Fourth Grade - Science - Lesson 14 - Geology
 

Objectives

Demonstrate how, according to plate tectonic theory, folded mountains are formed at collision boundaries.

Identify a horst and a graben in a model of fault block mountain formation.

Describe how one might go about exploring the Marianas Trench.

Identify four types of mountains and match each to a description of how it was formed.
 

Materials

Map of mountain ranges for transparency

Kinds of mountains for transparency

Pictures of mountains and rift valleys from Suggested Books

U.S. map

A piece of aluminum foil 3-4 feet long, three cardboard boxes of the same size (boxes containing jello, ziplock bags, tissues are all suitable)

Mountain building worksheet (attached)
 

Suggested Books

Baker, Wendy and Andrew Haslam. Make It Work! Earth. New York: Macmillan, 1992. Simple modeling clay models of fold and fault-block mountains are found on page 24.

Catherall, Ed. Exploring Soil and Rocks. Austin, TX: Steck-Vaughn, 1990. Describes the four types of mountains and includes a demonstration with handkerchiefs for the different Earth layers. Also contains a color photo of the Black Hills (dome mountains) and a diagram of how a rift valley forms.

Farndon, John. How the Earth Works. Pleasantville, NY: Reader's Digest, 1992. On page 71 there is a step-by-step model demonstration of how a horst and a graben (rift valley) are formed.

Ganeri, Anita. Earth Science. New York: Dillon Press, 1993. Explains the formation of fold and block mountains with clearly labeled diagrams and photos of each.

Lye, Keith. Mountains. Morristown, NJ: Silver Burdett, 1987. Excellent diagram of what takes place at a collision boundary as well as many color photos of various types of mountains.

Parker, Steve. The Earth. New York: Marshall Cavendish, 1993. On page 26 there is an especially good discussion of how the Earth's crust bends, folds and breaks. Also contains a color photo of the Sierra Nevadas.

Silver, Donald. Earth: The Ever-Changing Planet. New York: Random House, 1989. Excellent illustrations of mountain building including the four types of mountains. Also contains an illustration of the Himalayas that corresponds to the shapes created with aluminum foil.

Zoehfeld, Kathleen. How Mountains Are Made. New York: HarperCollins, 1995. Tackles complicated phenomenon with simple illustrations and text. Part of the Let's-Read-And- Find-Out-Science series. Mountain formation is especially well addressed.
 

Procedure

Ask: If you were orbiting in the Space Shuttle looking back at Earth, do you think the Earth's surface would look flat and smooth like the skin of an apple? (No, it is bumpy and wrinkled. The Earth has mountains, hills, valleys and canyons.) Show the students the mountain ranges transparency. Point out that mountains are found on every continent including Antarctica which is not shown on this map. Remind them that, although they cannot see them from space, there are also mountains and canyons beneath the Earth's oceans. Ask: Are there some underwater mountains that are so tall they reach the surface of the ocean? (the island of Surtsey and the Hawaiian Islands) Ask: How were these mountains formed? (They are volcano mountains, formed by repeated eruptions and lava flow.) Have the students name a few volcano mountains (for example, Mt. St. Helens in Washington State, Mt. Fuji in Japan, Mt. Kilimanjaro in Kenya, Africa).

Tell the students that mountains are also formed in other ways. When geologists study mountains, they classify them according to the way they were formed. Show the students the kinds of mountains transparency. Point out the volcanic mountain and then the dome mountain. Tell the students that some mountains are formed by magma pushing up from beneath the surface. Unlike a volcanic eruption, the magma does not flow or shoot out a vent as lava. Instead, the magma builds up under the Earth's crust and pushes it up like air pushing on the inside of a balloon, making it inflate. The magma has so much pressure behind it that it pushes up a bulge or a dome in the Earth's crust and makes a mountain. Tell the students that over millions of years the magma beneath a dome mountain hardens into a solid core. Show the students pictures of the Black Hills from Suggested Books as examples of dome mountains. Locate the Black Hills of South Dakota on a U.S. map.

Tell the students that another way mountains are formed has to do with collision boundaries. Ask: What is a collision boundary? (It is where two plates are pushing against each other.) Ask: What do you think might happen when two plates carrying layers of the Earth's crust and mantle are pushed and squeezed together? (Accept all answers.) Lay a long piece of aluminum foil across some desks and identify it as the Earth's crust. Have two students come forward and stand at each end of the foil. Identify the students as the forces behind crustal plates. Have them place their hands palms down on the corners of the foil and then push very slowly toward each other. The foil will crumple up in folds and mounds. Ask: What happened to the surface of the Earth? (It was pushed up in bumps or mountains.) Tell the students that mountains formed this way are called folded mountains. Ask: Why do you think they are called folded mountains? (because the Earth's crust is folded or bent) Tell the students that another way to picture folded mountains is to imagine what happens when you push together the ends of a rug or a dish towel. The more you push the ends together, the more it wrinkles and crumples into folds. Ask: What are the low places in between the mountains called? (valleys) Tell the students that the tallest mountains on land, the Himalayas, are folded mountains. Locate India and the Himalayas on the mountain ranges transparency. Tell the students that the Himalayas are also the newest folded mountains. About 45 million years ago, the Indo-Australian plate and the Eurasian plate slammed into each other. The ocean floor between the two land masses was pushed up into mountains. They are still being pushed up today. The Himalayas are pushed up two inches higher every year. Point out that the Rockies and the Appalachians in the U.S., the Andes in South America and the Alps in Europe are all folded mountains. Show the students pictures of some of these folded mountains from Suggested Books. Tell them that geologists have a name for the movement of plates that builds a mountain chain. It is called orogeny (oh-RAH-juh-nee). Write this word on the board. Tell the students the word comes from the Greek word oro which means mountain and from genesis which means creation. Orogeny is the creation of mountains.

