STUDY GUIDE CHAPTER 2

The soil loss on the southern Great Plains in the 1930s caused the area to be called what?

the Dust Bowl.

The B horizon consists of?

Subsoil

How would you compare young soil to soil that has been around a long time?

Young soil has less organic matter than old soil.

What are the groups scientists classify soil in?

Climate, plants and soil composition.

Farmers conserve soil by leaving dead stalks and weeds in the ground during?

Conservation Plowing

What is loam?

A crumbly, dark brown soil that has equal parts of sand, silt, and clay. It is the best soil for plant growth.

Classify as mechanical or chemical weathering: (1) cracks in a sidewalk to a tree; (2) limestone with holes like Swiss cheese; (3) a rock that slowly turns reddish brown.

1. Mechanical weathering 2. Chemical weathering? 3. Chemical weathering

What are lichens?

A simple slow-growing plant that typically forms a low crustlike, leaflike, or branching growth on rocks, walls, and trees.

What is the removal of rock particles by gravity, water, wind, or ice?

Abrasion

What is the cause of coal, oil, and gas burning?

Acid rain

What is a natural resource?

Anything in the environment that humans use.

What is the layer below the C horizon?

Bedrock

Which element is especially rich in humus?

Carbon

When what becomes dissolved in rainwater and sinks into the soil, the result is an acid that can weather marble?

Carbon Dioxide

What is the cause of weathered marble and limestone?

Carbonic acid.

How do conservation plowing and crop rotation contribute to soil conservation?

Conservation plowing (low-till or no-till plowing): the farmers disturb the soil and its plant cover as little as possible. It is conserved by the dead weeds and stalks from previous years are left to add nutrients, remain moisture, and hold the soil in place. Crop rotation: farmer's plant different crops every year which absorb different amounts of nutrients. The farmer goes through a cycle each year, first by planting corn which take large amounts of nutrients. The next year he will plant crops with small nutrients like oats or rye. The year after that he will plant alfalfa or beans to restore the nutrients.

How does contour plowing conserve soil?

Contour plowing conserves soil by plowing their fields along the curves of the slope, which helps prevent excess rainwater from runoff and helps prevent the soil from washing away.

The practice of plowing fields along the curves of a slope is called what?

Contour plowing.

What is a primary ingredient of humus?

Decayed organic materials.

The humus in soil is produced by what?

Decomposers

What can rainwater do?

Dissolve minerals that bind together rocks.

What is the role of gases such as carbon dioxide and oxygen in chemical weathering?

Gases in chemical weathering change once they under go the touch of water. For example, when carbon dioxide touches water it dissolves and sinks through air pockets into the soil. Then, it will create a weak acid which is called Carbonic Acid. Oxygen creates oxidation when it is in the presence of water. Oxidation is rust which is a soft, crumbly texture that is a red/brown color.

What did George Washington Carver teach farmers in the South in the early 1930s?

He taught methods of soil conservation.

What type of climate is best for weathering.?

Hot and warm (tropical)

The decayed organic material in soil is called?

Humus

The process that splits rock through freezing and thawing is what?

Ice Wedging

Suppose a rock contains iron. How might the rock change over time?

If the rock contains iron, overtime it will rust because only rocks containing iron can rust. It will rust by being exposed to oxygen while it is wet.

If mechanical weathering breaks a rock into pieces, how would this affect the rate at which the rock weathers chemically?

It affects the rate by breaking rocks into pieces, increasing the rate at which the rock will weather chemically because breaking the rock exposes more surface area to weather.

Why is top soil darker than other levels of soil?

It contains more organic matter.

The layer of plant remains at the surface of the soil is called?

Litter

Soil that is made up of roughly equal parts of sand, clay, and silt are called what?

Loam

What type of soil is best for growing plants?

Loam.

Plant roots that are forced cracks in rocks farther apart are the agent of what?

Mechanical weathering

How can plants act as an agent in both Mechanical and Chemical Weathering?

Mechanical: there is plant growth that occurs which makes the rocks crack due to the roots. Chemical: there is living organisms which slowly dissolve by releasing acids through the roots, lichens.

What are nodules?

Nodules are on the roots of plants, they contain nitrogen which fixes bacteria.

