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 Large 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