January 16, 2013 Q-2 Pg.Daily Goal: We will be able to identify and explain 3 processes that shape the earth through weatheringHomework: Turn in missing work! Finish weathering packet

Science Starter: 1. What type of rock is

the Grand Canyon?

2. What do you think may have created the shape of the canyon?

Rocks, Weathering, and Soil Information

In this PowerPoint, anytime that you see words written in purple, it means that you nee

to write it down.

Weathering and Erosion***Write this in your glossary***

• Weathering: the breaking down of rocks into smaller pieces

• Erosion: the transport of sediment • Both of these processes take a very

long time to occur

The Effects of Weathering• All exposed rock is in the

path of weathering and erosion.

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

• Heat, cold, water, ice, carbon dioxide, oxygen etc.. all contribute to weathering.

Weathering and Erosion• Weathering examples:

– Repeated freezing and thawing. – Rainwater dissolving minerals.

• Weathering and erosion work together to carry away the rocks at the surface.

• There are two types of weathering:– Mechanical Weathering– Chemical Weathering

Mechanical Weathering• Mechanical Weathering: when rock is

physically broken into smaller pieces that have the same chemical composition as the rock they came from; changing a

rock’s appearance– Examples:

• freezing and thawing,• release of pressure,• growth of plants, • actions of animals, and • abrasion (grinding away of rock by particles in the wind and water).

Weathering– Frost wedging: water freezes in cracks of the rocks

and cracks the rock apart – Wind and water: break pieces of rock apart – Roots can break rocks apart too

Brain Boost!• Frost wedging occurs when water

collects in cracks or openings in rock, then freezes and expands. This expansion of the water can force the rock to split. This is an example of what kind of weathering?A. ThermalB. ChemicalC. BiologicalD. Mechanical

Weathering • Chemical Weathering: chemically

changing the rocks to break them down

Chemical Weathering• Chemical Weathering: the process that

breaks down rock through chemical changes and produces rock particles that have a different mineral makeup from the rock they came from. – Examples:

• Hot or soft spots in rock • Water• Oxygen• Carbon Dioxide• Living organisms• Acid Rain

Water• Water weathers rock by dissolving

the minerals in it.

Oxygen• Iron combines with

oxygen in the presence of water in a processes called oxidation

• The product of oxidation is rust.

This rock in Utah is red because of the oxidation of iron in the sediment when the

rock was being formed.

Carbon Dioxide• CO2 dissolves in rain water and

creates carbonic acid.• Carbonic acid easily weathers

limestone and marble.

Living Organisms• The roots of Lichens that grow on rocks

produce weak acids that chemically weather rock

Acid Rain• Compounds from burning fossil fuels (coal,

oil and gas) react chemically with rain water and forms acids.

• Acid rain causes very rapid chemical weathering.

1908 to 1969

Acid rain has eaten away this limestone statue.

Rate of Weathering• The most important factors that determine the rate

at which weathering occurs are the type of rock and climate .

• Type of Rock– Minerals will determine the rate.– Permeable rocks (full of tiny air spaces) weather faster.

• Climate:– Weathering occurs faster in wet climates and higher

temperatures.

Brain Break:• Take one minute to answer

this question:– Think about when we dissolved a

piece of chalk in vinegar. Was that an example of physical or chemical weathering? List at least 2 reasons that support your answer.

I will stamp completed work.

Let’s do some more weathering!

EXIT TICKETLet’s revisit our answers. Answer these questions again using what you learned.

1. What type of rock is the Grand Canyon?

2. What do you think may have created the shape and color of the canyon?

Soil Formation• Over many years, weathering

and erosion will cause the formation of soil.

• Soil is the loose, weathered material on the Earth’s surface in which plants can grow.

• Soil forms as rock is broken down by weathering and mixes with other materials on the surface.

Soil Composition• Soil is constantly being

formed wherever bedrock is exposed.– Bedrock is the solid layer of

rock beneath the soil. • Soil is a mixture of rock

particles, minerals, decayed organic material, air, and water.

Soil Composition and Texture• The decayed organic

material in the soil is humus. – Humus is a dark-colored

substance that forms as plant and animal remains decay.

• Soil texture depends on the size of individual soil particles.– Soil texture is important for

plant growth.

Soil Horizons• A soil horizon is a layer of soil

that differs in color and texture from the layers above or below it.– Topsoil (A horizon) is a

crumbly, dark brown soil that is a mixture of humus, clay, and other materials.

– Subsoil (B horizon) usually consists of clay, and other particles washed down from the topsoil, but little humus.

– C horizon contains only partly weathered rock.

Life in Soil

• Some organisms mix the soil and make spaces in it for air and water.

• Other soil organisms make humus, the material that makes soil fertile.– Humus forms through decomposition.– Fertile soil is rich in nutrients that plants

need.• As plants shed leaves, they form a

loose layer called litter.

With and Without Worms

Soil Types in the U.S.• Tundra Soils• Northern Forest

Soils• Prairie Soils• Mountain Soils• Southern Forest

Soils• Desert Soils• Tropical Soils

Soil Conservation• Soil is one of Earth’s most

valuable resources because everything that lives on the land depends directly on indirectly on soil.

• Fertile soil is valuable because there is a limited supply. – Less than 1/8th of the land on

Earth has soils well suited for farming.

Soil Damage and Loss• Soil can become

exhausted, or lose its fertility.

• Soil can also become lost to erosion by water and wind. – Water erosion can occur

wherever soil is not protected by plant cover.

– Wind erosion caused the Great Dust Bowl!!

The Dust Bowl• In the 1930s plowing removed the grass form

the Great Plains and exposed the soil. In times of drought, the topsoil quickly dried out, turned to dust, and blew away.

• This event helped people appreciate the value of soil.

• Check It Out!!

Soil Lost To The Seas!!

Soil Conservation• Soil Conservation is the

management of soil to prevent its destruction.

• Two ways that soil can be conserved include contour plowing and conservation plowing.

Contour Plowing• Contour plowing is the

practice of plowing fields along the contours of a slope.

• This helps slow the runoff of excess rainfall and prevents it from washing the soil away.

Conservation Plowing

• Conservation Plowing disturbs the soil and its plant cover as little as possible.

• Dead weeds and stalks of the previous year’s crop are left in the ground to help return soil nutrients.

Erosion• Erosion reshapes

earth’s surface by moving sediment

• What moves the sediment?– Water– Wind

• Erosion is highest in areas with no vegetation

How do we prevent erosion?• Create a windbreak by planting a row of trees • Strip farming: alternating crop types to help hold the

soil in place• Contour farming: farmers plow at right angles to the

slope of a hill. This keeps the soil from washing away

Sample Question…

A farmer is concerned about the erosion of his soil by the action of the wind. Which would be the best way for the farmer to reduce wind erosion?A. Add worms to the soil so that the drainage improvesB. Fertilize the soil so that plants have more nutrients C. Plant a row of trees that act as a wind break D. Water the soil less often so that the soil dries out