Igneous Rocks Overview

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Questions and Answers

What are igneous rocks defined as?

Rocks that dissolve in water

Rocks formed from sediment compaction

Rocks that are transformed from other rock types

Rocks formed from the cooling of magma and lava (correct)

Where does magma reside in relation to the Earth's surface?

On the Moon's surface

Above the Earth's surface

On the Earth's surface

Beneath the Earth's surface (correct)

Which statement accurately describes lava?

It is always found below the Earth's surface.

It is a solid form of rock.

It is the molten rock that has erupted onto the Earth's surface. (correct)

It forms only in oceanic regions.

How are intrusive igneous rocks formed?

By slow cooling of magma trapped beneath the surface Signup and view all the answers

What determines the size of crystals in igneous rocks?

The cooling rate of magma Signup and view all the answers

Which of the following is true about magma and lava?

Magma is liquid rock under the surface, and lava is rock that has cooled above ground. Signup and view all the answers

To form large crystals in intrusive igneous rocks, what is the cooling speed of magma?

Slowly Signup and view all the answers

What is the primary difference between magma and lava?

Magma is located beneath the surface; lava has erupted onto the surface. Signup and view all the answers

What effect can small amounts of other chemicals have on quartz?

They can change its color. Signup and view all the answers

Which statement best describes a geologist?

A scientist who studies rocks. Signup and view all the answers

What is a distinguishing feature of gneiss compared to sandstone?

Gneiss has layers of different colors. Signup and view all the answers

Which rock type is known to have layers of different sized grains?

Sandstone Signup and view all the answers

Which of the following can describe gas holes in rocks?

Holes can be large, small, or absent. Signup and view all the answers

What characteristic might a rock with large gas holes have?

It formed rapidly with gas release. Signup and view all the answers

Which of the following rock types is most likely to have no holes?

Gneiss Signup and view all the answers

Which property of rocks is affected by the process of gas release during formation?

Presence and size of holes Signup and view all the answers

What does hardness measure in minerals?

How easily a mineral can be scratched Signup and view all the answers

Which mineral is known to be softer than a fingernail?

Talc Signup and view all the answers

On Mohs’ Scale of Hardness, which mineral has a hardness of 8?

Topaz Signup and view all the answers

What is the outermost layer of the Earth's structure?

Crust Signup and view all the answers

Which mineral will definitely scratch talc?

Diamond Signup and view all the answers

What is the hardness of diamond on Mohs’ Scale?

10 Signup and view all the answers

Which characteristic is NOT used to describe the Earth's layers?

Color Signup and view all the answers

Which mineral is able to scratch quartz?

Feldspar Signup and view all the answers

What is a characteristic of minerals?

They are naturally occurring. Signup and view all the answers

Which of the following describes the term 'hardness' in relation to minerals?

The resistance of a mineral to being scratched. Signup and view all the answers

Which substance is NOT considered a mineral?

Cubic zirconia Signup and view all the answers

What property would a geologist specifically use to identify a mineral's color near its surface?

Streak Signup and view all the answers

Which of the following correctly defines 'rocks'?

They are made of one or more minerals. Signup and view all the answers

How do geologists determine the hardness of minerals?

By comparing them to a series of known minerals. Signup and view all the answers

Which feature of minerals relates to their ability to reflect light?

Lustre Signup and view all the answers

What does the Mohs’ hardness scale measure?

The scratch resistance of minerals. Signup and view all the answers

What is defined as the breaking down of rocks and minerals?

Weathering Signup and view all the answers

Which of the following is a cause of physical weathering?

Heating and cooling of rocks Signup and view all the answers

What type of weathering occurs due to physical forces from non-living things?

Physical Weathering Signup and view all the answers

How does moving water contribute to physical weathering?

By causing abrasion Signup and view all the answers

Which layer of a rock is most likely affected by the physical weathering process of heating and cooling?

Outer layer Signup and view all the answers

What is the primary difference between weathering and erosion?

Weathering breaks down rocks; erosion transports them. Signup and view all the answers

Which statement best describes physical weathering?

It requires a physical force to break down rocks. Signup and view all the answers

What is NOT a type of weathering?

Erosion Signup and view all the answers

Study Notes

Igneous Rocks

Igneous rocks form from magma and lava cooling and solidifying.
Magma is molten rock found beneath the Earth's surface.
Lava is molten rock found above the Earth's surface.

Intrusive Igneous Rocks

Intrusive igneous rocks form below the Earth's surface when magma is trapped in small pockets.
Magma cools slowly to form large crystals.

Layers

Some rocks have layers of different colors (e.g. gneiss).
Some rocks have layers of different sized grains (e.g. sandstone).

Air Holes

Some rocks contain holes from gases in the rocks when they were formed.
The holes can be large, small, or not present at all.

Rocks and Minerals

Minerals are naturally occurring substances with a specific chemical composition, structure, and properties.
Rocks are made up of one or more minerals.

Identifying Minerals

Geologists identify minerals based on properties like:
- Lustre: How light reflects off a mineral's surface.
- Streak: The color of a mineral's powder.
- Hardness: How easily a mineral can be scratched.

Hardness

Hardness is how easily a mineral can be scratched.
Talc is a soft mineral that can be scratched with a fingernail.
Diamond is a very hard mineral that cannot be scratched by other minerals.

Mohs’ Scale of Hardness

Friedrich Mohs developed a scale of hardness with ten common minerals.
Harder minerals can scratch softer minerals.

Earth's Structure

The Earth has four main layers, each with different properties.
Crust: The outermost layer, thin (5-70km) and made up of solid rock.
Mantle: Thickest layer (2900km) and made of mostly solid but with molten rock in the asthenosphere.
Outer Core: Liquid layer (2200km), made up mostly of iron and nickel.
Inner Core: Solid core (1220km), made up mostly of iron and nickel.

Weathering

Weathering is the breaking down of rocks and minerals.
There are three types of weathering: physical, chemical, and biological.

Physical Weathering

Physical weathering happens when a physical force breaks down a rock by non-living things.
Physical weathering can occur through:
- Heating and cooling of rocks causing outer layers to peel off.
- Abrasion from moving water in oceans or rivers.
- Ice wedging (water freezing and expanding in cracks).

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Description

This quiz explores the formation and characteristics of igneous rocks, including the differences between intrusive and extrusive types. It covers essential concepts like the composition of rocks and minerals, layering, and air holes formation. Test your understanding of these geological processes!