Rocks

Question 1

Name the three main types of rocks.

Answer 1

Igneous, sedimentary, and metamorphic.

Question 2

Why do people study rocks? What can it tell us?

Answer 2

By studying rocks’ properties, we can learn about their origins and uses. For instance, granite, a hard igneous rock, is commonly used in construction due to its durability and resistance to heat, chemicals, and liquid absorption.

Question 3

What is igneous rock?

Answer 3

A type of rock formed from lava on the surface or magma beneath the ground

Question 4

Describe the two types of igneous rock?

Answer 4

Intrusive: formed when magma cools and solidi¬fies slowly beneath the Earth’s surface. E.g. Granite.
Extrusive igneous rock: formed when lava from a volcanic eruption cools quickly on the Earth’s surface. E.g., Basalt, pumice.

Question 5

Explain how crystals form in igneous rocks.

Answer 5

When hot molten rock, called magma, cools down, it turns into solid rock. As it cools, tiny particles in the magma start arranging themselves in an organized way, forming what we call crystals. These crystals come in different sizes and shapes depending on how fast the magma cools and what minerals are in it. If the magma cools slowly, big crystals form. If it cools quickly, the crystals are smaller. The type of crystals that form also depends on what minerals are in the magma.

Question 6

What is the most common type of rock?

Answer 6

Igneous rock.

Question 7

How are intrusive and extrusive igneous rocks different.

Answer 7

Extrusive rocks that form on the Earth’s surface cool quickly. This means they usually have small mineral grains.
Intrusive rocks cool more slowly and have larger mineral grains.

Question 8

What is sedimentary rock? How is it formed?

Answer 8

Sedimentary rock: rock formed when layers of particles (sediments) are pressed together by the weight of the overlying rock, or when water evaporates to leave behind a solid substance.
Sedimentary rocks are sometimes formed from the remains of plants, animals and other living things. For example, shells and hard parts of sea organisms break down and are deposited in layers on the ocean floor.

Question 9

What are some examples of sedimentary rock?

Answer 9

Sandstone, conglomerate, coal, and shale.

Question 10

What is meant by the term ‘sediment’?

Answer 10

Particles of rock eroded from the landscape, and then transported and deposited by water and wind.

Question 11

What is a fossil?

Answer 11

The imprints of an animal, plant, bacteria or other living organism preserved in rock

Question 12

What are some examples of igneous rocks?

Answer 12

Basalt, granite, obsidian, and pumice.

Question 13

What is conglomerate rock?

Answer 13

Sedimentary rock made up of rounded pebbles of different sizes that have been cemented together

Question 14

What sort of texture do sedimentary rocks have?

Answer 14

Grainy textures that may be porous and may contain fossils.

Question 15

Explain the Law of Superposition and why it is helpful to scientists.

Answer 15

The Law of Superposition states that in any sequence of undisturbed sedimentary rock layers, the oldest rocks are at the bottom, and the youngest rocks are at the top. This means that over time, as sedimentary layers accumulate, each new layer is deposited on top of the previously formed layers. This principle is crucial for understanding the relative ages of rock layers and the sequence of events in Earth’s history. It helps geologists and archaeologists interpret the past by studying the layers of rocks and the fossils contained within them.

Question 16

How do people classify rocks?

Answer 16

The classification of rocks involves observing visible features and mineral composition to identify their type.

Question 17

What is transparency (related to rocks)?

Answer 17

Transparency is how much light can pass through a rock.

Question 18

What does composition mean (related to rocks)?

Answer 18

Composition means what the rock is made of, including the structure and size of the grains.

Question 19

What does cleavage mean (related to rocks)?

Answer 19

Cleavage is how rocks break along smooth lines when hit.

Question 20

Why do people study rocks?

Answer 20

Studying rocks helps scientists learn about Earth’s history and processes.

Question 21

What does translucent mean?

Answer 21

Allowing light to pass through, but not transparent; semi-transparent.

Question 22

What is metamorphic rock, and how does it form?

Answer 22

Metamorphic rock is a type of rock formed when igneous, sedimentary or older metamorphic rocks are heated or squeezed. It forms when existing rocks—igneous, sedimentary, or older metamorphic—undergo intense heat and pressure within the Earth’s depths. This transformation occurs over millions of years.

Question 23

What is contact metamorphism?

Answer 23

Contact metamorphism is a type of metamorphism where rock minerals and texture are changed, mainly by heat, due to contact with magma.

Question 24

What is regional metamorphism?

Answer 24

Regional metamorphism is a type of metamorphism where rock minerals and texture are changed by heat and pressure over a wide area or region.

Question 25

Describe the main properties of metamorphic rocks.

Answer 25

Metamorphic rocks have visible crystals.
They barely have pores or openings.
They have alternate bands of dark and light minerals.
They react with acid.

Question 26

List some examples of metamorphic rock.

Answer 26

Marble, slate, and quartzite.

Question 27

What are clastic sedimentary rocks?

Answer 27

A type of sedimentary rock formed from the accumulation and lithification of mineral and rock fragments, typically transported and deposited by water, wind, or ice.

Question 28

What are bioclastic sedimentary rocks?

Answer 28

A sedimentary rock primarily composed of organic remains such as shells, skeletons, and other biological debris, often formed in marine environments where organisms contribute to the sedimentary material.

Question 29

What are chemical sedimentary rocks?

Answer 29

A sedimentary rock that forms through the precipitation of minerals from a solution, often in bodies of water such as lakes or oceans, without the involvement of organic material.

Question 30

Explain the rock cycle.

Answer 30

The rock cycle is a model that describes the formation, breakdown, and reformation of a rock as a result of sedimentary, igneous, and metamorphic processes.

Question 31

What is an index fossil?

Answer 31

A fossil of something that existed for a short time, but was widespread.

Question 32

What is meant by the term ‘weathering’?

Answer 32

Weathering is the chemical and physical processes that change the characteristics of rocks on the Earth’s surface. Weathering results in the formation of sediments.

Question 33

Explain physical weathering.

Answer 33

Physical weathering is caused by physical changes such as changes in temperature, freezing/ thawing, and the effects of wind, rain, and waves.

Question 34

What is chemical weathering?

Answer 34

Chemical weathering is the weathering of rocks by chemical. E.g., acid rain, or the action of plant acids.

Question 35

What is erosion?

Answer 35

The movement of broken rock away from the site of weathering. Erosion moves the sediments to where they are deposited.

Question 36

What is biological weathering?

Answer 36

The breakdown of rocks by living things (biotic).

Question 37

What are ores?

Answer 37

Rocks containing minerals are known as ores.

Question 38

How was most iron ore formed? What is it used for?

Answer 38

Most iron ore was formed by sediments deposited on the sea floor. Iron ore is used to make steel.

Question 39

Explain how oil and natural gas were formed.

Answer 39

Oil and gas formed from microscopic animals and plants that lived in the oceans and lakes millions of years ago. When these animals and plants died, they sank to the sea floor and were covered by sediment. This sediment and the lack of oxygen changed the way they decayed. Heat from the Earth turned them into compounds high in carbon. The sediment slowly turned into sedimentary rock. The carbon compounds became oil and gas.

Question 40

Explain how coal was formed.

Answer 40

Coal was formed from plants that lived in swampy areas on land. They died and fell into swamps where they were covered by sediment. High pressure, heat, and a lack of oxygen changed and compressed the plant remains to form coal.