Point out on the kinds of mountains transparency, the fourth kind of mountain: fault block mountain. Ask: What is a fault? (a deep crack in the Earth at the boundary of two plates) Tell the students that sometimes rocks are brittle and will not fold or bend. Instead they crack. Line up the cardboard boxes end-to-end on a desk and tell the students you are going to play at fault block mountain building. Ask the students to imagine that the tops of the boxes are the Earth's surface. Pressure from movement of plates causes the surface to crack into huge blocks at fault lines. Tell them that a block on one side of a fault might be slowly pushed up (slowly raise the center block). Another might slip down or tilt (demonstrate this with the boxes). Tell the students that when a block is pushed up, it is called a horst. When it slips down, it is called a graben. Demonstrate a horst and a graben with the boxes and ask the students to identify each. Tell them that a simple way to remember which is which: you have to hoist yourself up on a horst. Tell the students that when two pieces of the crust are pushed up and the one between them sinks, that is, when a large graben lies between two horsts, it is called a rift valley. Demonstrate this with the boxes. Show the students pictures in Suggested Books of block mountains (Sierra Nevadas) and of rift valleys (The Great Rift Valley in East Africa, Death Valley in the U.S., the Rhine River Valley in Europe).

Ask: Does anyone know where the deepest valley on the planet can be found? (Accept all answers.) Tell the students that this valley is much deeper than the Grand Canyon. It is deeper than Mt. Everest is tall. It is nearly 7 miles deep and 600 miles wide. Tell the students that this deep valley is at a collision plate boundary under the Pacific Ocean and is called the Marianas Trench. Write this on the board and locate the Marianas Trench on the mountain ranges transparency or a world map. Ask: How do you think scientists discovered how deep the Marianas Trench was? Do you think anyone has ever gone to the bottom of the Marianas Trench? (Accept all answers.) Remind the students that as one goes deeper and deeper in the ocean, it becomes very dark. There is no light because the sunlight cannot reach into the depths. The water is very, very cold. As one goes deeper, the water presses in and can crush a person. Ask: If you were going to explore the Marianas Trench, how would you do it? What would you need to go so deep in the ocean? What do you think you would find down there? Do you think there are living things at the bottom of the Marianas Trench? What do you think they look like and how do they survive? Ask the students to write a description of how they would go about exploring the Marianas Trench and what they think they would find.

Possible Homework

Have the students complete the Mountain Building worksheet (see attached).

Objectives

Observe salt crystals with a hand lens.

Describe differences in rock samples.

Test rock samples for hardness and chart the results.
 

Materials

Several sheets of black construction paper, table salt, hand lenses

Pictures of mineral crystals from Suggested Books

For each group of five students: five rock samples for testing, a hand lens, penny, a nail, paper scraps for labeling rocks, paper for recording results
 

Suggested Books

Baker, Wendy and Andrew Haslam. Make It Work! Earth. New York: Macmillan, 1992. Pages 26-28 contains color photos of rock samples and minerals in the 1-10 hardness scale. Also includes an activity to grow limestone stalactities on a string.

Catherall, Ed. Exploring Soil and Rocks. Austin, TX: Steck-Vaughn, 1990. Good close-up views of granite and the layers of sedimentary rock in a limestone cliff.

Curtis, Neil and Micheal Allaby. Planet Earth. New York: Kingfisher, 1993. Pages 30-33 contain illustrations of rock-forming minerals and examples of the three kinds of rocks.

Farndon, John. How the Earth Works. Pleasantville, NY: Reader's Digest, 1992. Includes small color photos of rock samples but there are several examples of each kind of rock.

Parker, Steve. Science Project Book of the Earth. New York: Marshall Cavendish, 1986. On page 22 is a close-up photo of limestone and dolomite as well as color illustrations of granite, obsidian, marble and slate among others.

Peacock, Graham and Jill Jesson. Science Activities: Geology. New York: Thomson Learning, 1995. Contains other tests that can be done on rocks and a grow-your-own crystals activity. On page 24 there is a collection of color photos identifying various stone building materials.

Pellant, Chris. The Earth. New York: Dorling Kindersley, 1992. Pages 20-21 include beautiful color photos of rocks and minerals. There is also a photo line-up of the softest to hardest minerals from talc to diamonds.

Ritter, Rhoda. Rocks and Fossils. New York: Franklin Watts, 1977. A very simple description of the formation of three kinds of rocks plus black and white photos and illustrations of rock samples and formations.

Shuttlesworth, Dorothy. The Story of Rocks. Garden City, NY: Doubleday, 1966. Identifies rocks as "fire-formed" (igneous), "second hand" (sedimentary) and "born of heat and pressure" (metamorphic). Contains a description of the hardness test for rocks and some examples of the varying degrees of hardness.

Snedden, Robert. The Super Science Book of Rocks and Soils. New York: Thomson Learning, 1995. Good section on rock formation with photo of rock samples.
 

Website

http://www.galaxy.einet.net/images/gems/gems-icons

Smithsonian Museum of Natural History website features color photos and information about their gems and minerals exhibits.
 

