January 18, 2013 Q-2 Pg.Daily Goal: We will be able to articulate the difference between erosion and deposition. We will demonstrate how geographical features influence deposition.

Homework: Study for Thursday and Friday’s mastery quiz! Enjoy your long weekend!

Science Starter: 1.What is deposition?2.What factors might determine why sediment builds up in one area and not in another?3.What is the difference between weathering, erosion, and deposition?

Review Questions…We’ve been talking about weathering, erosion and the impact of human

actions.

Identify as mechanical or chemical weathering:n Acid rain slowly wears down a statue.

1. A rock rolls down a hill and cracks in half.

2. A tree root grows into a rock, breaking it into small pieces.

3. Oxygen in the atmosphere reacts with iron in rocks creating a rusty color.

Major types of erosion

1. Stream bank

2. Topsoil

3. Coastal

What words do we need to know to be able to speak like scholars about this subject?

***Write this in your glossary***Erosion – the process in which sediment is picked up and moved from one place to anotherDeposition – when sediment that is being transported gets dropped in a location

I. Stream bank erosion is the movement of sediment from the sides of streams or rivers. Stream bank erosion is caused by running

water and burrowing animals (like nutria).

What are ways we could stop stream bank erosion?

Does it seem like a natural type of erosion?

So, humans don’t do ALL the damage.

Methods to control stream bank erosion:

The roots of the plants hold soil back!

Manmade nets and mats also hold back

and keep it from washing away!

1. Planting plants on the edge of a stream or river.

2. Placing concrete mats, netting or logs on the sides of a stream.

III. Coastal Erosion is the movement of soil and sediment from coastal areas.

Land + Ocean meeting = the coast

What causes coastal erosion--humans or nature??

All the grass is gone!!

BOTH!

Erosion caused

by Nature

1. Subsidence: when land sinks as sediments compact

2. Hurricanes and storms

3. Sea level rise

Erosion caused

by Humans

1. Building levees

2. Oil field canals

3. Oil & gas production: causes increased subsidence

II. Topsoil Erosion is the wearing away of the top layer of soil due to water runoff or rainfall, wind and gravity.

What exactly is topsoil??

Topsoil is the upper, outermost layer of soil. Usually 2-8 inches deep. It contains most of soil’s living matter and

nutrients. This is where plant roots grow!

Methods to prevent topsoil erosion:

1. No-till farming: soil is not tilled (stirred) and dead plant material builds up and covers the surface of the land

2. Contour plowing: farmers plow in curved rows, parallel to the curve of the land

3. Terracing: farmers cut steps into steep hillsides

4. Cover-crops & Crop Rotation: certain crops are good for restoring the natural balance of nutrients in the soil and preventing erosion

Human impact: It might seem like fun, but when you’re done, you’ve destroyed the earth a little bit…

4-wheeler tracks

Climbing and ‘surfing’ on sand dunes in Namibia.

WHAT DO YOU THINK?

Why is it important to prevent erosion of topsoil?

Why do farmers work so hard to make sure their soil is good?

We know the earth has been here for a long time… and things happen slowly.

It takes approximately 100 years for one inch of topsoil to be created through the weathering and erosion of rocks.

There are 25 billion tons of topsoil lost each year due to erosion!

We need topsoil to grow crops so we have food to eat.

Let’s try it out!

You will need: 1 clear box filled ¼ of the way full with sand 1 straw 2 rocks

What is soil?

What is it made of?

What’s in it?

Soil is a mixture of pieces of rock, organic matter, air and water.

Rock fragments (pieces) can be:

SandSiltClay

Humus isthe organic part of soil; decaying plant and animal matter, such as leaves, roots and dead animals.

Soil is made in layers, which are called horizons.

The layers of soil are made of different types of sediment and nutrients.

There are 3 horizons (A, B, C) that form a soil profile.

SOIL HORIZON

LAYER ORGANIC MATTER

COLOR NUTRIENTS

A Horizon

Topsoil High Darkest High

B Horizon

Subsoil Low Lighter Low

C Horizon

Weathered Bedrock

Low Lightest Low

**Fill in the whole chart!**

The layers!

A Horizon

B Horizon

C Horizon

Bed rock

WHAT IS THAT???

In Louisiana there is NO C Horizon. So, there is NO bedrock layer under the soil.

What is a possible effect?

Meaning, what happens because there is not bedrock under the soil in Louisiana?

Exit Slip

1. Which layer of soil is most important for growing crops?

2. Which layer of soil contains humus?3. Which layer of soil is made up of

partially broken bedrock?4. What is humus?

a. Parent rock c. Bedrockb. Plants and animals d. Horizon B

A Horizon

B Horizon

C Horizon