Weathering and Erosion

Oxbow lake

"bean" shaped lake

How is an oxbow lake formed?

As a river curves, the water traveling on the inside of the curve slows down which causes the river to deposit sediment. The water on the outside of the curve travels faster causing the river to weather the outer bank. Over time, this causes the meanders to become more exaggerated and some some cases the meander gets cut off from the rest of the river which produces a "bean" shaped lake

Graded Bedding

As a river or stream enters a lake or pond, the water speed and energy decreases causing the sediments to be deposited. The sediments are deposited in the order of largest particles first (bottom) to the tiniest particles (top).

How do caves form?

Carbon dioxide mixes with water to form a weak acid called Carbonic acid (same acid that is found in carbonated drinks). This acid reacts with rocks that have the mineral Calcite (like Limestone and Marble). The reaction that occurs causes the rock to appear like it's dissolving

Water(weathering)

Certain minerals react when in contact with_____. This forms some weaker minerals that are more susceptible to erosion. For example, the mineral feldspar reacts with ______ to form clay minerals.

Water, slope, vegetation, tectonic activity

Factors that cause erosion

Old stream

Flows smoothly through a floodplain it has carved

Mature stream

Flows smoothly through the valley. Erodes more on the sides. Forms meanders & oxbow lakes. Carves a flat, broad valley floor called a floodplain.

Young river

Flows swiftly through a steep valley. May have rapids & waterfalls. Erodes the bottom faster than the sides. "V" shaped valleys

U-shaped valley

Gravity pulls on these glaciers causing them to slowly move downhill. The sharp ice grinds and cuts into the surrounding rock as the glacier moves forming a smoother_____

snow accumulates in these places, it builds up layers. The weight of the snow compresses the layers of snow turning it into heavy ice

How are glaciers formed?

bottom-most layer becomes flexible & plastic-like

How do glaciers move?

Aquifer

Large areas of porous rock and soil collect and store this groundwater in areas. nonrenewable resource

Biochemical weathering

Plants & lichens can release chemicals, like acid, to help them grow through rocks

Atmospheric oxygen

Some gases in the air and the soil will mix with water to form an acid. Some of these acids are strong and others are weak, but most of these acids will react to certain minerals.

Changes in temperature and pressure

Swings in temperature and pressure will cause the rock to become weaker. This will lead the rock to cracking and then breaking apart. Rocks expand when heated and contract when cooled. Rocks expand under lower pressure than when they are in higher pressure.

Abrasion

The flow of water or air over rocks can slowly break down the rock due to friction. This will cause the rocks to become rounded and smooth. The faster the flow of water/air, the faster the weathering will occur

Mechanical weathering

The process of breaking down rocks and minerals into smaller pieces by physical force without changing its composition

Salt crystal weathering

The water in salty solutions will evaporate quickly in dry, hot environments. When the water evaporates, it leaves behind the salts in the rock pores. Salt expands when heated. This will cause the rock to break into pieces over time.

Water(erosion)

Too much ____ causes the the soil to become weak leaving it more susceptible to gravity, thus collapsing

Frost wedging

Water enters cracks in the rock and then freezes. When water freezes it expands causing the crack to get bigger. If this happens over and over again, the rock will eventually break apart. This also explains how potholes in roads form.

Uneven weathering on river bed causes what two things to form

Waterfalls and whitewater rapids

at tops of mountains or covering extremely cold landmasses

Where are glaciers found?