Fourth Grade - Science - Lesson 15 - Geology
 

Teacher's Note

If possible, have students bring in rock samples for testing. Remind them that asphalt and cement pieces are manmade and should not be tested along with natural rock.
 

Procedure

Tell the students that at the end of the lesson, you are going to ask them a question. The question is: Do rocks ever change? Remind them that plants and animals change as they grow. Some insects go through metamorphosis and change form. Have someone name an insect that goes through metamorphosis (caterpillar/butterfly, ant, bee, beetle). Remind them that what you would like to know is: Do rocks ever change? Write the question on the board.

Tell the students that to find the answer, they might need to know what rocks are made of. Tell them that, like everything else in the world, rocks are made of chemicals. The chemicals that rocks are made of are called minerals. Write this word on the board. Tell the students that if they looked at a rock under the microscope, they would see tiny mineral crystals. Some crystals are big enough to see without a microscope. Sprinkle a small amount of table salt or kosher salt on several pieces of black construction paper and distribute them throughout the room along with hand lenses so students can see the crystals. Have a student come to the board and draw the shape of a salt crystal. Tell the students that rocks are made of different combinations of mineral crystals. If available, show the students pictures of mineral crystals from Suggested Books. Point out that crystals come in various shapes but all have flat sides or faces like the salt crystal. The mineral crystals are packed together in rocks.

Hold up two rock samples of distinctly different colors and textures. Ask: How are these two rocks different? (color, texture, dull or shiny, weight) Tell the students another way to compare rocks is to test them for hardness. Some rocks are hard and some are actually soft. Geologists rank rocks on a hardness scale from 1 to 10. Rocks that get a 1 are very soft. The hardest rocks get a 10. Divide the students into groups of five and tell them that today they will be testing rock samples for hardness. First they will need specific tests. Ask: If you can scratch a rock with your fingernail, is it soft or hard? (soft) Tell the students that rocks that can be scratched with a fingernail get a rank of soft on the hardness scale. Write fingernail test-soft on the board. Point out that rocks that can be scratched with a penny are a little bit harder. They get a medium-soft on the hardness scale. Write penny test-medium soft on the board. Point out that a rock that cannot be scratched by a fingernail or a penny but can be scratched with a nail gets a hard on the hardness scale. Write nail test-hard. Tell the students that any rocks that cannot be scratched, even with a nail, are ranked as very hard. Write no scratches-very hard on the board. Ask the students to label their rock samples 1 through 5 and put them through the hardness tests.

Make a chart and record the results. Ask them to include in the chart a short description of the rock--its color, texture and anything else they observe about it. Distribute the rock samples and test materials. When the rock testing is finished, have one or two groups report on their results. Remind the students that last time they learned how geologists classify mountains. Ask: What are the four kinds of mountains? (volcanic, dome, folded and fault block) Remind them that mountains are classified according to how they were formed--their orogenies. Tell the students that rocks are also classified according to how they were formed. Rocks that are formed from cooling lava or magma are called igneous rocks. Write igneous on the board. Tell the students that igneous rocks are also called fiery rocks to describe how they were formed. Ignit is the Latin word for fire and where we get the word ignite. Ask: What igneous rocks did we see pictures of (samples of) in studying volcanoes? (obsidian, pumice) Ask: What kind of rocks are volcanic mountains made of? (igneous) Ask: What about dome mountains? What kind of rock would you expect to find at the core of a dome mountain? (igneous) Why? (because the magma pushed up the mountain and then cooled into hard rock) Tell the students that granite, a very hard igneous rock, is used to for buildings and monuments around Baltimore.

Tell the students that the second kind of rock could also be called "second-hand" rock. Write sedimentary on the board. Sedimentary rock gets its name from the Latin word sedo which means settle down. Tell the students that sedimentary rocks formed when sand and debris settled down in layers at the bottom of ancient oceans. Over millions of years, the top layers pressed down on the lower layers, squeezing out the water, until the tiny grains were cemented together into sedimentary rock. Later, plates crashed together at collision boundaries and made mountains. Ask: What kind of mountains? (folded) Remind the students that ancient sea beds were pushed up to be the tops of mountains when the Himalayas formed. Ask: What kind of rock then might you find at the top of a folded mountain like Mt. Everest? (sedimentary rock)

Tell the students that the name of the third kind of rock might remind them of butterflies. It is metamorphic rock. Write metamorphic on the board. Ask: Why might this name remind you of butterflies? (It sounds like metamorphosis. Caterpillars go through metamorphosis to become butterflies.) Tell the students that metamorphic comes from the Greek words meta which means change and morphe which means form. Metamorphic rocks have changed form. Heat and pressure inside the Earth changed their mineral crystals into new minerals. It can happen when magma is forced up into cracks and heats the surrounding rock to such high temperatures that the rock is changed. It can also happen when pressure of heavy mountains on top of rock is so great that it works like heat to change the rock's minerals. The changed rock is metamorphic rock. There is one kind of pretty white metamorphic rock that is used all over Baltimore to make front steps. Ask: Does anyone know what kind of metamorphic rock that is? (marble) Tell the students there is another kind of gray metamorphic rock that is used to cover roofs of houses. Ask: Does anyone know what this metamorphic rock roofing material is called? (slate)

Review the three kinds of rock and how each is formed. Remind the students of the question you asked at the beginning of the lesson. Ask: Do rocks ever change? (Yes, metamorphic rock changes from one kind of rock to another.) Tell the students that next lesson they will learn about another way that rocks change.
 

