1. UNIT 18 SURFACE OF THE EARTH

2. 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

3. The seven continents

4. 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

5. 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 Everest Marianas trench

6. 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

7. 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

8. 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

9. 3. Wind can pick up small particles of sand, soil and rocks abrasion by wind particles change shape of rocks

10. 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 expansionFrost action

11. 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

12. 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

13. Weathering of rocks Erosion of soil

14. 2. Rapid process require a very short time for changes to be observable Include: LANDSLIDES - movement of rocks down a slope

15. VOLCANIC ERUPTIONS AND EARTHQUAKES slow plate movements can cause volcanic formation and earthquakes

16. How do human activities change the Earth’s surface? 1. Industrialization Factories, power plants and houses Dams Logging Mining Roads and bridges

17. dam logging mining bridge

18. 2. Farming greater demand for food more land required for better yielding crops

19. 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

20. 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

21. 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

22. 3. Preventing abrasion place breakwaters, rocks and concrete along rivers and river banks

23. 4. Preventing floods build a strong, thick wall (dyke) along the river

24. 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