Earths Features of Earth is covered by water
Earth’s Features
• ¾ of Earth is covered by water. –Most of the water is in oceans. • Earth has 7 great areas of land called continents. –North America (where we live)
Landforms • Mountain – tallest; has steep sides and pointed top • Valley – low land between hills or mountains. • Canyon – deep valley with steep sides • Plain – land that is wide and flat • Plateau – steep sides and a flat top; higher than land around it. • Coast - land that borders the ocean • Peninsula – land surrounded by water on 3 sides • Island – land with water all around it
Water Features • Ocean – large bodies of salt water • Lake – water that is surrounded by land; can be fresh or salt water • River – large body of moving fresh water • Glacier – a large, slow moving, block of ice
Land Features in the Ocean • Ocean Floor – Land below the ocean. • Continental Shelf – a huge plateau that lies under the ocean at the edge of a continent. • Abyssal Plain – wide and flat, stretches thousands of kilometers across the ocean. • Trench – a canyon on the ocean floor.
Layers of the Earth • Crust – The outermost layer – Made up of the continents and the ocean floor – The thinnest and coolest layer • Mantle – Layer below the crust – Part solid rock – Part nearly melted rock that is soft and flows (like putty) • Core – Deepest and hottest layer of Earth – Outer Core – Melted Rock – Inner Core – Solid Rock
Sudden Changes to Earth
Earthquakes • A sudden movement of the rocks that make up the Earth’s crust • The ground shakes or vibrates. • Some earthquakes are very weak and aren’t even noticed while others are very strong. –Some can crack roads or even cause mountains to fall!
Volcanoes • A mountain that builds up around an opening in Earth’s crust – Melted rock (magma) moves through a large crack in the crust and flows onto land. – When it flows onto land it is called lava. – If the lava is forced out in an explosion a large part of the mountains is blown away • Materials from volcanoes can cause a lot of damage to buildings and living things.
Landslides • The rapid movement of rocks and soil down a hill. • Caused by gravity. • Can change a hill or mountain very quickly.
Floods • Water that flows over land that is usually dry. • Can be caused by heavy rains and melting snow. • Flood waters are very strong.
Weathering, Erosion, and Deposition
What is Weathering? • The breaking down of rocks into smaller pieces is called weathering. • Happens so slowly you cannot see it. • Can take millions of years.
What causes weathering? • Running water and Wind – Pick up small rocks that scrape against other rocks – The scraping slowly wears away rocks. • Rain and Melting Snow – Enter cracks in rocks – Water freezes and expands widening the crack before thawing and becoming liquid again – Over time, repeated freezing and thawing breaks rocks apart.
What causes weathering? • Living Things –Plants grow in the cracks of rocks • The roots eventually split rocks apart –Animals dig in the ground • They uncover buried rocks • The uncovered rocks can then begin to weather.
What is Erosion? • The movement of weathered rock • Moving water, wind, and glaciers and gravity all cause erosion • Happens very slowly • Weathering and erosion work together to change the land
Moving Water and Wind • Moving water and wind picks up rocks and sand • The rocks and sand may be carried far away and dropped in new places. • Deposition – the dropping off of weathered rock.
Glaciers • While moving a glacier picks up and carries rocks of all sizes. • The ice at the bottom of the glacier freezes onto rocks and tears them out of the ground • Can move rocks the size of a house. • As glacier melts, rocks are dropped off in a new place.
People change the Land • Small Changes – Digging a hole in your backyard • Large Changes – Trees cut down to build roads, stores, and homes • If trees are not replanted, soil can wash away – Ponds and swamps are drained • Dry soil left behind can blow away – Land is dug up to reach valuable rocks
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