(rain or shine, it always effects rocks the same way)

Get it, weather, get it…..

We Have Seen Weathering and Erosion Before ….. Here is a Recap

What is Weathering?

• Weathering is the process that breaks down rock and other substances at earth’s surface.

•:Almost anything in the environment can effect weathering. Some include

Heat

Cold

Water

Ice

Oxygen

Carbon Dioxide

Freezing and Thawing

Rain

Physical Weathering(Aka Mechanical Weathering)

• physical weathering changes the size and/ or shape of the rock.

• for example, the rock may be broken into smaller pieces- without changing the rock’s chemical composition.

• the rock pieces have the same composition of the original rock, only smaller.

• mechanical weathering breaks rocks into pieces by:

Freezing and thawing

release of pressure growth of plants

actions of animals

abrasion

• Abrasion is the term used to describe the grinding away of rock by rock particles.

ABRASION• When a stream carries along rock particles, they bump and rub against one another and the streambed.

• There are five major natural agents of abrasion:

1. flowing water

2. Moving ice (glaciers) 3. waves 4. wind 5. gravity

FREEZING AND RETHAWING

• when rocks freeze and then thaw, mechanical weathering is at work.

•Frost action is an important agent of physical weathering in climates that undergo seasonal temperature changes alternately above and below 0 degrees C.

•In weathering by frost action, water seeps into cracks in rocks.

• The volume of water increases as it freezes.

• The more times the volume increases, the bigger the crack the rock gets.

• Overtime of frost and defrost, the rock has huge openings that the allow it to fall apart.

The Process of Frost Action

• Plant roots that grow in the cracks of rocks and animals that burrow beneath the ground are important agents of physical weathering. plant grows, opens crevices in the rock little by little.

• Animals that burrow constantly expose new rock surfaces to weathering.

THE DESTRUCTION BY (dun dun dun)

PLANTS and ANIMALS

…kinda

Chemical Weathering• Deep within Earth’s crust, most minerals remain stable

under the conditions in which they were formed.

• However, when these rocks are uplifted to the surface and exposed to the atmosphere and hydrosphere, they often undergo chemical weathering.

• Chemical Weathering changes the mineral composition of rock, thereby forming new substances. •The rusting of iron is an example of chemical weathering.•Iron rusts in the presence of moisture. •The iron atoms combine with oxygen to form rust (iron oxide).

Fe + Water =

Where does this occur the most?

• Heat also speeds most chemical weathering.

Thus, chemical weathering takes place most rapidly in warm, moist climates.

Erosion•Erosion- is the transportation of sediments.

Erosion (cont)•These sediments will be deposited in a different location.

Agents of Erosion

• the forces of weathering break rocks into smaller and smaller pieces.

• Erosion then carries them away.

• Erosion is the movement of rock particles by four specific agents:

Wind

Water Ice

Gravity

• Weathering and erosion work together continuously to wear down and carry away rocks at Earth’s surface.

How Are Weathered Materials Transported?

•rocks that have been broken into fragments, regardless of the size of the fragments are called sediments.

•The mineral composition or other characteristics of sediments may be unlike the properties of the underlying bedrock.

•In such a case, the sediments must have been formed elsewhere and then transported from their place of origin.

Erosion by Gravity•Mass Movement or Mass Wasting- the downhill movement of rock or sediment without being carried by water, wind, or ice.

Water doesn’t generally carry the sediment, but it loosens it up and allows it to move more freely.

Mass movement includes slow creep, slumping, landslides, and even the falling of individual rocks.

Erosion By Water•running water is the main agent of erosion in moist areas.

Running water transports sediments in several ways:

The smallest particles are carried in solution.

These particles are so small they cannot be filtered out of the water.

Sediments in suspension can be taken out of the water with filters.

However, these particles are too small to settle on their own.

Erosion by Water (cont)•The flowing water rolls or bounces the largest and most dense particles along the streambed.

•Particles in solution and suspension can be carried by slow moving water.

•However, particles rolled along the bottom of the stream require faster stream velocities to move them.

Sediments in Water•A convenient method to estimate the velocity of a stream is to observe the size of the sediment particles that have been carried along the bottom of the stream.

•Faster streams contain larger particles of sediment.

•Slow moving stream can transport only the smaller sedimentary particles.

Velocity of Streams

•This means the speed of the stream.

•The slope (gradient) and the amount of water flowing in the stream (discharge) control the stream’s velocity.

•As the stream gradient increases, so does the velocity of the water flowing in the stream.

•Velocity is also increased by an increase in the amount of water flowing in the stream.

Flooding

•Most of the erosion caused by running water takes place when streams are in flood.

•Flooding causes an increase in both the amount of water and the velocity of the floodwaters.