Possible Field Trips

Ask a university geologist or rock hound to give a tour of local buildings in Baltimore to find examples of the three different kinds of rock.

Redlands Genstar is a company that offers special tours of their quarries in Baltimore County. The contact person to arrange tours is David Whitehurst, 300 E. Joppa Road, Towson, MD 21286 (410) 847-3211.

The Smithsonian Natural History Museum in Washington, D.C. has a newly expanded geology exhibit that includes famous gemstones such as the Hope Diamond as well as other mineral displays and truly impressive fossil exhibits, including dinosaurs!

The Natural History Society of Maryland has a collections of rocks and fossils among other fascinating things at 2643 N. Charles St., (410) 235-6116.
 

Fourth Grade - Science - Lesson 16 - Geology

Glacier demonstration adapted from How the Earth Works by John Farndon
 

Objectives

Describe how igneous, sedimentary and metamorphic rocks are formed.

Brainstorm ways eroding agents might move crumbled rock.

Observe and describe the effects of a miniature glacier.
 

Materials

Pictures of mountains, canyons, river valleys and glaciers from Suggested Books

Piece of chalk, white vinegar, a glass dish

A few hand-sized rock samples, dish of gravel or pebbles, dish of sand, dish with chalk powder

Pictures of examples of chemical weathering from Suggested Books

Ice cubes, piece of wood

U.S. map
 

Suggested Books

Farndon, John. How the Earth Works. Pleasantville, NY: Reader's Digest, 1992. Page 133 includes the glacier demonstration plus information on creeping ice.

Ganeri, Ann. Earth Science. New York: Dillon, 1993. On pages 26-27 there are pictures of V- shaped and U-shaped valleys and a glacier in Iceland.

Lye, Keith. Mountains. Morristown, NJ: Silver Burdett, 1987. Page 19 has photos of erosion by glaciation and erosion by wind and sand.

Markle, Sandra. Earth Alive! New York: Lothrop, 1991. Page 30 shows a rock arch formed by weathering; page 27 has pictures of a mountain in Yosemite sheared off by a glacier; pages 24-25 include two pictures of glaciers.

Parker, Steve. Science Project Book of the Earth. New York: Marshall Cavendish, 1986. Characterizing the forces of weathering and erosion, Parker writes, "Earth keeps making new mountains and valleys while the Sun-powered forces of erosion keep trying to flatten them." Pages 28-29 include a photo of Angel Arch in Utah shaped by wind and illustrations of U- and V-valleys.

Peacock, Graham and Jill Jesson. Science Activities: Geology. New York: Thomson Learning, 1995. Page 25 features erosion and weathering in the city. On page 26 there are two simple activities that demonstrate weathering and erosion.

Pellant, Chris. The Earth. New York: Dorling Kindersley, 1992. A two-page spread on 30 and 31 features glaciers and pictures of some examples of weathering.

Silver, Donald. Earth: The Ever-Changing Planet. New York: Random House, 1989. Pages 62- 65 give an indepth look at glaciers. Pages 66-67 include illustrations of desert rock formations caused by wind and sand.

Simon, Seymour. Icebergs and Glaciers. New York: Morrow, 1987. Wonderful pictures of glaciers and evocative text: "When glaciers move, they grind and crush everything in their path."

Snedden, Robert. The Super Science Book of Rocks and Soils. New York: Thomson Learning, 1995. Effects of chemical weathering are shown on page 13.

Taylor, Barbara. Earth Explained: A Beginner's Guide to Our Planet. New York: Henry Holt, 1997. Pages 10-11 contain a succinct description of weathering and erosion and three small illustrations showing examples of wind, water and ice erosion.
 

Fourth Grade - Science - Lesson 16 - Geology
 

Teacher's Note:  A few ice cubes for the glacier demonstration can be kept cold in a ziplock bag inside a thermal lunch bag

Procedure
Remind the students that last time they answered the question: Do rocks ever change? Ask: What kind of rocks are formed when igneous and sedimentary rocks change? (metamorphic rocks) Ask: Do you remember how igneous rock is formed? (from hardened magma or lava) Ask: How is sedimentary rock formed? (Sand and debris settles down in layers at the bottom of oceans. Top layers press down on the lower layers until the tiny grains are cemented together.)

Tell the students that there is another way that rocks change. It is called weathering. Write this word on the board. Tell the students that weathering over time crumbles rock, breaks it down into smaller pieces. Write ice, water, wind, and roots on the board. Tell the students that these are the crumblers and crack makers when it comes to rocks.

Ask the students to imagine a cement sidewalk in their neighborhood. Imagine that next to this sidewalk a small tree is growing. It stretches its roots under the sidewalk and pushes up until a small crack opens up in the cement. The tree root sneaks into the crack. As the root grows it pushes the sides of the crack wider and wider apart. Rain soaks into the crack and carries tiny bits of dirt with it. Then nights grow cold. The moisture in the crack freezes into ice. The ice expands and pushes hard on the sides of the crack until the crack becomes a spiderweb of cracks. In spring, some dandelion seeds are blown into the sidewalk cracks and settle into the soil that has collected there. They sprout and their roots push the cracks wider and wider. By summer a small piece of the cement is so loose that when someone walks by, they kick it into the gutter. After another winter of freezing and thawing, the sidewalk has crumbled. Many pieces are missing, washed away by heavy rains. Weathering has broken down the rock in the cement sidewalk.

