Thames & Kosmos Kids First: Crystals, Rocks & Minerals handleiding

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The rock cycle

The various rock categories are transformed over

the course of cycles lasting millions of years.

Igneous rocks such as basalt, granite, and pumice

are exposed to the elements and turn to

sedimentary rocks. Others change into

metamorphic rocks.

When continents start to drift toward each

other, they often compress the ocean deposits

lying between them and push them upward into

folded mountain ranges — which is how the Alps,

the Himalaya, and many other well-known

mountain ranges formed. Of course, in time they

will wear down and

form new sedimentary

rocks.

Then, some

deposits get back into

Earth’s depths again,

are melted, and form

new igneous rocks. This

completes the cycle.

ABOUT

LIMESTONE

The dark brown limestone in your kit formed

millions of years ago from seawater. The lime

in it, which is actually white, was colored

dark by clay impurities. Its basic component,

though, is tiny crystals of calcite. Try testing

whether the limestone dissolves in acid.

SEDIMENTARY ROCK: WEATHERED AND DEPOSITED

Not even mountains last forever. Rain, frost, and wind attack the rock

and carry it off piece by piece. Rivers and streams wash chunks away

and wear them down to gravel, sand, and mud. In places where the

water flows more slowly, these materials settle as deposits, or

sediment — particularly at the mouths of rivers and in the ocean.

In time, many different layers will accumulate, and the pressure and

heat will press them together into solid rock called sedimentary rock.

These can also be materials that have formed out of and been

deposited by ocean water, such as limestone and salt — and the

limestone and diatomaceous shells of billions of tiny sea animals.

Hardness Density

2-4 2.8

CHECK IT OUT

Test yourself! Can you put

your rock samples in the

correct spots on the

diagram?

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