1. Hot Deserts
Revision

2. Location of World Deserts.

3. Location of World Deserts.

4. Climate Graph

5. Explaining Climate Data
Why do the temperatures vary between day and night?

6. Insolation Weathering: Exfoliation
Insolation weathering can cause Exfoliation.
Similar to Block Disintegration, the heat from the Sun causes rocks to heat up and cool down at different rates.
This puts strain on the rock and leads to layers of rock peeling off.

7. Insolation Weathering: Freeze thaw
Freeze thaw occurs when the temperatures fall below freezing in the night.
Moisture collects in the cracks in the rock. When the water freezes it expands and widens the crack until eventually the rock splits.

8. Salt Weathering Salt Weathering is similar to freeze thaw.
Moisture draws salt out of the rocks and then evaporates leaving behind the salt.
The salt expands as it crystalizes and the rock splits.

9. Erosion Erosion is the wearing away of rocks.
In a desert the main agent of erosion is the wind and occasionally water.
Deflation is the gradual removal of sand and dust to leave a flat surface or hollow in the rock.

10. Erosion
Abrasion is the sandblasting effect of sand particles carried in the wind.
The sand in the wind erodes the rock, sometimes into unusual shapes by wearing it away by the sand particles hitting the rock.

11. Deposition
Deposition is the laying down of material that has been eroded
Wind carries fine particles of sand and deposits them as sand dunes. If the wind continues to blow, it moves the sand and changes the shape of the dunes.
During a flash flood, rivers remove large amounts of material and deposit it further along the valley.

12. A Mushroom rock or a Rock Pedestal
Rock Pedestal is made up of alternating layers of resistant and less resistant rock
Wind blown sand has shaped the rock through abrasion
Resistant Rock is worn away more slowly
Abrasion greatest nearer base of rock where wind carries more sand
Less resistant rock – eroded more easily

13. Zeugen
Horizontal layers of resistant rock on top of less resistant rock.
The resistant rock must have cracks and joints in it.
The joints are made wide by freeze thaw at night when the temperatures drop.
The wind gets into the cracks in the resistant rock and reaches the less resistant rock.
Particles of the resistant rock break are eroded off by the wind.
The wind then carries these particles to the less resistant rock.
The less resistant rock is then worn away by deflation and abrasion.
Because the less resistant rock is eroded more easily the ridges are narrow at the base and have wider, flatter tops.

14. Features of Deposition: Sand Dunes
Direction of prevailing wind
Sand is deposited on steep sloping leeward side
Sand particles blow up gently sloping windward side
A sand dune forms around an obstacle on the ground such as a rock, a bush or an abandoned vehicle.
The wind hits the obstacle and looses energy and drops the sand it is carrying.
The sand dune continues to grow and moves in the direction of the prevailing wind.

15. How this cactus has adapted to survive in the desert.
Spike rather than leaves
How this cactus has adapted to survive in the desert.
Thick, waxy skin
Large, fleshy stems
White upper surface
Extensive root system

16. Flowering plants - Shrubs
Seeds lie dormant for years
They flower with a few days
Plants grow quickly after rain
How these plants have adapted to survive in the desert.

17. How this Camel has adapted to survive in the desert.
Two rows of long eyelashes
Nostrils can be closed
So doesn’t need to eat so often
Fat stored in humps
Thick woolly fur
Tough, leathery knee pads
Long, powerful legs
Can drink up to 50 litres of water in a few minutes
So it will not sink into sand
Broad, flat hooves