Show the students a picture of a mountain from Suggested Books. Ask: Do you think an entire mountain could be broken down by weathering? (yes) Ask: How long do you think it might take for an entire mountain to crumble away? (Accept all answers.) Remind the students that the Himalayas are new mountains and are still being pushed up. The mountain range nearest to us, the Appalachians, is made up of old mountains. They have been weathered and worn down over many millions of years. Geologists have found that a mountain gets 3.5 inches shorter every 1,000 years. Draw a line 3.5 inches on the board. Tell the students that over time, physical weathering breaks rock down into smaller and smaller pieces from huge boulders to hand-sized rocks, to pebbles and gravel to sand to powder. Show the students samples of each (except the huge boulder).

Tell the students that another kind of weathering is called chemical weathering. Instead of cracking rock, chemical weathering dissolves rock. Acid from bacteria in the soil or acid rain falls on the rock and over time dissolves it. Show the students a piece of chalk. Point out that chalk is a soft sedimentary rock. It can be scratched with a fingernail. Demonstrate this. Show the students the bottle of vinegar and tell them that vinegar is an acid like the acid in soil or acid rain but is stronger. Pour some of the vinegar into the glass dish. Ask: What do you think will happen when I put this chalk made of soft rock into this strong acidic vinegar? (Accept all answers.) Drop the chalk into the vinegar. Ask the students if they have noticed chemical weathering on buildings, statues or gravestones in the city. Show them pictures of the effects of chemical weathering from Suggested Books. Tell them that mountains are effected by chemical weathering, too. After a few moments, remove what is left of the chalk from the vinegar. Ask: What happened to the chalk? (It is dissolved or eaten away by the acid in the vinegar.) Tell the students that acid in the soil or acid rain would take more time to dissolve rock.

Tell the students that you have a mystery to solve. The name of the mystery is: Case of the Disappearing Rocks. Ask: What do you think happens to the pieces of rock that crumble from mountains? Do they disappear? (Accept all answers and write them on the board.) Ask the students if they have ever heard the word erosion. Write this word on the board. Tell the students that erosion is the movement of crumbled rock from one place to another. Erosion is what shapes the surface of the Earth. Write water, ice, wind, gravity on the board. Tell the students that these are the eroders, the forces that move boulders, rocks, pebbles, gravel, sand and powder. Brainstorm with the students ways these eroders might move crumbled rock. Examples might include streams carrying it downhill or wind blowing sand. Tell the students that water, sand and wind can carve rock. Show the students pictures from Suggested Books of canyons and river valleys carved by water and windblown sand. Show the students a smooth pebble from the beach or a river bed. Ask: How do you think this pebble became so smooth? (It was tumbled round with other rocks and sand in moving water until all the rough edges were worn away.)

Ask: How could ice carve rock? (Accept all answers.) Tell the students that glaciers form in very cold parts of the world or on mountain tops. Glaciers are huge masses of ice. They can move very slowly or very quickly downhill. As they creep, they drag along rocks and scrape the ground beneath them. Show the students pictures from Suggested Books of glaciers. Take out an ice cube and dip it in the bowl of sand. Point out that this is a miniature glacier and the sand is like the rocks beneath it. Rub the ice cube in a circle on a piece of soft wood, occasionally redipping it in the sand. Students can help you with this process. Show the students the wood. Ask: What did the miniature glacier do? (It scratched the wood.) Ask the students to imagine an ice cube as big as the city of Baltimore creeping down a slope dragging stones beneath it. Ask: Do you think this glacier would be heavy? (yes, millions of tons) Tell the students that glaciers can gouge big grooves in rock. They can also polish rock until it is so smooth it reflects the light. Big glaciers can carve through valleys. A valley shaped like a V would be a U-shaped valley after a glacier moved through it. Tell the students that about 12,000 years ago during an ice age, enormous glaciers moved down from the north and covered a lot of what is now the northern U.S as well as Europe and Asia. These glaciers gouged out huge holes in the ground. When the glaciers finally melted, the holes filled up with water and became the Great Lakes. Locate the Great Lakes on the U.S. map.

Getting back to the disappearing rocks mystery, ask: What happens to the rocks that crumble from weathering mountains? (They are broken into smaller and smaller pieces.) Where do they go? (They are carried by eroders to other places.) Tell the students that next lesson they will track rocks from a mountain to find out where they might travel.
 

Possible Homework

If a mountain is 5,000 feet tall, about how long would it take for weathering to wear the mountain away. Remind the students that geologists estimate that a mountain loses 3.5 inches every 1,000 years.
 

Fourth Grade - Science - Lesson 17 - Geology

Sediment-making project adapted from Earth Science by Anita Ganeri
 

Objectives

Describe how flowing water erodes weathered rock, carrying it from mountains to oceans.

Describe why the oceans do not fill up with sediment.

Create a sediment mixture and observe how particles settle.

Describe what soil is.
 

Materials

Mountain to delta diagram for transparency

A pebble, a piece of cardboard

Ocean trench diagram for transparency

Three small buckets or containers (one containing gravel, one containing all-purpose sand and the third containing soil), scoops or spoons for each bucket, newspaper to catch any spills For each group of five students: clear plastic 2-liter bottle with cap, funnel, pitcher of water, newspaper
 

Suggested Books

Baker, Wendy and Andrew Haslam. Make It Work! Earth. New York: Macmillan, 1992. On page 31 is a photo of the stages of breakdown from rock to powder.

