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True or False: The Earth’s surface has stayed the same for thousands of years. The Earth’s surface is always changing! Weathering is the wearing down of rocks on Earth’s surface by wind, water, and ice. Here are some ways that weathering can occur… 1. Cool nights and hot days can cause rocks to crack open. 2. Water may seep into the cracks of rocks. If the water freezes, then the water expands, causing the cracks to be larger and breaks the rocks apart. When the water melts and freezes again, it’s starts the whole process over again. 3. Rain and running water can also break down rock into smaller particles. http://www.pbs.org/wgbh/nova/earth/how-caves-form.html Running water smoothes rock creating round stones and pebbles. You can find these types of rock in streams and rivers. 4. Wind carrying sand and other particles can also wear down rocks over time Running water Rain weathering Running water and wind Wind Rocks in a stream or river that have been weathered What are some types of weathering that can wear down rock? Why do you think this process is called “WEATHERING”? Can you think of any examples of “weathering” that you can see in your own community? Erosion- is the process by which weathered rock is moved away by wind, water, or ice to a new location. As the wind blows, it picks up small particles of sand/sediment and blasts large rocks with the abrasive particles, cutting and shaping the rock. Wind is one of the most active agents of erosion, especially in beaches, fields, and deserts. Loose materials on the ground in these areas are easily picked up by wind and can land anywhere. Water flowing in streams and rivers can also break up rock and soil. The water in the streams and rivers then carry these materials – known as sediment – to another location. http://www.bbc.co.uk/schools/riversandcoasts/coasts/change_coast/index.shtml Sediment is sand pebbles, and other particles moved by erosion and left in a new location A fast-flowing river can gradually cut through layers of rock, even creating a beautiful canyon, like the Grand Canyon. Canyon- is a deep narrow valley with steep sides often with a stream running through it. The eroding rock has been carried by the river to a new location. Examples of Erosion http://www.classzone.com/books/earth_science/terc/con tent/visualizations/es1205/es1205page01.cfm?chapter_no= visualization Glaciers are rivers of ice. They form in places where there are very cold winters and cool summers. The snow that falls in the winter does not melt during the summer. Instead, the snow turns into ice. New snow then falls on top of this ice. As the layers of snow build up, the weight of the snow increases, which then pushes on the layers below causing glaciers. Glaciers move very slow, and as they move, they scrape the Earth’s surface. Glaciers pick up loose rock, they can dig holes, wear down mountains, and move rock and soil. Glaciers can move millions of tons of material, including boulders. To reduce soil erosion from water, wind, and rain, farmers often plant trees, crops, or grass. The roots of the plant help hold the soil together against wind and rain. Farmers also plow the land on hills in horizontal rows to prevent fast-running rain water from falling straight downwards and washing away topsoil. What is a glacier? Life of a Glacier http://www.pbs.org/wgbh/nova/vinson/glac-flash.html How do glaciers cause erosion? What examples of erosion can you find in your own community? Examples of Erosion http://www.classzone.com/books/earth_science/terc/con tent/visualizations/es1205/es1205page01.cfm?chapter_no= visualization Deposition- is the process by which the new rocks, soil, and other sediment moved by erosion are left or deposited in a new place. Dunes are hills of sand most commonly found on beaches and in dry inland areas where lakes once existed. Winds blow the sand, creating hills with crests or ridges. Deserts, like the Sahara in North Africa have giant dunes made of wind-blown sand. Some dunes have been known to move such as 50 feet a year. Waves carry sand and other sediment to the shoreline, where they are deposited. This helps to create the many beautiful beaches found throughout the world. Hurricanes can also destroy the beaches carrying sediment to other locations and depositing them elsewhere. Delta- is a area that forms where a river flows into an ocean, sea, or lake. The river carries soil and other sediment. Once the river reaches the ocean or sea, its current stops. The sediment it is carrying is deposited at its mouth. This causes the delta to gradually build up, extending the land in a typical triangle shape. Sometimes, spring rains cause a river, creek, or stream to flood the area around it. When this occurs, the river leaves behind a layer of mud and other sediments. Gradually, these build up the floor of the flood plain. The flood will leave deposits of mud on the ground when it retreats. A glacial Moraine is material moved by a glacier and then left when the glacier retreats. It consists of the rocks, gravel, sand, and soil scraped by the glacier form the Earth’s surface. This material may have been carried by the glacier on its surface or underneath. Earth’s surface features are always changing. There are 3 important processes that SLOWLY change Earth’s surface features: 1. Weathering 2. Erosion 3. Deposition These processes are caused by the actions of water, wind, and ice. Weathering- is the wearing down of rocks on the Earth’s surface by wind, water, and ice. Weathering can be caused by water or ice seeping into the cracks in rocks. o Over time these cracks expand. o The water in the cracks then freezes and eventually, the rock breaks open. Rain and running water also help to break down rocks into smaller particles. Erosion- is the process in which rock, soil, and sand are broken down and moved away. Wind- can wear down rock and blow away sand and soil. Water- Streams and rivers break up rocks and soil and carry then to a different location. Ice- Glaciers cause erosion by scraping the ground along its path. Deposition- is the processes by which rocks, soil, and other sediment are deposited in new places. Dunes- Hills of sand found in dry inland areas. Beach- Area of shoreline where waves have deposited sand and sediment from the ocean. Deltas- Area formed by sediment where a river flow into an ocean, sea, or lake. Flood Plain- Area built by layers of mud and sediment from a flooding river. Glacial Moraine- Material left when a glacier retreats.