Overview

Grade: 4th

Topic: Earth Science

Standard:

• 4.ESS.1: Earth’s surface has specific characteristics and landforms that can be identified.

• 4.ESS.3: The surface of Earth changes due to erosion and deposition

In this lesson students will watch a streams table video, to learn the background, then investigate erosion through experiments.

Format

• Video & Questions for students

• Activity for students

• Quiz

Materials

• Student worksheet google doc

• Laminated target (or put target in ziploc bag)

• Eye dropper (or a plastic cup with a small hole punched in the bottom)

• Cup with water

• Handful of soil or sand

• Part 2: Dead leaves or shredded paper

• Extension activity: Popsicle stick or pencil (to use as fencing)

• Paper towels for cleanup

Background

Erosion is a naturally occurring process. Erosion has given us some of our most beautiful landscapes. There are beautiful erosion formations such as the Grand Canyon and Bryce Canyon, Utah. Erosion is the loosening, transportation, and relocation of soil particles from one place to another. Erosion occurs primarily due to the action of wind and water. The rate and extent of erosion are determined by soil type and condition, slope of the land, plant cover, land use, and climate. Erosion does not occur only on wilderness landscapes, and the effects are not always positive, especially when you are talking about productive topsoil. Landslides, can bury towns and claim thousands of lives. Streams or rivers loaded with eroded soil can turn sources of clean drinking water into major health hazards.

Water erosion includes raindrop splash, sheet erosion, rill erosion, gully erosion, and slumping or mass erosion. Raindrop splash is the most obvious on bare ground during a torrential rainstorm. The raindrops strike the ground and upon impact break soil particles apart, splashing these particles into the air. The impact of raindrops can be lessened by plant cover. Plants break the fall of the raindrops and allow for water infiltration or percolation.

Sheet erosion is the washing away of a thin surface layer of soil over a large area of land. Because sheet erosion occurs evenly, it is generally not obvious until most of the topsoil is removed.

Rill erosion may be noticeable on sloping bare ground after a rainstorm. Water forms small, well-defined channels that carry soil away from the sides and bottom of these channels. The rills of channels erode more soil as they move downslope and increase in size. When rills become large, the process is called gully erosion. This severe form of soil erosion removes tons of soil from the sidewalls and bottom of the gully.

Streambank erosion (and similarly, coastal erosion) is the cutting away of the banks by water. It is generally a slow process which represents the normal situation occurring along most streams. It is most active during floods when the amount and velocity of water are the greatest and when the bank soils are submerged under water and saturated.

Erosion and Farmland To control erosion, plant cover is usually the best solution. But to grow our food farmers make furrows in the land for row crops. A farmer can use a variety of methods to “keep soil in its place.” A farmer may plant his or her crops around the curve of a hill rather than up and down the hill, this is called contour planting. Plowing will also be done on the contour. Farmers may also build terraces. Terraces are wide ridges that go around a hill to prevent water from rushing down the hill too fast. On steep hillsides, rather than clear the area for cropland, farmers will maintain the area in forest and grass. Water always runs downhill, so farmers do not plow in low areas where water collects; instead they maintain low ditch areas as grassed waterways. Soils susceptible to wind erosion should be kept covered with some kind of vegetation. If this cannot be done year-round, a windbreak of trees and shrubs may be planted. Windbreaks are rows of trees planted to slow down the wind and prevent soils from blowing away in the wind.

Lesson

Activity 1: Video Introduction & Questions

Watch a 10 minute stream table video. The video shows the way the table works, how rivers are dynamic systems, the creation and destruction of landforms, and showcases erosion and deposition.

Have students answer the questions on the student handout as the video progresses. There are points throughout the video for you to pause the video. This to allow the students to answer the questions.

Activity 2: Targeting Erosion - From Ag in the Classroom

Students will be able to demonstrate rain drop splash (splash erosion) and determine its impact on bare soil, ultimately being able to visually identify types of erosion.

Teacher Preparation

1. Print and laminate targets, or put targets in ziploc bag.

2. Divide the class into groups, or have them work individually.

3. Give each group/individual a target, eyedropper, a small container of water, a small amount of soil, and a few leaves or shredded paper.

Activity: Part 1

1. Instruct student to put enough soil (about ½ teaspoon of dry soil) in the center of their target to just cover the center circle/bullseye.

2. Fill the eyedropper with water.

3. Hold the eyedropper about 18 inches (or 46 cm) above the soil sample.

4. Drop 5 drops of water directly onto the soil sample. If a drop misses the soil, continue until 5 drops hit the soil.

5. Record the number of water “splashes”—drops containing soil—in each zone.

6. Complete the graph to show your results.

Activity: Part 2 - plants

1. Clean the target and prepare it with soil to repeat the experiment.

2. Cover the soil with some leaves or shredded paper. This represents plants covering the bare soil.

3. Ask students to make a hypothesis about the amount of erosion

4. Hold the eyedropper about 18 inches (or 46 cm) above the soil sample and repeat the 5 drops hitting the soil.

5. Record the number of water “splashes”—drops containing soil—in each zone.

6. Ask the students to write a paragraph comparing the erosion with and without plant cover.

Wrap Up

Set up a Q&A time for your students with your county's Soil and Water Educator. Contact.

Assessment

Quiz- google forms 10 questions, all multiple choice.

Extensions

Reading

These readings are free with registration on ReadWorks, a nonprofit that provides Common-Core-aligned readings. All readings include comprehension questions.

The Forces that Shape Rocks (article a day set). Includes:

• Time, Weathering, and Erosion Shape Our World

• Physical Weathering at Work

• When Water Moves Sediments

• Sediments in the Wind

• Chemical Weathering of Rocks

• How the Hoodoos Formed

Questions

Questions? Please contact your county SWCD educator