• The breaking down of rocks into smaller pieces.

• Weathering is the breaking up of rocks. It is caused by water, ice, chemicals, plants and changing temperature. There are two types of weathering:
• physical or mechanical weathering
• chemical weathering

• Physical or mechanical weathering breaks rocks into pieces.
Temperature change is the major force in this type of weathering. Water fills the cracks of rocks naturally during rainstorms but if the temperature falls and causes the water to freeze it expands in the cracks and may push hard enough to split the rock.
• In a similar way, plants, especially trees, may grow in the cracks of rocks sending there roots down deep into the cracks looking for water. As the roots grow the pressure can cause the rock to split.
• Other types of Physical weathering:
– Rushing water wearing away stones such as in a stream
– Wind carrying bits of sand

• The process that breaks down rock through
chemical changes.
• Chemical Weathering is caused by action of water. This type of weathering affects the minerals within the rocks. Rain, streams, and ocean water dissolves minerals from rocks, causing the rocks to crumble.

• Iron combines with oxygen in the presence of water in a processes called oxidation
• The product of oxidation is rust

• CO acid
2 dissolves in rain water and creates carbonic
• Carbonic acid easily weathers limestone and marble

• Compounds from burning coal, oil and gas react chemically with water forming acids.
• Acid rain causes very rapid chemical weathering

• Created by chemical weathering of limestone

• Perform weathering lab stations. In the weathering stations the following activities are used. One station for each activity. Lab sheets for each station are attached at the end of the lesson.
• Station 1. Compare and record the reaction of antacid tablets in water (50ml). The comparison is a whole tablet vs. crushed tablet.
• Station 2. Test the effects of vinegar (acid rain) on copper
(pennies). 25mL and 1 penny. You should record observations initially and then again after 5 minutes.
• Station 3. Compare and record the reactions of chalk (limestone) in vinegar (25 mL).
• Station 4. Test and record the effects of sugar cubes and gravel shaken together in a jar.
• Discuss the effects of each process.

• The main product of weathering is soil . Soil is a mixture of weathered rock, minerals, and other things. It also has bits of decayed plants and animals, which is called humus.
Humus is a dark color and adds lots of nutrients to the soil.
Plants then use these nutrients to help them grow. Humus is very rich and it also soaks up water to help keep the soil moist. Water, air, and living things are also found in soil.

What kinds of living things can be found in soil?
• Plant roots: Take in water and nutrients; help hold the plant in place. They also help hold the soil in place to prevent EROSION.
• Ants, earthworms, moles, and other living things that burrow or dig through the soil.
Their burrows help air and water get into the soil. They also leave their waste in the soil which adds nutrients.

• It begins with weathering. Weathering breaks down rocks into smaller and smaller pieces. These tiny bits of weathered rocks build up in layers. Living things die and decay in the weathered materials and become humus. Over time, layers of soil form.
It takes a long time for soil to form, up to 1,000 years for just one centimeter.
• Because soil is formed from the weathering of rocks, it is considered a renewable natural resource. Renewable, because it is always being “renewed” through the weathering of rocks.
• For this reason, it is important to prevent soil erosion. We will discuss different things that cause erosion, and ways to prevent it, in the next lesson!

• Topsoil: The top layer. It is usually dark and has the most humus and minerals. You will find most living things in the top layer.
• Below the topsoil is subsoil. It contains less humus.
• Below the subsoil you will find bedrock, or solid rock.

• People describe soil types in all kinds of ways such as heavy, light, sandy, clay, loam, poor or good. Soil scientists describe soil types by how much sand, silt and clay are present. This is called texture . It is possible to change the texture by adding different things. Changing texture can help in providing the right conditions needed for plant growth

• Different soils are found in different places.
Some soil is good for growing plants, while other soil is not.
• Soils differ in color and texture. A soil’s color has to do with what’s in it. For example, red soil may contain a lot of iron. Dark brown or black soil contains a lot of humus.

• In the desert, you might find a lot of sandy soil.
• In a forest, with lots of living things in it, you might find soil with a lot of humus in it.

• Soil texture describes how big the particles, or pieces, of soil are.
• Most soils are either sand, clay, silt, or loam
.

• Sand is the largest particle in the soil. When you rub it, it feels rough. This is because it has sharp edges. Sand doesn't hold many nutrients.
• Loose and easy to dig in.
• Sand particles are so large that water flows through it very easily. Because it doesn’t retain water very well, plants have trouble growing in this type of soil…unless they have special adaptations for growing in dry places, such as long roots.

• Clay is the smallest of particles. Clay is smooth when dry and sticky when wet.
• Soils high in clay content are called heavy soils. Clay also can hold a lot of nutrients, but doesn't let air and water through it well. Because the particles are so closely packed together, roots cannot push through it very well
• Water doesn’t drain through it very easily…resulting in TOO MUCH WATER for the plant.

• Silt is a soil particle whose size is between sand and clay. Smaller than sand, larger than clay.
• Silt feels smooth and powdery. When wet it feels smooth but not sticky.

• This soil is a mixture of sand, silt, clay and humus.
• It is considered to be the perfect soil.
• Holds water well and has many nutrients.
• Lighter and looser than clay.
• Most plants grow well in loam.
• Feels gritty.

• Here is how the particle size would layer:

• Particle size has a lot to do with how well a soil drains water and holds nutrients. To better understand how big these three soil particles are, think of them like this. If a particle of sand were the size of a basketball, then silt would be the size of a baseball, and clay would be the size of a golf ball. Line them all up, and you can see how these particles compare in size.

Look at these:

• Soil is a natural resource. A natural resource is a material on Earth that is necessary or useful for people. It is not man made.
• Because it is made from the weathering of rocks, it is considered a
“renewable” resource. It is renewed, or made again, through a cycle. Though this takes a long time, a thousand years for just 1 centimeter of soil!
• Without soil, plants could not grow, which means people and animals would have no food!

• Most living things need three basic things to survive: food, water, and air. Plants get their nutrients and water from the soil. Although all green plants make their food by photosynthesis , they also need to get nutrients from the soil. These dissolve in water and are taken up by the roots of the plant.

• A plant’s roots hold the plant in the soil, and absorb water and nutrients. They also help prevent the next thing we are going to take a look at: Soil Erosion.