Transcript unit 18 surface of the earth

UNIT 18
SURFACE OF THE EARTH
What features are found on the
Earth’s surface?
1. Continents and Islands
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Continents – 7 large masses of land
- made up of Africa, Antartica,
Asia, Australia, Europe,
North America and South America
- largest continent is Asia
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Islands – thousands of small land masses
surrounded by water
The seven continents
2. Oceans, seas, lakes and rivers
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70% of the Earth’s surface is covered by water
surrounding the continents and islands
Pacific ocean is the largest and deepest ocean
3. Mountains and hills
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Some mountain ranges are found on the ocean floor.
Highest point on Earth is Mt. Everest (8848 m above
sea level) in the Himalayas mountain ranges
Lowest point on Earth is the Mariana Trench
in the Pacific Ocean (about 11033 m below sea level)
Mount Everest
Marianas trench
4. Other features
Plains
 Volcanoes
 Valleys
 Desert – make up 1/3 of the Earth’s land surface
Classified into:
Hot desert – high temperature all year long
Temperate desert – hot summers and freezing
cold winters
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What can change the Earth’s surface?
1. Rain
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washes away and exposes soil resulting in
barren land
acid rain (formed when sulphur dioxide and
oxides of nitrogen dissolve in rainwater)
removes nutrients from soil, kill aquatic
organisms, corrodes and damages buildings
2. Running water
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sediments hit against rocks on rivers and grind
against the riverbed and riverbanks
rocks loosen and break into pieces by physical
grinding (abrasion)
flow of water carries loosened materials away
forming caves and valleys overtime
3. Wind
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can pick up small particles of sand, soil and
rocks
abrasion by wind particles change shape of
rocks
4. Sunlight
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Thermal expansion – expansion of rocks in the day
and contraction at night
- common in areas with large temperature change
such as the desert
Frost action – water trapped in rocks may freeze to
become ice and expand causing cracks to enlarge
Thermal expansion
Frost action
5. Tidal waves
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waves crash onto shores and against cliffs
sediments hit and scrape against land surfaces
loosening and smoothening materials
outgoing waves carry loosened materials away
What processes change the Earth’s
surface?
1. Slow processes
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occur over time
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Include:
WEATHERING – physical and chemical break
down of rocks and other land structures
Agents are: rain, water, sunlight, tidal waves,
wind
EROSION – washing away of soil and rocks
Agents are: running water, tidal waves, rain,
wind
Weathering of rocks
Erosion of soil
2. Rapid process
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require a very short time for changes to be
observable
Include:
LANDSLIDES - movement of rocks down a
slope
VOLCANIC ERUPTIONS AND EARTHQUAKES
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slow plate movements can cause volcanic
formation and earthquakes
How do human activities change the
Earth’s surface?
1. Industrialization
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Factories, power plants and houses
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Dams
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Logging
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Mining
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Roads and bridges
dam
mining
bridge
logging
2. Farming
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greater demand for food
more land required for better yielding crops
3. Land reclamation
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rocks and other Earth materials are excavated
from hills to reclaim land from the sea
needed to build housing for expanding population
How can we prevent the destruction
of the Earth?
1. Preventing erosion
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Do not cut trees unnecessarily
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Grow trees and plants on exposed soil
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Keep soil damp during hot weather to lessen
erosion by wind
2. Preventing landslides
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regrow trees and plants on barren slopes
do not cut down trees unnecessarily
place a wire mesh over rocks and exposed soil
3. Preventing abrasion
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place breakwaters, rocks and concrete along
rivers and river banks
4. Preventing floods
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build a strong, thick wall (dyke) along the river
Sources:
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http://pangaeanetwork.org/images/pangaea_map.png
http://www.oceania-maps.com/layout/pacific-ocean.gif
http://www.ianbrookesphotography.co.uk/images/20081201221946_pb145581.jpg
http://glassbox-design.com/wp-content/uploads/2009/01/mariana-trench.jpg
http://www.ux1.eiu.edu/~cfjps/1300/heaved.jpg
http://web.uct.ac.za/depts/geolsci/dlr/ant/Scan514.jpg
http://upload.wikimedia.org/wikipedia/commons/4/41/India_Farming.jpg
BBC world challenge links
http://www.theworldchallenge.co.uk/2010-finalists-project08.php
http://www.theworldchallenge.co.uk/2005-winner.php