Erosion and Weathering

Effects of Erosion

• Title page “Effects of Erosion”• For each before and after

picture, write your observations of what has changed and your hypothesis (what caused it to change).

Solve the Mystery of the Great Sphinx of Giza:

• Observation: What is different about the Ancient Egyptian Sphinx in the two images?

• Hypothesis: What do you think caused this difference?

Before: After:

Great SphinxObservations:Hypothesis:

Sphinx Mystery Uncovered:• The head was made up of a harder strata—so it avoided a lot of

weathering. (its nose was taken off by soldiers in the 18th century.

• The body was made out of softer limestone (what kind or rock is this?

• Some weathering by wind and sand and dust has occurred.• However, it is believed that flooding from the Nile River led to extreme water erosion.

After:

Solve the Mystery of The Grand Canyon:

• Observation: What is different about the Grand Canyon in the two images?

• Hypothesis: What do you think caused this difference?

Before:

After:

Grand CanyonObservations:Hypothesis:

Grand Canyon Mystery Uncovered:

• Carved out (eroded) by the Colorado River over the past 17 million years.

After:

Solve the mystery of the Statue of Liberty

• Observation: What is different about the Statue of Liberty in the two images?

• Hypothesis: What do you think caused this difference?

Before:

After:

Statue of LibertyObservations:Hypothesis:

Statue of Liberty Mystery Uncovered:

• The statue of liberty is made of copper (like a penny) over time it is being oxidized by water and air– a form of chemical weathering—making it green instead of silver.

Solve the mystery of the landscape:

• Observation: What is different about the landscape in the two images?

• Hypothesis: What do you think caused this difference?

Before:

After:

LandscapeObservations:Hypothesis:

Landscape Mystery Uncovered:

• Glaciers carve through plateaus, mountains and land easily, causing weathering and erosion

•

SandcastleObservation:Hypothesis:

1970s:

1990s:

Today:

Castle Mystery Uncovered:• The largest “active”/ “living”

Sand Dune on the East Coast—Jockey’s Ridge North Carolina

• The amount of sand making up the 420 acres of Jockey's Ridge is equal to about 6,000,000 dump truck loads!

• The Sand is mostly quartz rock which came from the mountains millions of years ago.—what kind of rock is quartz rock?

Castle Mystery Uncovered:

• Each year winds from each directions erode the Dune, picking up sand and moving.

• Over time the Dune moved so much it covered an old Put-put coarse—which the castle was part of.

• Over more time the Dune moved so much that it is uncovering the Put-put coarse and unveiling a weathered/eroded castle—wind and sand weathering.

1. Erosion is the natural moving of material from one place to another.

2. Mountain rivers can form V-shaped rivers and canyons.

Erosion

3. It takes a river millions of years to create a valley or canyon.

• We can see from the examples, dirt and soil can be eroded and change landscapes. What typically needs to happen to the rock before it is eroded?– It needs to be weathered!

Mechanical Weathering Mechanical— when a rock is broken into smaller pieces —doesn’t change the chemical composition of the rockExamples:-- Grand Canyon, carved out by the Colorado River—no change of the rock just denting the rock or changing its shape-- Sphinx of Giza—sand and water both chipped away at the Sphinx changing its shape but not what it was made of.

Think of sand paper or breaking/cracking something!

Types of Mechanical Weathering

• Abrasion: When rocks move (erode), they collide with each other and break apart

• Expansion and Contraction: Heating and cooling causes rock to swell and shrink and crack

• Frost action: Water fills cracks, and then expands when it freezes

• Plants and animals: Plants wedge in rocks, animals tunnel and dig

Chemical--when a rock is broken down through a chemical change Examples:--Statue of Liberty, tarnished/ rusted by the air and water exposure and turned green--Rusting of a bicycle-- Acid Rain can erode statues, gravestones etc.

Chemical Weathering

Think of changing the entire rock!

Types of Chemical Weathering

• Hydrolysis: Hydrogen in water reacts with minerals, creating new compound

• Carbonation: Acid in water causes the rock to dissolve

• Oxidation: The chemical reaction of oxygen with other substances (rust)

Soil

http://www.brainpop.com/science/earthsystem/soil/

How is soil created?

How is soil created?1. Exposed rock

(“bedrock”) starts to be weathered.

2. Wind, moving water, changes in temperature continue the weathering and erosion process.

3. Broken pieces get broken down further and further

How is soil created?

3. Animals & plants aerate the soil and decompose organic matter.

4. Bacteria and fungi grow and produce acids that further break down rock—producing minerals and nutrients for plants.

SoilLoose surface of the earth—made up of rock, decayed plants and animals, air, minerals, water

– Soil types change due to different size mineral particles such as sand, silt and clay

What does soil look like?

Soil Horizons• A Horizon—topsoil• B Horizon—subsoil• C Horizon—

weathered bedrock• D Horizon—

unweathered bedrock

A-horizon =

B-horizon =====

C-horizon ==

D-horizon =

Digging up the Horizons

A Horizon- Topsoil• Nutrient Rich• Usually dark to light

brown• Made up of fine

particles of weathered rock & humus

Humus

•Dark organic (living) material made of dead, decaying plant and animal matter

B Horizon Subsoil• Often red or

brown• Clay, iron oxides

and dissolved minerals washed down from A-Horizon

• Deep roots found in this layer

C Horizon

• Partially weathered rock material (rock fragments)

D Horizon

•Bedrock•Un-weathered

rock material

Exit Ticket:

A

B

C D

?

1.What is soil and how does it form?2.What are the 4 horizons (layers) of the soil and what are they made of?

12.12 Warm-Up1.  Organic matter in soil is made from —

A. Weathered parent rock

B. Decayed plants and animals

C. Acid Rain

D. Carbon Dioxide

2. The formation of a soil is influenced by all BUT one of the factors listed. That factor isA) climate.B) parent rock.C) the partial melting of local granite.D) biologic activity of plants and animals.

3. What is the process by which organic matter breaks down to become part of the soil?A) compactionB) decompositionC) erosionD) weathering

Let’s Hear A Little About Human Impact –

Video!

Human Impact on Soil and Erosion

• Human Activity is the main force of speedy (accelerated) erosion.

• Land-Use Practices that remove plants from an area increase erosion because the plant roots hold down the soil and prevent it from being washed or blown away1. Farming (plowing and over-

grazing)2. Construction and Development3. Mining

Farming

• Over-grazed (by animals) or over-plowed (by humans) soil will be less fertile and will most likely be carried away by water and wind

• Plants help in reducing soil erosion by holding the soil in place

Construction and Development

• People dig away soil to make roads, houses, or other buildings

• The soil can be washed or blown away because it’s plant cover has been removed (no roots to hold it down).

• Sediment often goes into rivers, streams or lakes – This can harm organisms, flood rivers, and fill

up lakes

Mining

• Digging of mines involves the removal of plants and soil from the surface of the ground

• Rocks and minerals are then exposed to the air and rainwater, which speeds up chemical weathering

Solutions

• Conservation Tillage: Reducing the number of times fields are plowed

• Crop rotation: Planting different crops in different years makes soil more fertile

• Fences/Windbreaks: Fences or rows of trees around fields can prevent soil from being eroded by wind

• Terraces: Flat, step-like areas built on hills to stop the soil from eroding down the hill

Scavenger Hunt