UNIT 18 SURFACE OF THE EARTH

What features are found on the Earth’s surface?

1. Continents and Islands Continents – 7 large masses of land

- made up of Africa, Antartica,

Asia, Australia, Europe,

North America and South America

- largest continent is Asia Islands – thousands of small land masses

surrounded by water

The seven continents

2. Oceans, seas, lakes and rivers 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 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 EverestMarianas 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

What can change the Earth’s surface?1. Rain

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 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 can pick up small particles of sand, soil and

rocks abrasion by wind particles change shape of

rocks

4. Sunlight 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 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 occur over time 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 rocksErosion of soil

2. Rapid process

require a very short time for changes to be observable

Include:

LANDSLIDES - movement of rocks down a

slope

VOLCANIC ERUPTIONS AND EARTHQUAKES

slow plate movements can cause volcanic formation and earthquakes

How do human activities change the Earth’s surface?

1. Industrialization Factories, power plants and houses Dams Logging Mining Roads and bridges

dam

logging

mining

bridge

2. Farming

greater demand for food more land required for better yielding crops

3. Land reclamation

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 Do not cut trees unnecessarily Grow trees and plants on exposed soil Keep soil damp during hot weather to lessen

erosion by wind

2. Preventing landslides

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

place breakwaters, rocks and concrete along rivers and river banks

4. Preventing floods

build a strong, thick wall (dyke) along the river

Sources:

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