3-1 Rocks and Weathering
The process that splits rock through freezing and thawing is called
Frost Wedging
Soil that is made up of roughly equal parts of clay, sand, and silt is called
Loam
What role do grasses play in conserving the soil of the prairies?
Fertile soil is an important natural resource because
everything that lives on land depends on soil
Acid rain causes rocks to ______
Acid rain causes rocks to dissolve
The decayed organic material in soil is called
humus
Which technique returns nutrients to the soil?
Crop rotation returns nutrients to the soil
In which climate would a limestone monument weather MOST quickly?
a hot and wet climate
If mechanical weathering breaks a rock into pieces how would this affect the rate at which the rock weathers chemically?
The rate of chemical weathering increases as we break the rocks into smaller pieces. This is because there is more surface area as we break rocks into smaller pieces. (Think about if you crush ice into smaller pieces, they will melt faster)
What is the most important role that burrowing animals (like moles or worms) play in the formation of soil?
Why is soil important to people and to other living things?
Plants need soil to grow, and people and other animals eat plants in order to gain energy.
A farmer wants to reduce the amount of runoff in his fields. What is he trying to avoid?
Topsoil erosion
Classify each of the following as mechanical or chemical weathering:
1) Cracks in a sidewalk next to a tree.
2) Limestone with holes like Swiss cheese
3) A rock that slowly turns reddish brown
1) Cracks in a sidewalk next to a tree. - Mechanical Weathering
2) Limestone with holes like Swiss cheese - Chemical Weathering
3) A rock that slowly turns reddish brown - Chemical Weathering
What are two roles living thing play in soil formation? Explain
Making humus and mixing the soil
How did human activities contribute to the Dust Bowl?
People had plowed up the soil, exposing it to erosion. They had also planted crops init that removed nutrients from the soil, making it less fertile.
Mechanical weathering: 1. Animal Actions, 2. Frost Wedging, 3. Plant Growth, 4. Release of Pressure, 5. Abrasion
Chemical Weathering: 1. Water, 2. Oxidation/oxygen, 3. Carbon dioxide, 4. Living organisms, 5. Acid Rain.
What are TWO of the factors that affect how fast mechanical and chemical weathering happen? Explain how each one affects the speed of weathering
The three factors that affect the speed of of weathering are the type of rock, permeability, and climate.
1. Type of rock - the minerals that make up a rock determine how fast it weathers. Rocks made of minerals that do not dissolve easily will weather slowly. Rocks weather faster if they are made of minerals that do dissolve easily
2. Permeability - rocks that are full of tiny holes are permeable. The more tiny holes the rock has the more surface area it has, and so the faster it weathers.
3. Climate - chemical reactions occur faster are higher temperatures, so chemical weathering occurs more quickly where the climate is both hot and wet.
You have one pot of soil that is 1/3 clay, 1/3 sand, and 1/3 silt. You have a second pot that is mostly sand with little silt and clay. Describe what the soil in each pot would look like, and predict which soil would be better for growing plants and why.
The first pot would probably be dark brown, while the soil in the second would be very light and sandy. Loam is a mix of all three and is very fertile so the first would be better for plants.
Explain how conservation plowing and contour plowing help conserve soil.
Contour plowing - farmers plow their fields along the curves of a slope instead of in straight rows, which helps slow the runoff of excess rainfall and prevents it from washing away the soil.
Conservation Plowing - dead weeds and stalks from the previous year's crops are plowed into the ground to help return soil nutrients, retain moisture, and hold soil in place.
Describe the three horizons (layers) of soil.
B Horizon - Often called the subsoil, it usually consists of clay and other rock particles, but little humus. It forms as rainwater washes these materials down from the A horizon
C Horizon - Forms as bedrock begins to weather, which breaks it up into small particles