•Therefore, large boulders can be moved during a flood.

Streams and Erosion•the speed of a stream is a balance between the force of gravity pulling the water downhill and the frictional forces slowing the stream.

•water usually flows fastest near the center of the stream away from the stream banks and the streambed.

•There is even a small amount of friction caused by the air above the water.

•The fastest water is therefore midstream right below the surface of the water.

Streams and Erosion (cont)•- streams with broad, flat valleys often develop S-shaped curves called meanders.

•at a bend in a stream, the fastest flowing water swings to the outside of the bend, causing erosion along the outer bank of the meander.

•The slowest moving water stays to the inside of the bend, causing deposition along the inner bank of the meander.

Erosion By Wind

•wind can pick up loose rock materials, such as sand, silt and clay, and carry them away.

•Wind erosion occurs mainly in areas, such as deserts and beaches, where there is little plant life to hold the soil in place.

Erosion By Ice•if more snow were to accumulate in the winter than melted in the summer, the snow on the bottom would turn to ice.

•When the ice became thick enough, its weight would cause it to move under the pull of gravity.

•Glaciers- are large landmasses of slowly flowing ice.

•As a glacier moves it carries, pushes and drags loose rock material.

•Glaciers with rocks in it acts as a huge abrasion system.

Glaciers and Erosion•Glaciers make a U shaped erosion while streams make a V shaped valley.

Characteristic Changes Caused by Agents of Erosion

•each agent of erosion causes characteristic changes in the particles it erodes.

•Running water leaves sediments are usually rounded and polished

•Wind leaves the rock flat and angular

•These angular rocks that are eroded from sand or ice crystals are called ventifacts.

•Rocks that are usually more polished and scratched due to the dragging of the glacier (ice).

Deposition• Deposition: when the agents of erosion stop transporting sediments.•This process is also called sedimentation.•The agents of erosion are the same as the agents of deposition. • Factors that affect Deposition:1.Particle Size2.Particle Shape3.Particle Density

Particle Size

• Smaller particles settle out…• SSSSLLLLOOOWWWWLLLLYYYY

• Larger particles settle out…• QUICKLY

Particle Shape

• Flat, angular pieces of particle settle out…• SLLLOOOOWWWWLLLLYYY

• Smooth, rounded pieces settle out…• QUICKLY

• Reason: there is less friction on a smooth, round piece because there is less surface area.

Particle Density

• More dense particles settle out more quickly then less dense particles.

Settling Rate v. Settling Time

• Settling Rate: how fast a particle settles over a specific distance. (cm/s)

• Settling Time: the time it takes for a particle to settle. (s)

• There is an inverse relationship to these two.• Ex.) The shorter time it takes for a penny to

go through water, the greater the settling rate.

Sorting of Sediments

• Vertical Sorting:• When sediments are deposited into a still or

….• SHHHHHHHHHHH• Quiet water

• Horizontal Sorting:• When sediments are deposited from a source

of running water.

Vertical Sorting

Particle Size:Largest deosited firstSmaller on top of that

Particle Shape:Round and smooth settle firstFlat and angular settle on top of that

Horizontal Sorting

Particle Size:Largest settle out quicker because velocity decrease at the mouth of a riverSmallest settle out further because a slower velocity can move them more

The Characteristic Deposition by Agents

• Gravity:• Sediments are not sorted• Water:• Depends• Wind:• Windward (gentle gradient) and leeward

(steep gradient)

The Characteristic Deposition by Agents

• Ice:• Unsorted deposits• Glacial Erratics: • Large boulders moved by ice; found in random

places• Striations

How Do Soils Form?

• Soil is the mixture of weathered rock, microorganisms, and organic remains that usually covers bedrock.

• The composition of a soil depends on the rocks from which it weathered and the local climate.

• Physical weathering breaks down solid rock into small particles.

• Chemical weathering changes the minerals, often increasing the clay content.

• The decay of organic remains produces organic acids, which accelerate chemical weathering.

Let’s See, Very Scientifically, How Soil Is Formed

Different Layers of Soil• The gradual formation of soil in place

produces layers known as soil horizons.•The top layer is usually the best layer for growing crops because it is rich in dark-colored organic matter called humus. •However, some important minerals maybe have been transported deeper into the soil by ground-water infiltration.

•The lowest layer of the soil is broken bedrock, which may merge into solid bedrock.

- Most of the soils of New York State do not show the complete development of horizons.

THE LAYERS ILLSUTRATED

Protecting the Soilsoil is a resource that must be protected.

It may take hundreds of years for one cm of topsoil to form.

Human technology has contributed to the loss of soil.

Mining took rocks and soil form the original locations.

By killing plant covers, bad farming and forestry practices, the soil is left exposed and unprotected.

Sherman’s March to the Sea