bellwork 1: 1-8-14

Write briefly about a truly scientific observation you made over the break.

I will only call on 3 of you to share

Bellwork 1: 1-8-14

Chapter 8

Weathering and Soil Formation

Review: What are mountains made of?RocksHow are rocks made into mountains?Plate tectonicsWhat do you think happens to rock once it is

exposed to the surface of the Earth?Weathering and Erosion

Section 1: Rocks and Weathering

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

Heat, cold, water, ice, oxygen, and carbon dioxide are elements of weathering.

Can you think of examples of weathering?

Weathering

Weathering breaks down rock…

Erosion is the removal of rock particles by wind, water, ice and gravity.

Weathering and erosion work together to break down and carry away rocks at Earth’s surface

Erosion

Uniformitarianism is the principle that states that the process we see today are the same as those in the past.

This is how scientists make hypotheses about things that occurred in the past.

Uniformitarianism

Mechanical Weathering is when rock is physically broken into smaller pieces.Smaller pieces are the same composition as the larger pieces

Takes long periods of timeCan break down mountains!

2 kinds of Weathering: Mechanical & Chemical

Freezing, thawing, release of pressure, plant growth, animals, abrasion

Causes of Mechanical Weathering

Abrasion is the grinding away of rock by particles carried in wind, water, ice, or gravity.

Abrasion

Abrasion

Ice wedging is the process of liquid water settling into cracks in rocks, freezing and cracking the rock as it expands

Ice Wedging

Ice Wedging

Chemical weathering is the process that breaks down rock through chemical changes.

Causes include action of water, oxygen, carbon dioxide, living organisms, and acid rain

Chemical Weathering

Chemical weathering can change or produce new minerals as it breaks down rockExample: granite is made of several minerals (feldspar, quartz, & mica)

During chemical weathering, the feldspar minerals are changed to clay minerals.

Chemical Weathering

Chemical weathering creates soft spots or holes in rocks so the rock breaks apart more easily

Chemical and mechanical weathering work together how?Mechanical weathering creates more surface area to be exposed to chemical weathering

Chemical and Mechanical Weathering Work Together

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

Erosion is?the removal of rock particles by wind, water, ice and gravity.

Review

Uniformitarianism is? the principle that states that the process we see today are the same as those in the past.

Mechanical Weathering is? when rock is physically broken into smaller pieces.

What is this an example of?

What is this an example of?

Chemical weathering is? the process that breaks down rock through chemical changes.

Chemical and mechanical weathering work together how?

Mechanical weathering creates more surface area to be exposed to chemical weathering

Read about the 5 types of chemical weathering.

In the same notes we have been working on, tell how each of these elements helps to break down rock.

On your own

Water: dissolves rockOxygen: when in contact with iron it oxidizes (rusts) makes rock crumbly and brown/red.

Carbon dioxide: dissolves in water and creates weak acid (carbonic acid). Easily weathers rocks

Chemical Weathering

Living Organisms: Plant roots can produce weak acids that break down rock

Acid rain: chemicals from burning fossil fuels (sulfur, carbon, nitrogen) combine with water vapor and fall as acid rain. Acid easily breaks down rock.

Chemical Weathering

Slate tombstones from the 1700s are less weathered and easier to read than marble tombstones from the 1800s.

Why?

Slate vs Marble

Factors that affect the rate of weathering are the type of rock and the climate.

1. Type of rock: type of minerals determine how fast a rock weathers

Permeable rocks (those with air holes) allow water to seep in

Rate of Weathering

2. Climate: Average weather in an areaBoth chemical and mechanical weathering occur faster in wet climates.

Chemical reactions occur faster at higher temperatures

Hot, wet climate = faster rate of weathering

Rate of Weathering

Bellwork # ? 1-13-14Write briefly about a scientific observation you made recently.

How Soil Forms

With a partner, or on your own:1: Read over section 22: make a visual glossary for the highlighted and/or bold terms

3: Complete the soil section of our handout from Friday.

4: Answer the assessment questions on page 254

How Soil Forms: Chapter 8, Section 2

Soil: loose weathered material on Earth’s surface in which plants grow

Bedrock: solid layer of rock beneath the soilThe base for the soil above.

Soil Formation

Soil is a mixture of rock particles, minerals, decayed organic material, water, and air.

Humus: The dark-colored substance that forms as plant and animal remains decay.

Humus has nutrientsFertile soil has all of the nutrients plants need to grow.

Soil Composition

S

Sand, silt, and clay are the three types of rock that make up most soil.

Clay=holds too much water, could drown plants

Sand=not enough water/nutrients

Loam=Just the right combination. Crumbly, holds air and waterEqual parts sand, clay, silt

Soil Texture

Soil is constantly being formed.Soil Horizon: a layer of soil that differs in color and texture from the layers above or below.

Topsoil: crumbly, thick, brown mixture of clay, humus, and other minerals.

Subsoil: contains clay and other particles, but little to no humus.

Soil Formation

Look at the map and reading on page 251 and answer the following questions:

1. What affects the type of soil that forms from bedrock in a region?

2. Why might different soils in Arctic regions have similar characteristics?

3. Which soil would be similar to that in prairie region of the U.S.- a soil in the Brazilian rain forest or a soil in the grasslands of Argentina?

4. Which soil type exists where we live? What climate and vegetation types occur in our region?

5. Why does soil type vary across the country?6. In which part of the country are tundra soils

found?

Soil Types

Same as before: pages 252-2531. How does organic matter like litter

become humus?2. Where does most of the organic

matter go?3. Why does Humus remain?4. Why is humus essential for plant

growth?5. How are the organisms in the

illustration adapted to living in soil?6. In which part of the soil would you

expect to find the fewest examples of plant and animal life? Explain.

Living Organisms

Natural resource: anything in the environment that humans use.

Soil is one of the Earth’s most valuable natural resources because everything that lives on land, including humans, depends directly or indirectly on soil.

Soil Conservation

Soil is a limited natural resource because there is limited supply and:

Less than 1/8 of the land on Earth is well suited for farming.

It takes a long time for it to formHundreds of years for a few centimeters to form

Soil conservation

The value of soil is reduced when soil loses its fertility and when topsoil is lost due to erosion.

Soil is exhausted when it loses its fertilityOver farming of the cotton crop depleted and exhausted thousands of acres of farms in the South

George Washington Carver discovered that certain plants (peanuts, beans, and other legumes) replaced these nutrients and farmers returned to the South.

Soil Damage and Loss

Wind and rain can quickly erode exposed soil

Soil with plants on it are stronger against erosion because they break the force of the rain and their roots hold the soil together against the wind and rain

Loss of Topsoil

Late 1800s farmers settled the Great Plains

The region has very fertile soil, but also experiences extensive droughts

Farming (plowing) exposed the soil.

Dust Bowl

During droughts the soil dried, turned to dust, and blew away

1930 a great drought dried the soil and blew millions of tons of topsoil across the U.S. (as far as NYC!)

Farmers began to help conserve soil after this!

Dust Bowl

Soil conservation is the management of soil to prevent its destruction.

Methods:1. Contour plowing: plow fields along the curves of a slope to decrease runoff and erosion

Soil Conservation

2. Conservation plowing: old crops are left to help return nutrients and hold soil in place

3. Crop Rotation: planting different crops in a field every year

Cotton and corn absorb a lot of nutrients.

The following year a low-absorption crop (like oats, barley or rye) is planted

The year after that a plant that restores nutrients, such as legumes, is planted.