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EARTH SYSTEMS

here today, gone tomorrowthe effects of erosion

ACHRI/DGS/KFK/081011/V1 DRAFT COPY • ©2011 Delta Garden Study.

Frameworks

sCIeNCeNS. 1.6.1 Verify accuracy of observations. NS. 1.7.1 Interpret evidence based on observations. NS. 1.7.5 Communicate results and conclusions from scientific inquiry.ESS. 8.7.10 Describe ways human beings protect themselves, others and their property from adverse weather conditions. ESS. 8.8.8 Demonstrate an understanding of the agents of erosion: gravity, water, animals, ice, etc.

LaNGUaGe arTsW.5.6.10 Write across the curriculum.W.5.7.10 Write across the curriculum.W.5.8.10 Write across the curriculum.

s objeCTIvesThe students will learn:

objeCTIve #1 To define erosion.

objeCTIve #2 To explain how weathering, erosion and deposition work together to change the land surface.

objeCTIve #3 To describe the main agents of erosion.

objeCTIve #4 To describe how soil erosion can damage agriculture, land management and real estate.

objeCTIve #5 To identify methods to prevent soil erosion.

objeCTIve #6 To appropriately use verbal speaking skills in class discussion with the teacher and Garden Program Specialist.


EARTH SYSTEMS • Here Today, Gone Tomorrow: Teachers’ Guide

Eros

ion

caus

ed by w

ater, wind or agricultural practices can destroy crops. overvIew

Erosion—whether from wind, water, ice or human activities—works in conjunction with weathering and deposition to change the land surface. Several techniques can prevent soil erosion, which is of particular concern to land managers.

GardeN aCTIvITIess Optional: Digging up turf to convert to garden bed

s Conducting erosion experiments

s Plant, harvest and work in the garden following the Garden Guide

s Recipes and Taste tests as time permits (refer to Delta Garden Study Recipe Book)



TIps For TeaChersPre-lesson preparation:

1. Review the “Study Guide for Students” to familiarize yourself with the extent of knowledge this lesson is designed to convey to students. The pages are not designed to be read to class, but rather to function as reference material. During the lesson, teach this material through a combination of lecture, discussion and a question-and-answer session. Time permitting, you and the class might wish to work through this material as a review after you return to the classroom.

2. Review the “Supporting Information for Teachers” for information about erosion experiments.

3. Check for examples of erosion in the garden and on school grounds. Have garden and school maintenance managers have taken steps to control erosion if applicable?

LessoN oUTLINe

activities estimated duration actual duration

in the classroom

s Offer the icebreaker

s Explain erosion

5 minutes

10 minutes

in the garden s Check the school and garden grounds for examples of erosion

10 minutes

s Dig up pieces of sod and samples of bare soil

10 minutes

s Conduct erosion experimentss Pick and taste produce as available 5 minutes

back in the classroom

s Hand out Student Learning Workbooks, review and assign “Take it Home Activity” as homework

5 minutes

gardenmaterials needed

s Fine sand, soil

s Watering can

s Small blocks of ice

s Shallow pan

s Clay, gravel

s Large bucket

s As available, fresh produce from garden

classroommaterials needed

s Student Learning Workbooks



LessoN pLaN

I. Start in the classrooma. Icebreaker

Ask students: “Can you think of an example of erosion on a very large scale?” If they don’t come up with the answer you can give them a hint: “It’s in Arizona....”

Answer: The Grand Canyon is an example of erosion.

II. Take class to the gardens Describe and define erosion. meeTs objeCTIve #1s Explain how erosion works in conjunction with weathering and

deposition. meeTs objeCTIve #2

s Examine the school and garden grounds for examples of erosion, e.g., eroded topsoil on a slope or under a tree, deposition of sand over walkways, parking lots, etc. Explain the major agents of erosion (water, wind, ice, human activities) and link each erosion example to the agent that caused it.

meeTs objeCTIves #1–3

s Following the instructions on page, conduct experiments to study erosion.

meeTs objeCTIves #1–5

s Discuss soil erosion and its impacton land development, especially construction and agriculture.

meeTs objeCTIve #4

s Explain methods to prevent soil erosion and point to examples in the garden, if applicable.

meeTs objeCTIve #5

s Time permitting, instruct students to perform necessary garden tasks.

meeTs objeCTIve #6

s Pick and taste available vegetables. Review how erosion can remove fertile topsoil, which is the soil layer all garden crops require for growth and fruit development, which ultimately represents food for animals and people.

meeTs objeCTIve #4

III. Take class back to classrooms Hand out the Student Learning Workbook as reference material

and class assignment. Review take it home activities and encourage students to do them.

meeTs objeCTIve #6



sUpporTING INFormaTIoN For TeaChers

baCkGroUNd

Erosion is a naturally occurring process that entails the movement of rock and soil particles from one place to another. The loss of soils, particularly fertile topsoil, is an important issue for land managers, as well as home gardeners.

