7.1 Earth Structure

Question 1

What is the structure of the Earth?

Answer 1

1. The outer layer of the Earth is the Crust with a depthy between 8 and 40km
2. Beneath the Crust you find the Mantle. The Mantle is mostly made of solid rock, but it can flow very slowly. Hotter rock rises and cooler rock sinks.
3. Beneath the Mantle is the Outer Core which is mainly made up of iron and nickel and is liquid.
4. In the centre of the Earth you find the Inner Core which is mainly made up of iron and nickel and is solid.

Question 2

What’s in the Crust?

Answer 2

The Earth’s crust is made up of many different types of rocks. Most rocks are mixtures of naturally-occurring elements or compounds called minerals.

Question 3

What are the three types of rocks?

Answer 3

1. Sedimentary Rocks
2. Igneous Rocks
3. Metamorphic Rocks

Question 4

Properties of Sedimentary Rocks

Answer 4

They are made up of separate grains that can be seen with a hand lens.
They are usually porous. Air or water can get into these cracks.
Most Sedimentary Rocks are soft and can be scratched easily.

Question 5

How are Sedimentary rocks made?

Answer 5

Sedimentary rocks are made up of pieces of older rocks. The process has several stages:
Weathering
Erosion and transport
Deposition
Compaction and Cementation

Question 6

What is weathering?

Answer 6

Weathering is where rocks are broken up into smaller pieces called sediments. The main types of weathering are:
Physical Weathering
Chemical Weathering
Biological Weathering

Question 7

What is erosion?

Answer 7

Erosion is the breaking of rocks into sediments and their moving away. Transport processes move sediments far from the original rock.

Question 8

What is deposition?

Answer 8

Deposition is where sediments stop moving and settle in one place.
Layers of different sediment may settle on top of each other causing layers called strata to form.

Question 9

What is compaction?

Answer 9

Compaction is where the weight of sediment above squashes the sediment below.

Question 10

What is cementation?

Answer 10

Where another substance sticks the sediment together.

Question 11

How do Igneous rocks form?

Answer 11

Igneous rocks form when liquid rock (magma) freezes. Almost all types of igneous rocks consist of crystals with no gaps between them. Each crystal is made up of particles of one mineral.

Question 12

Properties of Igneous rocks

Answer 12

Hard and Durable
This makes Igneous rocks useful for pavements and underneath railway tracks.

Question 13

Why are types of igneous rocks different?

Answer 13

Depending on the time magma takes to freeze, its particles have varying times to form crystals. Different crystal sizes form different types of igneous rocks.

Question 14

How are metamorphic rocks formed?

Answer 14

They are formed over millions of years when heat, high pressure or both rearrange the particles of an existing rock changing it to a new rock. They are not porous.

Question 15

How is marble formed?

Answer 15

Marble is formed when limestone below the Earth’s surface heats up.

Question 16

How is Slate formed?

Answer 16

Slate forms when the high pressure underground squashes the mudstone squeezing out the water and forming new layers of crystals.

Question 17

What is the rock cycle?

Answer 17

The rock cycle is an ongoing process that converts one type of rock into another.

Question 18

What is uplift?

Answer 18

Uplift is when forces inside the earth push rocks upwards.

Question 19

What is a ceramic?

Answer 19

A ceramic is a compound. They include metal silicates, oxides, carbides and nitrides.

Question 20

Properties of Ceramics

Answer 20

Hard
Brittle
Stiff
Solid at room temp. - very high melting point
Strong when forces press on them
Easy to break when stretched
Electrical insulators.
Do not react with water, acids or alkalis.