What are decomposers?

Organisms that break down animal and plant remains and waste.

What gas caused the rock containing iron to oxidize?

Oxygen

What are rocks that weather easily due to being filled with tiny air spaces?

Permeable rocks

How do plants cause mechanical weathering?

Plants cause mechanical weathering by cracking rocks with their roots. During the growth of plants, the roots crack the rocks farther and farther apart, causing mechanical weathering.

Acid Rain results in what?

Rapid Chemical Weathering

Name the types of mechanical weathering.

Release of pressure, freezing and thawing, plant growth, animal actions, and abrasion.

What five materials make up soil?

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

What exactly is bedrock?

Rock that has not been weathered.

What is the portion of soil that comes from weathered rocks?

Sand, silt, and clay.

Which plants are usually the first to live in soil?

Simple plants (pioneer species)

Is weathering slow or fast?

Slow

The management of soil to prevent its destruction is referred to as?

Soil conservation.

Briefly describe how soil is formed.

Soil is formed through the process of broken down rock that is weathered and mixed with other minerals on the surface of Earth. It is constantly being formed wherever bedrock is exposed.

How do soil organisms affect the soil?

Soil organisms affect the soil by making humus to make the soil more fertile OR organisms mix the soil to create spaces for air and water.

Compare and contrast the layers in the diagram below in terms of their composition and humus content.

The C horizon is formed first with bedrock weathering and rock breaking up into soil particles. Next, the A horizon is developed as plants add organic material to the soil and plant roots weather pieces of rock (top soil). Next, the B horizon is formed as rainwater washes clay and minerals down from the A horizon.

What is abrasion?

The grinding away of rock by other rock particles carried by wind, water, ice or gravity.

What is soil?

The loose, weathered material on Earth's surface.

Name and describe the middle layer of the soil.

The middle layer of the soil is the B horizon (subsoil). This horizon forms last after rain water washes minerals down from the A horizon.

What is erosion?

The movement of rock particles by wind, water, ice and gravity.

What organism does most of the work in mixing humus into soil?

The organism that does the most work in mixing humus into soil is Earthworms. They eat their way through the soil, they carry humus down to the subsoil up to the surface. Also, the soil they eat is passed out as waste, which is enriched with substances that plants need to grow, such as nitrogen.

What is weathering?

The process which breaks down rocks and other minerals at Earth's surface.

What does the rate of weathering depend on?

The rate of weathering depends on the type of rock and climate.

What did the role of grass play in conserving the soil of the prairies?

The role the grass plays in conserving the soil of the prairies is that the roots extend deep into the ground, helping the grass survive harsh weathers and conditions. The grass also anchors the roots into the ground which doesn't allow the soil to blow away.

What is the principle of Uniformitarianism?

The same processes that operate today operate in the past.

How will the surface area of a rock affect its weathering?

The surface area of a rock will affect its weathering because jagged/ sharp edges will weather first, due to having the most surface area.

What is sod?

The thick mass of roots at the surface of soil in a grassland.

Name the top layer of soil and describe it.

The top layer of soil is the A horizon (top soil). This soil is rich in humus and very fertile. Also, this layer forms after the C horizon. The A horizon is made of decayed organic material.

What would happen if lichens did not occur?

There would be almost no organic material in lower levels of soil.

What are fungi, bacteria and earthworms?

These are decomposers.

What do weathering and erosion have in common?

They both break down rocks and minerals.

What affect do plant roots have on rocks?

They break rocks apart.

Legumes

They have small lumps on their roots that contain nitrogen-fixing-bacteria, which make up an important nutrient that is used by plants (peanut plant).

Which contains more humus, top soil or sub soil? Which has higher fertility? Explain.

Top soil contains more humus because it is made up of lots of it on top of clay and other minerals. Meanwhile, subsoil has very little humus, although contains lots of clay and other minerals. Top soil is more fertile because lots of humus, clay and other minerals support plant growth. On the other hand, subsoil has very little humus to support plant support.

What is the most important agent of chemical weathering?

Water

Name the types of chemical weathering.

Water, oxygen, acid rain, living organisms, and carbon dioxide.

What can soil be lost during?

Weathering and erosion.