Weathering, Erosion, & Deposition The Wearing Down and Building Up of Earth

T/F Wind, water, ice, and gravity continually shape Earth’s surface. Different sizes of sediment tend to mix when being moved by water. A beach is a landform that does not change over time. Windblown sediment can cut and polish exposed rock surfaces. Landslides are a natural process that cannot be influenced by human activities. A glacier leaves behind a smooth land as it moves through an area.

Weathering, Erosion, Deposition, and Landscapes Weathering – the breakdown of rocks into smaller pieces, called sediments. Erosion – the process where the sediments are transported by wind, gravity, glaciers, man, and running water. Deposition – the process whereby these sediments are released by their transporting agents (dropped). Weathering breaks down the rocks, erosion moves the particles, and deposition drops the sediments in another location.

There are two primary types of weathering: Chemical and Physical 1. Physical Weathering – the breakdown of rocks and minerals into smaller pieces without a change in chemical composition. Root/Plant Wedging/Action Ice/Frost Wedging/Action Exfoliation and Abrasion are also types of physical weathering.

2. Chemical Weathering – the breakdown of rocks and minerals into smaller pieces by chemical action. The rocks breaks down at the same time as it changes chemical composition. The end result is different from the original rock. There are 3 types of chemical weathering: 1. Oxidation – oxygen combines with the elements in the rock and it reacts. This the scientific name for rust. 2. Hydration – water can dissolve away many earth materials, including certain rocks. 3. Carbonation – carbon dioxide dissolves in water to form carbonic acid. This makes acid rain which chemically weathers (dissolves) rocks. Other acids also combine with water to make acid rain.

Erosion (transport) There are 5 main agents of erosion: *Running Water* Glaciers Wind Gravity Man Weathering has to happen before erosion. The rocks have to be broken into smaller sediments before they can be eroded away. Wind Erosion Glacier

WATER EROSION Water sources such as rivers, streams, ocean tides, and runoff can move rock particles away....

Water Erosion-Rivers Rivers and streams carry sediment. As the sediment moves mechanical weathering occurs. Through water erosion, rivers create waterfalls, flood plains, and valleys.

Water Erosion-Waves Waves- waves shape the coasts by transporting sand. While the sand is moved, mechanical weathering occurs. Waves create sea stacks, caves, arch, and wave-cut cliffs.

Erosion by Runoff As water from precipitation (rain, snow, etc.) moves over the land, it carries particles with it. The moving water is called runoff. Runoff creates rills and gullies.

Groundwater Erosion (CAVES) Rainwater absorbs carbon dioxide (CO2) in the air as it falls. The CO2 combines with water to form carbonic acid. The slightly acidic water sinks into the ground and moves through pore spaces in soil and cracks and fractures in rock. Carbonic acid is especially good at dissolving the rock limestone.

Caves continued Cave Formation Working slowly over many years, groundwater travels along small cracks. The water dissolves and carries away the solid rock, gradually enlarging the cracks.

Groundwater carries dissolved minerals in solution. The minerals may then be deposited, for example, as stalagmites or stalactites. Stalactites form as calcium carbonate drips from the ceiling of a cave, forming beautiful icicle-like formations (c for ceiling.) Stalagmites form as calcium carbonate drips from the ceiling to the floor of a cave and then grow upwards. (g for ground) If a stalactite and stalagmite join together, they form a column.

WIND EROSION Sometimes the wind can move rock particles away: this can lead to dust storms!

WIND EROSION Wind Erosion creates dust storms, hoodoos, and arches.

Ice Erosion As a glacier flows over the land, it picks up rocks in a process called plucking.

Ice Erosion Ice erosion creates: U-shaped valleys, glacial lakes, moraines, drumlins, and kettle lakes.

Mass Wasting – downhill movement of material due to gravity Erosion Rates of MW can range from very slow to very fast. Deposition Material eroded during a mass wasting event will continue to move and eventually deposits when it reaches a stable location

Erosion by Gravity Gravity causes sediment to move downhill. It creates: landslides, mudflows, and creeps. Creep - slow downslope movement of particles that occurs on every slope covered with loose, weathered material

Deposition Deposition is the process in which sediment laid down in new locations. Caused by water, wind, ice, and gravity

Deposition Wind Sand Dune Water *Waves *River *Beaches *Delta Ice Type of Deposition Creates Picture Wind Sand Dune   Water *Waves *River *Beaches *Delta Ice Moraine Gravity Landslide, Slump, Creep