1. Earth’s Materials and Processes-Part 2 Weathering, Erosion, and Deposition

2. The Changing Surface of the Earth
Weathering and Erosion work together to change Earth’s surface by wearing down and carrying away rock particles.
Weathering and Erosion continuously work to re-shape Earth’s surface.
The Principle of Uniformitarianism is used by Geologists to infer what processes shaped Earth’s surface. This principle states that the geologic processes that operate today, also operated in the past, and will in the future.

3. Weathering
Mechanical weathering occurs when rock is physically broken into smaller pieces. (Think PHYSICAL property).
Natural agents include freezing and thawing, release of pressure, plant growth, animal activity, and abrasion.
Chemical weathering occurs when rock is broken down as a result of chemical changes.
Agents include water, oxygen, carbon dioxide, living organisms, and acid rain.
Ex: Rust, Burning Fossil Fuels

4. Factors affecting Weathering Rates
Type of Rock: Rocks wear down slowly if they are made of minerals that do not dissolve easily.
Rock Permeability: Holes in the rock can allow water to enter and dissolve materials.
Climate: Average weather conditions, amount of moisture, freezing, thawing, temperatures, etc.

5. Erosion
Erosion is the process that moves weathered rock from its original location.
Agents include gravity, water, ice, and wind.
Moves material called sediment, which may consist of pieces of rock or soil, or the remnants of plants and animals.
Deposition occurs when the agents of erosion deposit sediment.

6. Forming Soil
Soil is the loose, weathered material on Earth’s surface in which plants grow.
It is a mixture of rock particles, minerals, decayed organic material, water, and air.
The main components come from bedrock, or the solid layer of rock beneath the soil.
The particles of rock in soil are classified by size as gravel, sand, silt, and clay.
The decayed organic material in soil is called humus, it contains nutrients plants need and helps to create space in soil that are later occupied by air and water.

8. Mass Movement Process by which gravity moves sediment downhill.
Can be caused by a natural disaster such as a flood, earthquake, or hurricane.
Different types of mass movement include landslides, mudflows, slumps, and creep.

10. Erosion by Wind
Wind can be a significant agent in shaping the land in areas where there are few plants to hold the soil in place.
Deflation is the process by which the wind removes surface materials
Abrasion occurs as particles move against exposed rock, and friction wears away the rock.

11. Deposition by Wind
Sand Dunes are a deposit of windblown sand, when wind meets an object, such as grass.
Loess is fine, wind-deposited sediment that occurs when the wind drops sediment that is finer than sand, but coarser than clay, from its source.

12. Erosion by Water
As water moves over land, it picks up and carries sediment. This moving water is called runoff.
Gravity causes runoff and sediment it carries to flow downhill. As runoff moves across the land, it flows together to form rills, gullies, and streams.

13. Stream Formation
As runoff travels, it forms tiny grooves in the soil called rills.
Many rills flow into one another to form a gully, or a large groove or channel in the soil that carries runoff after a rainstorm.
Gullies join to form a stream, or a channel along which water is continually flowing down a slope.
A tributary is a stream or river that flows into a larger river.

14. Water Erosion and Deposition Creates Landforms
Waterfalls erode soft rock, leaving a ledge made up of hard, slowly eroding rock.
A river usually flows over more gently sloping land, spreads out, and forms a wide river valley. The flat, wide area of land along a river is a flood plain.
A river often develops meanders where it flows through easily eroded rock or sediment. This is a loop-like bend in the course of a river.

16. Water Deposition
Deltas form when sediment is deposited where a river flows into an ocean or lake and builds up a landform.
An alluvial fan occurs when a stream flows out of a steep, narrow mountain valley, then suddenly becomes wider and shallower, then slows down and deposits sediment.

17. Groundwater and Earth’s Surface
Groundwater is the term geologists use for underground water.
Groundwater causes erosion by chemical weathering. In the atmosphere, rain water combines with carbon dioxide, forming carbonic acid, which can break down limestone.
Carbonic acid and limestone can result in deposition; as it drips from a cave’s roof, it forms stalactites and stalagmites.

19. Karst Topography
Landscape where the roof of a cave collapses due to limestone erosion.
Called a sinkhole.
This type of landscape is called Karst Topography.

20. Glaciers and Earth’s Surface
A glacier is any mass of ice that moves slowly over land.
Glaciers are part of the cryosphere.
A continental glacier is a glacier that covers much of a continent or a large island.
A valley glacier is a long, narrow glacier that forms when snow and ice build up over a mountain valley.

21. Glaciers and Earth’s Surface
As a glacier flows over land, it picks up rocks in a process called plucking.
The weight of the ice breaks rocks into fragments that freeze into the bottom of the glacier.
These rocks are carried with the glacier.
Leaves a jagged landscape.

22. Glaciers and Earth’s Surface
Abrasion occurs when the rocks remain embedded on the bottom and sides of the glacier, and are dragged along the land.
For glaciers, advancing, retreating, and eroding the land are slow events.
Although they move and work slowly, glaciers are a major force of erosion.

23. Glacial Deposition
As the glaciers melt, they deposit sediment eroded from the land.
The mixture of sediments that a glacier deposits directly on the surface is called till, which includes clay, silt, sand, and gravel.
The till deposited at the edges of a glacier form a ridge called a moraine.
Retreating or melting glaciers create features called kettles, or steep sided depressions that form when a chunk of ice is left in glacial till.

25. Waves and Earth’s Surface
The energy from most waves comes from the wind.
Stronger wind creates larger waves.
The friction between the wave and the ocean floor slows the wave.
The water breaks powerfully on the shore. This forward-moving water provides the force that changes the land along the shoreline.

26. Waves and Erosion
Waves shape the coast through weathering and erosion by breaking down rock and moving sand and other sediments.
Waves break away rocks by abrasion, or enlarging small cracks in rocks, causing pieces of them to break off.
As a wave approaches shallow water, it picks up and carries sediment. When it hits land, the sediment wears away rock.

27. Landforms by Wave Erosion
Waves erode softer rock first.
Can erode a hollow notch in the rock called a sea cave.
Can erode the base of a cliff until collapse.
A sea arch forms when waves erode a layer of softer rock that underlies a pillar of harder rocks.

28. Wave Deposition
Deposition occurs when waves lose energy and slow down.
A beach is an area of wave-washed sediment along the coast.
As waves hit the beach repeatedly, some sediment gets carried along the beach by the current, in a process called longshore drift.
Longshore drift can create sandbars and create barrier islands.