Taylor, Barbara. Earth Explained. New York: Henry Holt, 1997. Describes underwater landscape of mountains and plains and explains the subduction of sediment in deep ocean trenches. Ganeri, Ann. Earth Science. New York: Dillon, 1993. Ganeri's description of how a river flows is excellent.

Pellant, Chris. The Earth. New York: Dorling Kindersley, 1992. A section on rivers includes a model of a river from glacier-covered mountain to delta. Also includes a small picture of the Grand Canyon.

Silver, Donald. Earth: The Ever-Changing Planet. New York: Random House, 1989. "Night and day, year after year, rivers deliver tons of sediment from the land into the ocean waters." Silver's definition of sediment includes boulders as well as silt and clay. Pages 78-79 contain a wonderful illustration of "diving" plates.
 

Teacher's Note

All-purpose or concrete sand, readily available in hardware stores, is the best sand for sediment making. It has varying sizes of grains and so ultimately settles in distinct bands after a few days. Be sure the gravel has small enough grains to pass through the opening in the funnel. Fine-grained gravel is available in pet stores or pet departments (used in aquariums) and at gardening centers. Bottles with the flattest bottoms work best for observing the lowest layers.
 

Procedure
Remind the students that last lesson they were trying to solve the mystery of the disappearing rocks. Ask: What happens to rocks over time? (They are broken down into smaller and smaller pieces.) Ask: What do we call this process? (weathering) Remind the students that erosion is the movement of these pieces of crumbled rock from one place to another. Ask: Can someone name an eroder--something that moves crumbled rock? (water, glaciers, wind, gravity)

Show the students the mountain-to-delta transparency and a pebble. Point to the mountain and ask the students to imagine that the pebble broke off a large crumbling boulder on the mountainside. Trace the pebble's path on the transparency while telling its story. Tell the students that the pebble rolled down the slope and stopped near a pile of other pebbles. Then heavy rains came and washed the pebble down into a mountain stream. The pebble was carried by rushing water over a waterfall, down, down the mountain until the stream dumped its waters into a fast-moving river. The pebble tumbled over and over with other pebbles and rocks, sand and soil pushed by the current of the river. As the river snaked its way through a valley, its waters slowed a bit and some of the bigger rocks were dropped on the river bed. But the small pebble tumbled on for miles and miles. By now it was a smaller and smoother pebble than when it started its journey. Its edges had been worn away by the constant rubbing against other rocks and sand on the river bed. Where the river neared the sea, its current slowed. Rocks, pebbles, sand and soil settled to the bottom in layers, piling high until islands of sediment poked up through the river. The river split and flowed around the islands like fingers finally touching the sea. The pebble settled in the mud of the river delta. Then one day there was a terrible storm. Heavy rains filled the river to the tops of its banks. The whirling, racing water was brown with the mud it carried. As it reached the delta, the current cut new channels to the sea. The pebble was picked up by the river's flood waters and pushed out into the sea current. It tumbled down an underwater slope and stopped in a pile of other pebbles and seashells. Tell the students that every day streams and rivers carry tons and tons of sediment, like the pebble, from land to ocean.

Ask: What is sediment? (sand, mud, pebbles, rocks, dead plants, animals, their shells--anything that settles to the bottom) Tell the students that all kinds of weathered rocks are sediment. Remind the students that sediment on the bottoms of oceans or lakes is sometimes squeezed down and over millions of years, forms a kind of rock. Ask: What kind of rock is that? (sedimentary rock) Point out that in this way, weathered rock is recycled into sedimentary rock. Ask: If weathered rocks and mud are constantly being carried away from the land to the sea, why doesn't the ocean fill up with sediment? (Accept all answers.)

Tell the students that if they were able to go to the bottom of the Marianas Trench or other deep ocean trenches, they would see how sedimentary rock is recycled, too. Show the students the ocean trench transparency (see attached). Remind the students that when they studied collision plate boundaries, they learned that sometimes a plate dives under another plate. Tell the students that in deep ocean trenches, one plate moves beneath the other plate toward the Earth's mantle. Heat melts the rock into magma. Sometimes the magma rises and forces its way through the Earth's crust and shoots out a vent. Ask: What is magma called when it flows or shoots out of a volcano's vent? (lava) Remind the students that the lava hardens into igneous rock. In this way sedimentary rock from the ocean is recyled into new rock on land. New land is always being made by volcanoes and other mountain building and it is always being worn away by weathering and erosion. As one author put it, "Earth keeps making new mountains and valleys while the...forces of erosion keep trying to flatten them." Ask the question again: Why doesn't the ocean fill up with sediment? (because the sediment becomes rock again and is recycled in ocean trenches)