The following experiments will allow students to study the effects of wind, water and ice/glacier erosion and to compare the effect of erosion on bare vs. vegetated soil.

materials neededs fine sands soils watering cans small blocks

of ice

s shallow pans clays gravels large bucket

procedure

wINd erosIoN

Place a cupful of sand into pan and blow on it. Observe what happens.

Discuss: s What size particles would be moved faster

when blown by wind: larger or smaller sized particles?

s Where does this process happen in the garden, on the school grounds, in the community? (Examine garden and school grounds as practical.) United States? Earth?

waTer erosIoN

Place several cupfuls of soil into pan. Tilt the pan and slowly pour some water near the top edge. Let the water run over the soil and then drain into the bucket. Observe what happens.

Discuss: s What happened to the soil where the

water ran over?s Did any soil end up in the bucket? How

did it get there?s Is this process similar to what a river

does?

ICe/GLaCIer erosIoN

Flatten out a piece of clay and put some gravel on top of the clay. Take a small block of ice and rub it back and forth across the gravel that is on top of the clay.

Discuss: s What happened to the surface of the clay?sCould a glacier do the same thing to the

surface of the soil on a larger scale?



soUrCes

The ABCs of Ecology, An Educator’s Guide to Learning OutsidePublication by Ecology Education, Inc., 2006

United states department of agriculture, Natural resources Conservation servicehttp://soils.usda.gov/education/resources/lessons/profile/

Master Gardener Arkansas HandbookUniversity of Arkansas, Division of Agriculture, Cooperative Extension Service, 2000

botanic Gardens Conservation International, Canada, (bGCI) Investing in Nature, a partnership for plants in Canadahttp://www.bgci.org/files/Canada/english_docs/rbg_soilph.pdf

Georgia agriculture education, Georgia middle school agricultural Curriculum, Unit 8, Lesson 4http://aged.ces.uga.edu/

Project Learning Tree. Environmental Education Activity Guide. PreK-81998, 6th edition, American Forest Foundation.

oregon state University, National science Foundation Gk-12, Fellowship programhttp://oregonstate.edu/precollege/GK12/Activities/ACT_EnvironStudies/ENVIRON_68_SoilAndErosion/SoilAndErosion.html

Idaho museum of Natural historyhttp://imnh.isu.edu/digitalatlas/teach/lsnplns/eroscalp.htm

Food and agriculture organization of the United Nationshttp://www.fao.org/docrep/t1765e/t1765e0t.htm

about.comhttp://geography.about.com/od/physicalgeography/a/erosion.htm

Internet encyclopedia of sciencehttp://www.daviddarling.info/encyclopedia/O/oxbow_lake.html

EARTH SYSTEMS

here today, gone tomorrowthe effects of erosion


study guide for studentserosion is all around us. Erosion is part of a three-pronged process: Weathering—Erosion—Deposition. Weathering is the breaking down of solid rock into much smaller particles called sediment. Erosion refers to the movement of this sediment from one place to another. Deposition occurs when the sediment settles on a stable surface.

Weathering, erosion and deposition typically occur over long periods of time. It took nature millions of years to grind mountains down into rubble and carve valleys into vast plains. However, topsoil, the fertile layer of soil that plants require to grow, can be eroded very quickly, sometimes overnight during a flood or during one season of heavy rains. Soil erosion is a big concern to land managers, farmers, gardeners, real estate developers and others, so it’s important to understand how erosion works and how it can be prevented.

erosIoN Is CaUsed by severaL major aGeNTs:

Water

Water is erosion’s most important agent. Water erodes most commonly as running water in streams. The faster it moves, the larger the objects it can pick up and transport. This relationship is known as erosion velocity or speed. Erosion by streams causes valleys, waterfalls, flood plains, meanders (curves or bends in a stream or river) and oxbow lakes.

You’ll want to know what oxbow lakes are. The largest natural oxbow lake in North America is right here in Arkansas, Lake Chicot in the southeast corner of the state. Oxbow lakes are U-shaped bodies of water located in a former meander (curve) of a river. Originally, the meander was shaped like an almost-full circle. Eventually, the river cut through the narrow neck to shorten its course, depositing silt and sand. That blocked the meander from its main channel und over time, it became a separate lake. The river eventually moved farther away as the result of yet more–you guessed it—erosion.

Continued next page


Page 2 EARTH SYSTEMS • Here Today, Gone Tomorrow: Study Guide

Erosion Velocity

The greater the speed with which the water moves, the larger the objects that can picked up and transported.

In addition to running water, raindrops, standing water and groundwater lead to erosion. Rain drops create a type of “splash erosion” that moves tiny particles of soil. Heavy rains can sometimes cause mudflows or mudslides, which are rapid downhill movements of a mixture of water, rock and soil. Water puddles collecting on the surface of soil erode as they move toward tiny rivers and streams in a process called “sheet erosion.” And groundwater causes chemical weathering. This is a type of erosion where carbon dioxide breaks down certain rocks such as limestone. These broken-down rocks are then carried away in the water.

