1.2 The Rock Cycle

Question 1

What is meant by the term diagenesis?

Answer 1

Diagenesis includes all processes that occur in sediments at low temperatures and pressure at or near the Earth’s surface.

Question 2

What is meant by the term metamorphism?

Answer 2

The changing of rocks in the Earth’s crust by heat and/or pressure and/or volatile content.

Metamorphism is isochemical (the chemical composition does not change) and occurs in the solid state.

Question 3

What are igneous rocks?

Answer 3

rocks that have crystallised from magma

Question 4

What is partial melting?

Answer 4

when only a portion of rock in the lower crust or upper mantle is melted

Question 5

What is recrystallisation?

Answer 5

the solid state process that changes minerals into new crystalline metamorphic minerals

Question 6

What is crystallisation?

Answer 6

Crystallisation occurs during the cooling of magma or lava so that solid mineral crystals form.

Question 7

What is meant by burial as a process within the rock cycle?

Answer 7

the covering of sediment by younger layers of sediment

Question 8

What is a sedimentary rock?

Answer 8

A rock composed of fragments that have been deposited, compacted and cemented.

Question 9

What is a clast?

Answer 9

a fragment of broken rock produced by mechanical weathering and erosion

Question 10

What is magma accumulation?

Answer 10

magma collecting within a magma chamber

Question 11

What is an intrusion?

Answer 11

Igneous rock that has formed below the Earth’s surface, where magma is forced into pre-existing rocks.

Question 12

What is extrusion?

Answer 12

The emission of magma onto the Earth’s surface where it forms a lava flow.

Question 13

What is foliation?

Answer 13

Foliation is a texture in metamorphic rocks formed by the preferred alignment of flat/tabular minerals.

Question 14

What is deposition?

Answer 14

the laying down of sediment that occurs when a transporting agent loses energy

Question 15

What is weathering?

Answer 15

the breakdown of rocks in situ

Question 16

What is erosion?

Answer 16

the removal of weathered material, usually by the physical action of transported fragments

Question 17

What is transport?

Answer 17

the means by which weathered material is moved from one place to another by water, wind, ice or gravity

Question 18

What is uplift?

Answer 18

the return of buried rocks to the Earth’s surface by tectonic forces

Question 19

Describe the boundary between the diagenesis of sediments and metamorphism.

Answer 19

The boundary is gradational - a sedimentary shale grades into a metamorphic slate; the change is gradual and a rock can exist at stages along a spectrum from true shale to true slate.

Question 20

What occurs at the boundary between igneous and metamorphic rocks?

Answer 20

partial melting

Question 21

Which rocks form at low pressures and low temperatures?

Answer 21

sedimentary rocks

Question 22

Which rocks form at high pressure?

Answer 22

metamorphic rocks

Question 23

Which rocks form at very high temperatures or high temperature and greater than 200 MPa?

Answer 23

igneous rocks

Question 24

What is the main observable difference between an igneous rock formed at greater depth and one formed close to or at the surface?

Answer 24

igneous rocks formed at greater depth have larger crystals

Question 25

Which group of rocks will not contain calcite: igneous, metamorphic or sedimentary?

Answer 25

igneous

Question 26

Which mineral is indicative of metamorphism: mica, augite or garnet?

Answer 26

garnet

Question 27

Which common igneous mineral is not found in sedimentary or metamorphic rocks: K-feldspar, olivine or augite?

Answer 27

olivine

Question 28

If a rock is observed to have beds (layers), is it igneous, sedimentary or metamorphic?

Answer 28

sedimentary

Question 29

If a rock is observed to have foliation (alignment of minerals), is it likely to be igneous, sedimentary or metamorphic?

Answer 29

metamorphic