© oup: to be used solely in purchaser’s school or college 8g rocks and weathering rocks and...

© OUP: To be used solely in purchaser’s school or college

8G Rocks and weathering

Rocks and minerals

Erosion

Deposition



Rocks and minerals



8G Building the Earth


8G Rock band

Slate

The rocks we see all come from the thin, solid crust on the outside of the Earth.

They are all made of minerals.

A mineral is a chemical found in a rock.

Most minerals are mixtures of different chemicals.

Marble Granite


8G Weathering

Rock does not last forever. Look at the picture here – how can you tell that the rock has been damaged by the environment?

What might have done this damage?


8G Freeze-thaw


1. Water expands when it freezes.

2. Rocks contract during the day and expand at night.

3. Acid rain dissolves some rocks.

4. Soft rocks weather more quickly than harder rocks.

8G True or false?

Are these statements true or false?

TRUE

FALSE

TRUE

TRUE


1. Plants cannot cause rocks to crumble.

2. Granite gravestones weather more quickly than those made of limestone.

3. Rocks can be weathered by repeated heating and cooling.

4. Acid rain is made when oxygen dissolves in falling rain.

8G True or false?

Are these statements true or false?

FALSE

FALSE

TRUE

FALSE


Erosion



8G Break it, move it, shape it!

Rocks may last a long time but they do change.

Even the toughest rocks can be broken down to smaller particles. We call this process weathering.

Small particles may be moved around to new areas. We call this transportation.

The two processes together (weathering and transportation) are called erosion.


8G Move it! Fast!

What are the conditions that give the biggest rate of movement?

Where would you find these conditions?

Amount of water

Size of sediments

Speed of water flow

small small slow

medium medium medium

large large fast


8G Move it! Fast!

What are the conditions that give the slowest rate of movement?

Where would you find these conditions?

Amount of water

Size of sediments

Speed of water flow

small small slow

medium medium medium

large large fast


Deposition



8G Settle down!

As the water carrying sediments slows down, the sediments fall out of suspension.

The sediments make a layer on the bottom of a lake or river.

New sediments are laid down on top, pressing the ones below together.

Over thousands of years the sediments become stuck together to make a soft rock – sedimentary rock.


8G Age of sediments

Which rock type is oldest? How can you tell?

The fossil in layer 4 is part of an ammonite from 180 million years ago. What does this tell you about the age of layer 3?


1. Sedimentary rocks take thousands of years to form.

2. Sedimentary rocks never form in layers.

3. Sedimentary rocks often contain crystals.

4. Salt crystals stick the grains in sedimentary rocks together.

8G Sedimentary facts

True or false?

TRUE

FALSE

FALSE

FALSE


1. The first process involved in making sedimentary rocks is called weathering.

2. Deposition lays down sediments.

3. It is unlikely that you would find a fossil in a sedimentary rock.

4. Chalk is a sedimentary rock.

8G Sedimentary facts

True or false?

TRUE

TRUE

FALSE

TRUE


8G Water on Mars?

This image shows the surface of Mars. It’s obvious that water flowed here once! Or is it? What do you think?


8G Craters on the Moon

Which of these craters is the oldest? How can you tell?


8G Why so sharp?

The features on the Moon’s surface are very sharp.

This is because there is no water to erode

away the edges.

This is because the low gravity stops rocks

from crumbling.Which is correct?Why?


1. The crust of the Earth is…

a) very thin compared with the layers underneath

b) very thick compared with the layers underneath

c) missing under the Pacific Ocean.

2. Sediments are…

a) the small fragments of rocks produced by weathering

b) the water currents in a fast flowing stream

c) always formed a long time ago.

8G Rock quiz


3. Weathering is…

a) the breakdown of rocks by the environment

b) the building up of rock by piling sediments up in layers

c) predicting the likelihood of rainfall in a particular area.

4. Acid rain dissolves limestone better than granitebecause…

a) limestone contains more calcium carbonate than granite

b) limestone is a softer rock than granite

c) granite is waterproof but limestone is not.

8G Rock quiz


5. Fossils are…

a) remains of dead plants or animals preserved in rock

b) made when granite is eroded

c) old teachers.

6. Which stream would carry the most sediments? Why?

a) a large river in flood

b) a small river flowing very quickly

c) a large river flowing slowly.

8G Rock quiz

© oup: to be used solely in purchaser’s school or college 8g rocks and weathering rocks and...

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