot and wet At 30 n and s it is hot and dry
Low pressure at equator High pressure high At 30 degrees north and south of equator the air sinks forming high pressure which brings dry fine weather At equator warm air is forced to rise as it does, it cools, condenses and forms clouds and you get rain
The air around the Earth is always on the move, both across the surface and up and down in the atmosphere.
No clouds so at night heat escapes to space Clouds keep heat in at night Deserts Rainforests Sun high in sky so hot Sun high in sky so hot No clouds (clear sky)= no rain Clouds form= rain High pressure Low pressure 30 DEGREES NORTH AND SOUTH Equator (0 DEGREES)
What to do
Complete the section 3 Why are deserts dry on your A3 sheet
* Complete a and b!
Question 3a answers Air presses down on land , which brings fine weather as clouds do not form High pressure Low pressure Air rises from the land as it rises it cools, condenses into clouds and causes rain Rain
Question 3 b -answers
LOW pressure is found at the equator which means the weather will be wet, humid and stay so throughout the day
HIGH pressure is found at 30 degrees north and south of the equator. This means that the weather will be very hot in the day, dry and colder at night due to lack of clouds keeping in the heat
Why are deserts found on the west of continents? North East trade winds South East trade winds South East trade winds North East trade winds equator
The Earth’s rotation pushes winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Between 30 degrees north and south of the equator we call these prevailing (most common) winds the north and south east trade winds.
These winds hit the east coasts first, and because they have come over the sea they are carrying moisture which means the east coast gets the rain. By the time the winds get into the centre the moisture has been used up. By the time the winds reach the west coast of continents they are very dry, so no rain falls.
The Sahara is the largest desert as the winds have to travel over the largest land mass on the way to the Sahara
Explain in your own words why deserts are found on the west coasts of continents
Why is the Atacama the driest desert in the world? Atlantic ocean Winds to South America blow from the Atlantic ocean to the Pacific ocean Pacific ocean So it rains along the Atlantic coast and inland Once it gets to the Andes mountains it is lacking moisture At the Andes air has to rise Andes Mountains
As it rises It cools, creating LOW pressure = clouds = rain. Mountains cause a rain shadow effect- behind them it does not rain By the time the air reaches the top of the mountains it has lost all of its moisture. As the air sinks down the other side of the mountains it warms up. = HIGH pressure = no clouds and no rain. But some animals & still plants survive there Atlantic ocean Pacific ocean
Label the diagram on the sheet (question 5) to explain why the Atacama is the driest desert
What have you learnt?
Name 2 deserts of the world
Deserts are hot because……………..
Deserts are dry because of pressure. What pressure makes deserts dry?
Why are deserts found on the west coast of continents?
Why is the Atacama the driest desert in the world?