Mystery File© Learning A–Z All rights reserved. www.sciencea-z.com

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min

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ls, r

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ks, a

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England

FrancE

The White cliffs are along the coast of dover, England.

dover

Credits: left: © Jérôme Berquez/Dreamstime.com; right: © iStockphoto.com/fotofermer

imagine you’re on a boat headed from France to england. You see something huge ahead.

it looks like a white wall rising from the water. Welcome to the White cliffs of dover!

The White cliffs are made of a type of chalk found in nature. most of the chalk looks white because it’s made of a white mineral called calcite. But the bottom layer of chalk also has clay mixed in. The clay makes some of the chalk look gray.

ocean waves pound against the White cliffs. over time, the waves, wind, and rain remove thin layers of chalk. This process, called erosion, is gradually changing the coastline of dover, a town in england. in fact, the cliffs lose about 1 centimeter (0.38 in.) of chalk every year due to erosion. so take a good look at the White cliffs because they won’t last forever!

Is chalk a rock?

Mystery File Question

Cliffs of Chalk

You may have drawn with chalk. But you’ve probably used it in other ways, too, without realizing it. chalk is used to make toothpaste, stomach medicine, and cleaning powders.

Science In Your World

chalk

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Credits: © David Spears (Last Refuge)/ardea.com© Learning A–Z All rights reserved. www.sciencea-z.com

Minerals, Rocks, and Soil } Rocks } Mystery File Chalk

all natural chalk starts with tiny living things called algae (al-gee). some algae grow shells made of calcite. When the algae die, their shells sink to the bottom of the ocean. The shells build up in layers. The weight of the water pushes on the shells. They get stuck together. eventually, the layers form a solid, nonliving material—chalk!

Thanks, algae!

algae live in the ocean. Some have hard shells of calcite.

HoW cHalk FormS

1. When algae die, their shells sink to the bottom of the ocean.

algae

shells chalk layers

chalk cliff

ocean surface

2. The shells of algae build up in layers. The layers get buried, pressed, and glued, forming chalk.

3. Forces inside Earth push the chalk up, exposing it at the surface.

Mystery File Response Sheet

Key Question: What are the properties of rocks?

List the details you found in every I.File that your team read. Use the I.Team Evidence section of your I.File Response Sheet.

________________________________________________________________ T F ?

________________________________________________________________ T F ?

________________________________________________________________ T F ?

________________________________________________________________ T F ?

________________________________________________________________ T F ?

________________________________________________________________ T F ?

Now decide whether each of the details you listed is also true for the Mystery File. Circle one answer for each detail: T = true F = false ? = not sure

did you circle T (true) for all the details? Yes No

Mystery File Question: Is chalk a rock? Yes No

Use evidence to answer the Mystery File Question. Write in complete sentences.

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