Show the students the three buckets and ask them to identify their contents. Ask: What is gravel? (small pieces of rock) Ask: What is sand? (even smaller pieces of rock) Ask: What is soil? (very small pieces of rock mixed with decaying plants and animals). Remind the students that soil is home to many living things, too. Ask: What living things make their homes in soil? (plants, insects, worms, burrowing animals such as moles and shrews, decomposers and bacteria) Point out that the three buckets contain weathered rock separated according to different sizes of grain from big gravel to medium-sized sand to fine-grain soil. Have the students create their own recipes for sediment using the contents of the buckets. As they fill the plastic bottles using funnels, remind them to leave half the space in the bottle for river water. Have each group pour water from the pitcher into the bottle and securely seal with the cap. By rolling the bottle across a desk, students can simulate the river current. Ask: What happens to the sediment? (It tumbles around and mixes with the water.) What happens if the water stops moving? Have the students put the bottles upright and observe what happens to the sediment. After several minutes, sand and gravel will settle to the bottom. Depending on how much soil was in the recipe, the water will remain murky for a while, like a river's waters after a storm. Ask: Once the water stopped moving, what ingredient of your sediment recipe tended to settle first? (gravel) How can you tell? (It is at the bottom.) Ask: What ingredient settled after that? (sand) What ingredient seems to be settling next? (soil or mud) Ask: Is there anything floating at the top? What do you think that is? (sticks, tiny pieces of bark, dried grass, seeds, etc.) Ask: Why do you think the gravel settled first? (Gravel has the biggest grains. The biggest and heaviest grains tend to sink more quickly and end up on the bottom first.) Ask: What has the second biggest grain in the sediment recipe? (sand) the third biggest? (soil) Ask: If the river in the bottle started rolling again and then stopped moving, would the sediment settle in the same order--biggest at the bottom? Ask the students to roll the river in a bottle again and observe in what order the sediment ingredients settle. Have a student come up and draw a bottle on the board with the sediment layers and label them.

Ask: How is weathered rock moved from the mountains to the ocean? (Flowing water of streams and rivers lifts it up and carries it.) Ask: When the water slows down and is not moving so quickly, what happens to the sediment? (It settles to the bottom.) Ask: What tends to settle to the bottom first when sediment settles? (The biggest and heaviest grains or particles tend to settle first when the water stops moving.) Have the students put the bottles in a place where they will not be disturbed. After several days of settling, the layers will be more clearly discernable.

Tell the students that soil on land is in layers, too. Draw a diagram of soil with three layers on the board and label them. Tell the students that at the bottom is a layer of solid bedrock. On top of the bedrock is a layer of subsoil. Subsoil is mostly pieces of rocks. On top of the subsoil is topsoil, soil that plants and animals live in. Topsoil has lots of nutrients in it from decaying material as well as minerals from weathered rocks. Plants use the nutrients and minerals to grow. Draw a diagonal line on the board and tell the students that it is the side of a hill. Ask: What do you think happens to topsoil when it is on a slope like this? Hold a piece of cardboard at an angle and pour some soil from the bucket on it until the soil begins to slip down the slope. Ask: What keeps soil from sliding down steep hillsides and washing away? (plants--grass, trees, bushes--cover the soil) Tell the students that plants form a mat or net with their roots that holds the soil and keeps it from eroding. Plants are erosion fighters. Ask: What do you think might happen if people cut down all the trees on a hillside? (Explain that cutting down all the trees is called clear cutting.) What might happen to the soil? (It could be eroded by water and wind.) If the topsoil is eroded--washed or blown away--what would be left? (Subsoil or bedrock) Will plants grow in subsoil or bedrock? (no) Ask: Do you think clear cutting is a good idea? Why or why not?

Fourth Grade - Science - Lesson 18 - Geology

Fossil making activity adapted from The Super Science Book of Rocks and Soils by Robert Snedden
 

Objectives

Describe how rock is recycled.

Hypothesize why sea animals might be embedded in rock at the top of the Himalayas.

Create a model of a cast fossil.

Sequence and describe the stages in the formation of a fossil.
 

Materials

Rock cycle diagram for transparency

Pictures of fossils from Suggested Books (or actual fossils if available)

An assortment of seashells, bones, nuts, leaves, and twigs

Plaster of Paris, mixed according to label directions in a plastic pitcher

For each group of five students: Playdoh or modeling clay, a shallow, plastic container larger than the largest seashell

Fossil formation worksheet
 

Suggested Books

Clifford, Nick. Incredible Earth. New York: Dorling Kindersley, 1996. Pages 12-13 include good photos of fossils and illustration of fossil formation.

Curtis, Neil and Micheal Allaby. Planet Earth. New York: Kingfisher, 1993. On pages 34-35 are illustrations showing how a fossil is formed.

Farndon, John. How the Earth Works. Pleasantville, NY: Reader's Digest, 1992. There are good pictures of fossils--ammonite, coral and sea urchin--on page 89.

Peacock, Graham and Jill Jesson. Science Activities: Geology. New York: Thomson Learning, 1995. On page 29 is a branching key to help young paleontologists identify some fossil sea animals.

Pellant, Chris. The Earth. New York: Dorling Kindersley, 1992. Pages 22-23 include color photos of fossils--fish, leaf and dragonfly--as well as a rather gruesome fossilized foot of a giant extinct bird.

Ritter, Rhoda. Rocks and Fossils. New York: Franklin Watts, 1977. Includes black and white photos of fossils such as a trilobite and a sea scorpion.

Silver, Donald. Earth: The Ever-Changing Planet. New York: Random House, 1989. The short section on fossils is excellent. Silver also discusses fossils found in places other than rock--tar pits, glacial ice and in amber.

Snedden, Robert. The Super Science Book of Rocks and Soils. New York: Thomson Learning, 1995.

Whitfield, Philip. Why Do Volcanoes Erupt? New York: Viking, 1990. Whitfield, a curator at the National History Museum in London, answers questions about earth sciences. Pages 36 and 37 include good color photos of plant and animal fossils.
 

Teacher's Note

Scallop, oyster and clam shells, as well as clean dry chicken or beef bones make good clay impressions for fossils. Plaster of Paris can be mixed in one plastic pitcher and passed from group to group for pouring into the mold. Hardening time is usually over an hour, so unmolding of fossils will have to take place later in the day.
 