Mudflows

a large amount of rock and sediment mixed with water flows down a mountain

Rill erosion

a small stream forms during a heavy rain carrying away soil creating a channel

Surface area

as rocks are broken down into smaller pieces, it also increases the amount of ______ that is available to be weathered

Bedrock

base layer/horizon of soil

Meander

bends or loops in the river

Moraine

broken down rock the glacier accumulates

How is acid rain formed?

certain sulfur and nitrogen gases combine with water in the air. The Sulfuric acid that is formed can be a very strong acid that can weather away rocks, buildings, and statues over time, not to mention harm living things

Factors that affect rate of weathering

climate, rock composition, surface area

Humus

dark organic material in the topsoil, is rich in nutrients and is essential to plant life

Mass Wasting

form of erosion resulting in the downhill movement of large amounts of rock and sediment due to the force of gravity

Delta

form when rivers flow into large bodies of water like oceans and lakes. As the river enters the ocean/lake, the water flow drastically slows down resulting in the sediments being deposited at the mouth. These sediments build-up over time creating a "D-shaped" or triangle-shaped area of fertile land

Floodplain

land between valley walls

Gully erosion

large amounts of soil & sediment that are removed by heavy rains forming a gully

Watershed

large areas of land that collect precipitation and surface runoff, each one has a major river that the water flows into and its boundaries are defined by higher land areas like mountains

Rivers

large bodies of water that flows into an ocean, lake, or another river.

Landslides

large mass of soil or rock slides down a steep slope. They can be triggered by wet conditions or volcanic eruptions

Horizons

layers of soil

Slumping

loose soil becomes wet and slides. Usually happens after a period of very heavy rainfall

Tectonic activity

movement of the ground, particularly earthquakes, can bend, buckle, and crack the rock apart thereby exposing more of the rock to weathering and erosion. The stress of the movement also weakens the rock.

Water cycle

natural processes that water undergoes due to solar energy providing heat energy and by driving weather systems

Evaporation

occurs when liquid water absorbs enough energy to change it from a liquid to a gas (water vapor)

Condensation

occurs when the gas form of water (water vapor) in the atmosphere loses energy and therefore changes back into liquid water. However, in order for the water to become a liquid it requires a solid like dust & pollution particles to collect on

Runoff

occurs when the precipitation cannot be absorbed by the ground. This flows over land and downhill until it reaches a body of water

Biological factors

plant roots, burrowing animals, human activities

When do pores in plants open?

pores open when plants are taking in Carbon dioxide from the atmosphere and as a result, water and Oxygen escape. The water then evaporates

Deposition

process of ______ sediment after it has been moved by water, wind, ice, or gravity

Weathering

process of breaking down rocks and minerals

Erosion

process of moving rocks & sediment by wind, water, ice, and gravity

V

rivers that flow through mountains cut downward into the channel creating__shaped valleys

Till

rock deposited when glacier melts

Rockfalls

rocks that are part of a cliff or rocky overhang have become weathered to the point that gravity pulls the rock down

Vegetation

roots of plants and trees (especially grasses) grip the soil so that less of it can be washed away, blown away, or carried away. The more plants in an area, the better protected the soil is from erosion

Stream erosion

sediments are picked up from the bottom & sides of the stream bed by a flowing stream

Sheet erosion

sheets of water flowing across land carrying away sediments

Streams

small rivers

Topsoil

surface horizon of soil, contains weathered rock & minerals, organic material, water, & air

Channel

the path that a river or stream flows

Chemical Weathering

the process of breaking down rocks and minerals through chemical reactions. This results in the rocks and minerals changing their chemical composition.

Transpiration

the process through which plants lose water through tiny pores in their leaves

Slope

the steeper the ___, the more susceptible the soil/rock is to erode/fall away

Climate

the temperature and amount of water in an area will affect how much and what type of weathering will occur. Colder _____ experience more mechanical weathering (ice wedging & burrowing animals). Warm, moist ______ experience more chemical weathering (water & acids).

Rock composition

the types of minerals that make up rocks will determine the rate of weathering. Some minerals are more resistant to certain forms of weathering (quartz in Granite), while other minerals are more susceptible to weathering (Calcite in Limestone)

Precipitation

water that falls from the atmosphere (clouds) in the form of rain, sleet, snow, or hail.

Agents of chemical weathering

water, acids, atmospheric oxygen, biochemical weathering