Rocks

Question 1

What are Rocks?

Answer 1

Solid materials occuring in the earth’s crust, composed of one or more minerals.

Question 2

(Set 1) Differences in rocks
- Mineral Content
- Hardness
- Origin

Answer 2

• Rocks are composed of one or more minerals, natural substances like quartz, calcite etc.
• Resistance to weathering + erosion
• Where and how they were created

Question 3

(Set 2) Differences in rocks
- Texture
- Density
- Shape

Answer 3

• How It feels to touch.
• Amount of rock compared to space it takes up.
• How they were laid down (strata or shapes)

Question 4

Rock cycle

Answer 4

• Magma cools to rock
• Magma melts rock during subduction
• Rock breaks down into sediments by the elements of weathering + erosion
• Reformation of rock through lithification.
• Changing of rocks structure by heat + erosion

Question 5

Igneous Rocks

Answer 5

Formed when magma rises from mantle and cools either intrusively or extrusively

Question 6

Basalt
Example, Characteristics, economic value

Answer 6

E.g Giant’s Causeway

Typically black to dark grey in colour, smooth hard rock

E. Value - Floor tiles, building veneer, road chippings etc.

Question 7

Basalt formation

Answer 7

Volcanic + extrusive rock,
DIVERGENT boundaries, approx 65m yrs ago, lava flowed through fissures, low silica content, Basic igneous rock

Question 8

Granite
Example, Characteristics, Economic Value

Answer 8

E.g Wicklow Mountains

Typically grey, has variations depending on proportions of various minerals like potassium and quartz. Course grained texture, hard + durable

E. Value - Construction of buildings, bridges, countertops, floor tiles etc.

Question 9

Granite formation

Answer 9

Plutonic rock, CONVERGENT boundaries approx 400m yrs ago, collision forming fold mountains, molten magma intruded with high silica content, cooled slowly, contains feldspar and quartz

Question 10

Deposition

Answer 10

Particles deposited as loosely packed sediments

Question 11

Cementation

Answer 11

Over time, natural minerals glue the particles together

Question 12

Compaction

Answer 12

The weight of water and overlying layers squeeze the sediments together.

Question 13

Sedimentary rocks

Answer 13

Formed from particles of animals, sea creatures, plant life and broken down rocks.
Sediments are laid down in layers or STRATA and separated by horizontal gaps in rock called bedding planes

Question 14

Organic sedimentary rocks

Answer 14

Formed from once living things or decayed vegetation

Question 15

Inorganic Sedimentary rocks

Answer 15

Formed from broken down sediments of other rocks.

Question 16

Limestone
Example,
Characteristics, economic value

Answer 16

E.g The Burren

Chalk like - pure limestone, white and easily eroded, - carboniferous limestone, over 50% calcium carbonate, grey in colour, more resistant

E. Value - Used in making of cement, glass and soil conditioner

Question 17

Limestone formation

Answer 17

Organic, 300m yrs ago, near equator, living things built up on sea floor, deposited sand mixed, calcium carbonate in living things, rock forms

Question 18

Sandstone example, Characteristics, economic value

Answer 18

E.g Caha mountains

Old red sandstone has colour due to presence of iron oxide, can be soft or hard depending on formation

E. Value: Sandstone is used as a decorative store in sculptures, headstones and pavment

Question 19

Sandstone formation

Answer 19

Inorganic, 380 million yrs ago, South of equator desert climate, weathering and erosion, transported by flash floods, sediments of fine sand deposited, compressed by weight Of seawater, calcium carbonate, iron and silica cemented rock

Question 20

Other sedimentary rocks

Answer 20

Coal - organic, Arigna, dead vegetation

Shale - inorganic, Slieve Elva - Burren, mud and clay. Quartz and calcite

Question 21

Metamorphic Rocks

Answer 21

Igneous or sedimentary rocks are subjected to great heat or pressure

Question 22

Metamorphic features

Answer 22

Smaller volume and minerals are transformed to high temperature minerals. Denser and more resistant to weathering or erosion.

Question 23

Regional metamorphism

Answer 23

(Dynamic) Friction at convergent boundaries creates heat and pressure, composition changes. E.g zone of subduction

Question 24

Contact Metamorphism

Answer 24

(Thermal): Rising molten magma changes composition of rocks in small area. E.g volcanic intrusion

Question 25

Marble
Example, characteristics, economic value

Answer 25

E.g Connemara

Coarse grained hard rock, smooth texture

E. Value - decorative stone, countertops, ornaments, sculptures

Question 26

Marble formation

Answer 26

Limestone or chalk changes due to Regional metamorphism, CONVERGANT plate boundaries, Calcite minerals recrystallised making denser rocks

Question 27

Quartzite
Example, characteristics, economic value

Answer 27

E.g Hill of Howth

Medium grained hard rock that exists in a variety of colours

E. Value - Countertops, surface roads

Question 28

Quartzite formation

Answer 28

Contact metamorphism, 400 million yrs ago, molten magma intruded in folding period and came in contact with sandstone, chemically changed to quartzite, extreme heat and pressure

Question 29

Active Margin
Example, what is formed here, features

Answer 29

E.g West coast of North America

Forms Igneous and metamorphic rock

Earthquakes, folding and volcanic belts

Question 30

Passive Margin
What is found here, features

Answer 30

Sedimentary rocks

Interior of plate pulls away, form when deposits of sediments or vegetation are compressed and cemented

Question 31

Human interaction with the rock cycle

Answer 31

1. Oil and gas exploration
2. Shaft Mining
3. Quarrying
4. Geothermal energy, use case study from volcanic activity chapter.