Every Rock Tells A Story

This entry is an activity for a professional development course.

Session 2 - Every Rock Tells a Story
The following materials and information will be needed to introduce students to sedimentary rocks and fossils. This activity will help students to understand the information they can obtain from observing fossils and layered rocks.
Learning goals: Describe the stories that fossils and layered rocks tell.
Purpose - To have students understand how limestone is formed.
To have students understand how sandstone and shale are formed.
To have students observe fossils and understand how fossil imprints are made.
National Science Education Standard
Fossils provide important evidence of how life and environmental conditions have changed.
Materials needed:
A sample of limestone
Vinegar
Sandstone
Shale
Jars
Sand
Clay or mud
Magnifying lenses
Water
Journals
Samples of fossils or pictures of fossils
Clay
Small shells
Leaves, flowers or twigs



Introduction
Explain to students that limestone is a main component of cement. It also produces lime when it is burned and lime is one of the major components of glass and mortar. The students will learn that not all sedimentary rocks are made of particles of eroded rock. Limestone is made of bits of shell fragments of millions of tiny sea animals. Layers of powdered skeletons and shell fragments settle on the bottom of the sea. The weight of the first layers press the shell fragments into solid rocks.
Experiment - The students will test a sample of limestone to see if it is made of calcite. They will place of few drops of vinegar to the limestone. Does it bubble of fizz ? If the answer is yes limestone is present.
Conclusion - Tell the students that shellfish take calcite from the sea water and use it to build their shells and coral polyps use calcite to build coral reefs. Since limestone is built from bits of shells and corals, it is almost entirely calcite.

Activity # 2

Explain to students how sedimentary rocks are formed. As you discuss the way that sediments of eroded rock are carried by water and deposited at the bottom of the sea or in river beds, show students the jar with layers of sand and clay. The students will need to imagine layers and layers of sediments accumulating under the ocean for millions of years until the weight of the top layers presses the lower layers into hard sedimentary rocks.
Observation - Recording of Data -Ask students to identify the layers in the jar. They will write their observations in a journal . They will also illustrate and label the layers of sediment. The students should identify layers of sand and clay in the jar. Then show the students sandstone and shale and ask them to identify them. The students will examine the shale and sandstone with a magnifying glass.
Note: For this activity the teacher will place layers of sand, clay or mud in a jar. Alternate layers until the jar is two- thirds full. Add water to the jar, let the water settle for a day or two.
Activity # 3
Let students observe samples of fossils or pictures of fossils. Students will determine if the fossil is the remains of an animal or plant . Also, they will determine if the fossil is an imprint or an impression ? Discuss with students that fossils were formed thousands and millions of years ago.
The students will make imprints in the clay by gently pressing the objects provided into the flattened clay. The students will then write in their journals what would happen if the imprints were left left in soft clay or mud at the bottom of the lake. What would have to happen to make a fossil.
Vocabulary: sedimentary rocks, metamorphic rocks, igneous rocks, shale, sandstone, imprints, fossils, layered rocks, erosion, limestone, calcite, coral