Wind

Wind picks up the finest particles—organic matter, clay and loam—and carries it many miles. Many centuries ago, it brought those fertile sediments from the outer perimeters of glacial areas to North Africa and Europe, allowing for the build-up of fertile soils and highly productive agriculture in those countries. Today, wind erosion occurs almost always in the desert. Its most spectacular forms are dunes, mounds of more or less sterile sands that move as the wind takes them. Wind erosion reduces the soil’s capacity to hold moisture and nutrients, making the environment drier.

Ice erosion is actually more powerful than water erosion, but much less common so it hasn’t accounted for the greatest amount of erosion on the earth’s surface. Plucking occurs when water enters cracks under the glacier, freezes and expands, breaking off pieces of rocks that are then transported by the mass of ice. Abrasion cuts into the rock

under the glacier, picking up pieces of rock like a bulldozer and smoothing and polishing the rock surface.

Wave erosion is an awesome display of natural forces. Large storm waves can exert 2,000 pounds of pressure per square foot. The sheer energy of the wave movement, combined with the chemical content of the water, leads to the erosion of rock along the coastline.

Human activities, particularly agricultural practices and mining, represent an indirect, but leading cause of soil erosion. Tilling and plowing as well as grazing animals leave topsoil loose and barren of any anchor plants, which could hold it in place. Strong winds or heavy rains can pick up particles of topsoil and carry them away, leaving unfertile weathered rock behind. Without fertile topsoil, plants can’t grow. Without plants, we have no agriculture. Without agriculture, we don’t have enough food to feed the world’s population.

The erosion of topsoil by water, wind and human activities can be prevented or at least lessened. Here are some possibilities:

Amending the soil: Adding organic matter or mineral applications (lime, gypsum, etc.) improves soil texture and structure, making the soil more

resistant to erosion.

Increasing plant cover: Crops can be planted more closely together or cover crops can be planted along with food crops to bind more soil

to a broad root system. Once anchored in this

manner, soil particles cannot be easily eroded by wind or water.

Increasing the roughness of the soil surface: This technique is often

used in flat areas prone to strong winds and storms. Large clods of soil are left on the soil surface or built into ridges perpendicular to the direction of the prevailing winds. Think of them as wind breakers that slow down the wind speed. A variation of this method is leaving crop


EARTH SYSTEMS • Here Today, Gone Tomorrow: Study Guide Page 3

weathering the breakdown of material into smaller and smaller pieces by mechanical or chemical means.erosion transportation of soil and rock by wind, water, gravity and ice.deposition the dropping of sediment from wind or water.

residue in the fields which also function as a type of barrier to strong winds.

Building wind breaks: Strategically planted, trees or shrubs can form hedges that cut the speed of wind, diminishing erosion.

Protecting and expanding wetlands: Wetlands serve to slow water flow and filter out sediments.

Minimize tilling: Extensive or deep tilling destroys soil structure by diminishing soil cohesion. It eliminates the air and water pockets as well as the living organisms that contribute to soil health so that soil particles become more susceptible to erosion by wind and water.


here today, gone tomorrowEARTH SYSTEMS

Aclass

assignment

ESS. 8.8.8 Demonstrate an understanding of the agents of erosion: gravity, water, animals, ice, etc.

1. Defineerosion:

2. what are the main agents of erosion?

1. ________________________

2. ________________________

3. ________________________

4. ________________________

5. ________________________ Take it Home

Visit your local track after school today. Walk with a parent, sibling or friend.



Aclass

assignment

answer key

1. Defineerosion:

Transportation of soil and rock by wind, water, gravity and ice

2. what are the main agents of erosion?1. Water

2. Erosion velocity

3. Wind

4. Ice

5. Human activities



Bclass

assignment

ESS. 8.7.10 Describe ways human beings protect themselves, others and their property from adverse weather conditions.

1. should people care about soil erosion? why?

2. explain how erosion might cause problems for farmers.

Take it Home




Bclass

assignment

answer key

1. should people care about soil erosion? why?This is a question of opinion and answers will vary.

2. explain how erosion might cause problems for farmers.Answers may vary but might include discussion of topsoil erosion, soil texture etc.



Cclass

assignment

ESS. 8.8.8 Demonstrate an understanding of the agents of erosion: gravity, water, animals, ice, etc.

1. Compare and contrast water and wind erosions.

2. describe why farmers might be concerned with soil erosion.

Take it Home




Cclass

assignment

answer key

1. Compare and contrast water and wind erosions. Both are types of erosion that can move large quantities of soil, sediment and rock. Water erosion of course carries the sediment, rock etc. by water, in lakes, streams, rivers or oceans. Wind erosion can pick up even the finest particles of organic matter such as clay and loam and carry it many miles. Wind erosion reduces the soil’s capacity to hold moisture and nutrients, making the environment drier.

2. describe why farmers might be concerned with soil erosion. Answers may vary but might include discussion of topsoil erosion, soil texture etc.

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