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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 Continents – 7 large masses of land - made up of Africa, Antartica, Asia, Australia, Europe,

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UNIT 18 SURFACE OF THE EARTH

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  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) Marianas trench Mount Everest

  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 expansion Frost 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 mining bridge logging

  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

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