Weathering & Erosion Chapter 4 Lesson 3 Page 192

What is weathering? Answer: A As rain falls on the cliffs of the Palisades in New Jersey, water trickles into the cracks and freezes. The ice will push the cracks further apart and parts of the rock will break off This is just one example of Weathering Weathering is the process through which rocks or other materials are broken down Weathering is considered a DESTRUCTIVE process Answer: A

What is weathering? Physical Weathering This is caused by pushing, pulling, rubbing, or temperature changes Water in the cracks of rock freezing Trees and other plants can also grow into the cracks on a cliff and as their roots grow they can push the walls of the cracks further apart. Gravity can pull pieces of rocks down a slope. As the rocks roll down and bump into each other Wind can blow on exposed rocks. The winds pick up small particles of sand or dirt and rub against the rock (like sandpaper) Water- as rocks are carried along in moving water they may bump each other. This wears away the surface of the rock

Chemical Weathering Answer: D This occurs when chemicals break down rocks Chemicals in groundwater break down underground rock and caves form Acid rain breaks down stone or metal (like in statues) Answer: D

What is erosion? The process through which weathered rock is moved from one place to another Land can be eroded by gravity, glaciers, running water, waves, or wind Erosion is a DESTRUCTIVE PROCESS Gravity Rocks and soil on a slope can be loosened by the pull of gravity and eventually brought down the slope. Mudslides occur when rain that can no longer soak into the ground mix with the soil and get pulled down by gravity Landslides are the movement of a large amount of rock and soil down a slope

What is erosion? Glaciers A large mass of slowly flowing ice Glaciers form in cold areas where snow piles up and freezes As the glacier moves, it carries away weathered pieces of rock The bits of rock wear away the ground at the beginning of the glacier, forming a steep bowl-shaped hollow called a cirque A valley that had a sharp V-shape before a glacier came through will not have a U-shape, with a flatter bottom and sides

Answer= A Glaciers are responsible for carving out U-shaped valleys

What is deposition The process by which eroded materials are dropped off in another place This is a CONSTRUCTIVE PROCESS When a glacier erodes dirt and rock, the eroded materials are pushed in front of it. When the glacier starts to shrink, the eroded materials are left behind Erosion and deposition can work together to change the shape of Earth’s surface

Erosion & Deposition by running water As water flows down hills, it can wash away soil and erode rock. The water, soil, and rocks will eventually flow into a larger body of water, such as a river Rivers with fast-moving water tend to follow straight paths and have deeper channels and steeper banks. Rivers with slow-moving water tend to follow looping paths and have shallow channels and low banks More deposition occurs in slow-moving rather than fast-moving water Meanders, or gentle loops, sometimes form in rivers with slow moving water. Water moves slowly around the inside of a meander. Particles of soil and rock that are carried along in water are called sediment.

Erosion & Deposition by running water As sediment is being carried down stream it can be deposited into different areas and form other pieces of a land A river delta is a landform that is formed at the mouth of a river, where the river flows into an ocean, sea, estuary, lake, or reservoir The Mississippi River Delta has been formed by the Mississippi River

Erosion and Deposition by waves Waves often hit beaches at an angle or curve as they move into shallower water The shoreline is eroded by the waves because they move rocks and sand further down the beach or to the side When waves wash sand off beaches, they may be deposited in the water rather than back on the beach Sandbar is a strip of land that forms from deposited sand

SANDBAR

Erosion and deposition by wind Wind can wear away rocks, smoothing them out. Wind also can move sand or sediment from one place to another When the winds slow down, the sand and soil are deposited

How are shorelines changed? Running Water Water runs over the ground into streams and rivers. Sometimes, water enters a river faster than a river can carry it away. When water collects on land that is normally dry, it is a flood Flooding occurs when water from a body of water overflows banks or beaches Floodplains are places that are easily flooded when river water rises Natural wetlands can soak up water and reduce the chances of a flood. Draining wetlands or cutting down plants along a riverbank may make floods more likely Floods can erode the shoreline of a body of water and change its shape or course Flooding can be a positive because the soil becomes rich in nutrients

How are shorelines changed? Waves When large sandbars stretch for hundreds of kilometers along a coastline, they are called barrier islands Waves hit barrier islands first and erode the barrier islands rather than the coastline beaches Wind Some coastal areas have one or more sets of dunes running along the shoreline directly inland from the beach A dune forms when wind erodes sand and deposits it along the back of the beach Dunes form in the direction that the wind usually blows. They protect areas farther inland from the large waves that can occur during storms

How can shorelines be protected A shoreline may be damaged when more sand is being eroded than deposited People can protect river shorelines by changed the speed or direction of running water Dams can control the speed of the flour of water in a river Canals or channels can be dug to carry away water that would cause flooding Fences and grasses help keep sand dunes from being eroded by wind