Procedure

Review with the students how weathered rock is eroded and recycled. Show the students the transparency of the rock cycle (see attached). Ask: How does weathered rock become sediment? (Weathered rock--gravel, pebbles, sand, soil--washes into streams and rivers and is eventually carried to oceans.) Ask: Over time, what happens to the sediment? (It is compressed into sedimentary rock on the ocean floor.) Ask: How is sedimentary rock recycled into mountain building? (At some plate boundaries where plates are colliding, old sea beds of sedimentary rock are pushed up to build mountains.) Ask: What happens in ocean trenches? (Where one plate dives under the other, sedimentary rock is carried down near the mantle where it melts and becomes magma. The magma erupts through volcano vents as lava and hardens into igneous rock, building a volcanic mountain.) Ask: Over time, what happens to the new mountain rock? (The new mountain rock is weathered and eroded.) Point out to the students that this recycling of Earth's rocks is called the rock cycle.

Tell the students that now that the mystery of the disappearing rocks is not a mystery anymore, you have another mystery: the mystery of the mountain-climbing fish. Ask the students to imagine that they are with a group of geologists on an expedition to study the rock formations of the Himalayas. Ask: What continent would you travel in if you were studying the Himalayas? (Asia) Ask the students to imagine they are mountain climbing in Asia. Say: You are walking up a narrow mountain track on a cold, windy day. You must be very careful not to stumble over loose rocks because to the right is a cliff and a sheer drop of thousands of feet to the bottom. Suddenly, someone at the head of the group calls out, "Hey, look at this! We almost missed it." You look up and above your heads is a very interesting rock formation on the cliff face. Draw several parallel horizontal lines on the board and tell the students that the rock formation is in layers, like the stacked up layers of a cake. Say: As you study the rock more closely, you are shocked to discover, embedded in one of the rock layers, what appear to be seashells and the skeleton of a strange-looking fish. Draw some shells and a fish in one of the layers. You ask yourself, "How did animals from the sea get to the top of the tallest mountains in the world?" At first you are puzzled until you remember what you know about the rock cycle and how sedimentary rock is formed. Ask: Can you solve the mystery? How did sea animals get to the top of the Himalayas? Do fish climb mountains? If students have any difficulty solving the mystery, ask: Where is sedimentary rock formed? (on ocean floors) What can happen to ocean floors when two plates collide? (They can be pushed up into mountains.) Remind the students of the aluminum foil demonstration and how the colliding forces of the two plates pushed up mountains between them. Land that once was underwater can be lifted up in mountain building. The fish did not climb a mountain, but the sedimentary rock the fish was buried in was moved to another spot, thousands of feet higher. Remind the students that it takes millions of years for land to be pushed up into a mountain. Remind them that the Himalayas are still being pushed upward two inches a year.

Ask: Why didn't the fish's skeleton and the seashells decay? What preserved them for millions of years? (Accept all answers.) Tell the students that the fish skeleton and the seashells didn't decay because they had been turned into stone; they had been fossilized. Remind the students that when sedimentary rock is formed, layers of sediment stack up until the weight squeezes and cements the sediment together into rock. To describe how a fossil is formed, ask the students to imagine that a dinosaur died and its bones were washed into a warm inland sea. Mud immediately covered the bones, burying them before they could be eaten by other creatures. Over time, layer upon layer of sediment settled on top of the bones. Little by little, they began to absorb the minerals from the sediment around them. Each particle of bone was replaced with a particle of mineral until the bone became a fossil bone--a bone of stone.

Show the students pictures of fossils from Suggested Books or, if available, actual fossils. Tell the students that the dinosaur fossil you described is called a petrified fossil. Write petrified fossil on the board. Tell them that sometimes a dead animal is buried in sediment and then decays, leaving a hollow space exactly the same shape as its skeleton or shell in the mud. When the mud hardens into sedimentary rock, it preserves the mold of the bones or shell in all its detail. This kind of fossil is called a mold fossil. Write this on the board. If water carrying minerals eventually seeps into this stone mold fossil, it might take on the shape of the mold and form a copy of it called a cast fossil. Show the students a picture of fossil footprints from Suggested Books. Tell them that footprints in mud or other impressions can be fossilized, too. These are called trace fossils.

Point out to the students that the soft parts of animals and plants decay. It is usually the hard parts--bones, teeth, sticks, shell--that become fossilized. Show the students the assortment of seashells, nuts, leaves, bark and twigs. Select a shell and press it into a slab of clay. Show the students how the impression of the shell reveals clues to its shape and texture. Indicate the list of fossil types on the board and ask: What kind of fossil would this be? (mold fossil) Ask: If this mold fossil were filled with sediment that hardened into stone, what would that fossil be called? (a cast fossil) Tell the students they will be making a model fossil of whatever plant or animal material they choose. Divide the class into groups of five and distribute materials for making fossils. Have the students line the bottom of the container with Playdoh or clay. Press the object into the clay to make a mold of the object. Pour plaster of Paris into the mold and allow time to harden. In the spirit of the imaginary trip to the Himalayas, make a display of the cast fossils and have the students write descriptions of the trip and how they came upon the fossils.
 

Possible Homework

Have the students complete the fossil formation worksheet.

Tell the students that there is a substance called amber that is often used in jewelry. Ask them to find out what amber is and any other interesting facts about it.