C4.3 (igneous rocks)

Question 1

What are igneous rocks/ how are igneous rocks formed?

Answer 1

Igneous rocks are rocks made when liquid rock (lava and magma) cools and freezes.

Question 2

Give some properties of igneous rocks.

Answer 2

• Igneous rocks are hard and durable. You cannot easily crush or scratch them.
• Igneous rocks consists of interlocking crystals- this explains why they are not porous.
• Igneous rocks do not react with acids.
• Igneous rocks do not contain fossils.

Question 3

What are intrusive igneous rocks?

Answer 3

Intrusive igneous rocks form from magma that cooled slowly, deep underground. The crystals that consist of intrusive igneous rocks are large.

Question 4

What are extrusive igneous rocks?

Answer 4

Extrusive igneous rocks form lava that cooled quickly. The crystals that consist of extrusive igneous rocks are small.

Question 5

Give some examples of both intrusive and extrusive igneous rock.

Answer 5

Intrusive - granite

Extrusive - obsidian and basalt

Question 6

What is magma?

Answer 6

Magma is liquid rock below the Earth’s surface.

Question 7

What is lava?

Answer 7

Lava is liquid rock above the Earth’s surface.

Question 8

Why do igneous rocks not contain any fossils?

Answer 8

Igneous rocks do not contain any fossils. This is because any fossils in the original rock will have melted when the rock melted to form magma.