GRADE: Third

CONTENT STANDARD: Earth and Space Science

CONTENT TOPIC: Geology/Earth Structure

CONCEPT: Rocks and soil move through a continuous cycle.

CONTENT OBJECTIVE: 3L5.00 To understand the rock-soil cycle

INSTRUCTIONAL OBJECTIVES: The learner will:

5.01 understand the rock-soil cycle.

I. Discuss the rock-soil cycle
II. Define and discuss the three layers of soil

TN COMPONENT OF SCIENCE: Habits of Mind

TN GOAL:

To enable students to demonstrate ways of thinking and acting inherent on the practice of science; and to exhibit an awareness of the historical and cultural contributions to the enterprise of science.

HISTORICAL AND CULTURAL PERSPECTIVE - The knowledge and processes of science have evolved over time as an approximation of truth within cultural contexts.

3.1c The desire to understand the natural environment and to predict the course of natural events is universal.

BENCHMARK: Curiousity and interaction with the environment compel people to question and explain events that influence their lives.

TIME REQUIRED:

Four instructional periods

Several samll pieces of sandstone, colored chalk, chalkboard, pictures of Grand Canyon, large plastic jars, coffee cans with lids (1 per 2 students), one glass jar, water, soil sample

Today, class, we are going to discuss the rock-soil cycle. We are going to learn about the three layers of soil. We will also discuss how soil is made.

Raise your hands if you have been to the mountains. Did you notice rocks at the bottom of the mountains? (The teacher should sketch a mountain scene on the board.) (Pointing at the mountain) Mountains are made of hard, solid rock. How many of you think that a mountain will last forever? (response) (Teacher needs to draw pebbles at the bottom of the mountain.) Look at these small pebbles at the bottom of this mountain. Where do you think they came from? (the mountain) The mountain is changing. It is being broken down into tiny bits and pieces. After a long period of time, these small pieces of rocks will become soil.

Raise your hand if you can think of something that would be strong enough to break a mountain into smaller pieces. (response, frozen water) (Draw drops of rain and make cracks in the mountain. Sketch boulders pebbles and rocks falling off.) Water that seeps into the cracks freezes and makes the cracks bigger and bigger until they split into pieces. The breaking of rocks into smaller pieces is called weathering. Can you think of another type of weathering? (wind) (Teacher needs to draw the wind and show small particles falling.) Yes, the wind and water break down mountains and rocks into smaller and smaller particles that settle on the earth as soil. Did you realize that plants can also weather or break down rocks? How do you think this can be? (The teacher should take the class outside to show examples of strong tree roots breaking sidewalks and curbs.) Some plants grow in soil that has collected in the cracks of rocks. The plant roots push on the rocks as the plants grow.

Imagine a shrub or tree growing in a crack on this mountain.(Refer to mountain drawing on the chalkboard. Add sketch of shrub or tree to drawing; show roots breaking apart the rock.)

Animals and even people can change rocks. Animals make places for weathering to happen. For instance, some animals make tunnels in the ground which loosens rocks and soil. Can you think of some examples of animals which build tunnels? (ants, rodents, earthworms). Their tunnels allow air and water to move deeper into the ground. (Sketch tunnels in the chalkboard mountain drawing.)

People also change rocks. What examples of this can you think of? (Listen to student responses.) People use machines to break rocks. We also dig tunnels and build roads through rocks. People build houses or statues out of rocks. Workers break the rocks into smaller pieces to use on buildings.

Ask students to jot down the definition of weathering in their own words. They should also list ways that rocks are changed.

Soil is made from pieces of broken rocks and minerals. It takes a long period of time to make soil. Nature makes about two and a half centimeters (1 inch of soil) approximately every 500 years.

1. The teacher can show how water can cause rocks to crack by doing the following: Fill a glass jar with water and place jar in freezer. The glass will be cracked because when it froze, it expanded or pushed out. The water became larger than the jar. Water in the rocks pushes out when it freezes thus causing the rocks to break.

2. Students compare different rocks and their textures after they have been weathered. Students take different kinds of rocks together in a can and shake for several minutes. Tell students to take tops off of can and ask them to tell you how the rocks look different.

3. Research rock collecting. Students may bring rock collections from home and they may begin new collections.)

Write a paragraph explaining the rock soil cycle, including some natural soil creators and some man-made soil makers. (Teacher needs to set a time limit of 15 minutes.)

weathering subsoil
mountain pebbles
soil boulders
rock particles
mineral sedimentary rock
topsoil

This is the time this file has been accessed since 05/18/97.

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