Geology: Classification of Rocks

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Questions and Answers

What are igneous rocks?

Rocks that form from melted rock (correct)

Rocks formed from the remains of living organisms

Rocks that have changed due to heat and pressure

Rocks that form in layers

What is a metamorphic rock?

Rocks that have changed as a result of heat and pressure

What are sedimentary rocks?

Rocks that form when layers of sediment settle on top of one another and harden.

Earth's crust is made of example of and

rocks, boulders, and sand Signup and view all the answers

Rocks can be classified by how they are ________

formed Signup and view all the answers

List the three main types of rocks.

Igneous, sedimentary, metamorphic rocks Signup and view all the answers

What is magma?

Melted or molten rock below Earth's surface Signup and view all the answers

Rocks formed from molten rock are called _____ rocks.

igneous Signup and view all the answers

The term 'igneous' comes from the Latin word meaning _____.

fire Signup and view all the answers

When magma reaches Earth's surface as ___, it cools quickly and hardens into solid igneous rock in just a few _ to ___.

lava, minutes, days Signup and view all the answers

Pumice is formed by air quickly cooling lava, which traps gas bubbles in this type of rock.

true Signup and view all the answers

What happens when magma cools slowly?

The slower the cooling process, the larger the crystals will be. Signup and view all the answers

Why would you need a microscope to see an igneous rock's crystals?

It indicates that the lava cooled quickly. Signup and view all the answers

_____ rock forms when layers of sediment settle on top of one another and harden.

Sedimentary Signup and view all the answers

What makes up sediment?

Rocks, soil, shells, dead animal matter, and dead plant matter Signup and view all the answers

How are sedimentary rocks classified?

By the minerals found in the sediment. Signup and view all the answers

Examples of sedimentary rocks include:

Limestone, sandstone, shale, and mudstone Signup and view all the answers

Metamorphic rocks can change form completely due to and .

heat, pressure Signup and view all the answers

What may heat and pressure cause to change?

Mineral crystals Signup and view all the answers

Chemical changes in the rock may form ________ types of minerals.

new Signup and view all the answers

Graphite is made entirely of _____.

carbon Signup and view all the answers

What can graphite be turned into?

Diamond Signup and view all the answers

What is a much harder mineral on the Mohs scale?

Diamond Signup and view all the answers

Some minerals have ________, meaning they may break along a smooth flat surface.

cleavage Signup and view all the answers

Hardness is how easily a mineral can be _____.

scratched Signup and view all the answers

Each mineral has crystals that are a particular shape called _____.

crystal shape Signup and view all the answers

What is the term for the color left by a mineral scratched on a special plate?

streak Signup and view all the answers

What is luster in terms of minerals?

It is the way the surface of the mineral reflects light. Signup and view all the answers

The same mineral can be different in terms of _____?

color Signup and view all the answers

What are minerals?

Natural non-living solid crystals that make up rocks Signup and view all the answers

Study Notes

Classification of Rocks

Igneous Rocks: Formed from melted rock; can be classified as either intrusive or extrusive based on cooling location and speed.
Metamorphic Rocks: Created under heat and pressure, resulting in physical and chemical changes in existing rocks.
Sedimentary Rocks: Developed through layers of sediment compacting and cementing over time.

Types of Rocks

Three Main Kinds: Igneous, sedimentary, and metamorphic represent the primary classifications of rocks.
Examples of Igneous Rocks: Include granite, obsidian, gabbro, and pegmatite, with characteristic properties based on cooling processes.
Examples of Sedimentary Rocks: Comprise limestone, sandstone, shale, and mudstone.

Formation Processes

Magma: Refers to molten rock found beneath the Earth's surface; when it surfaces as lava, it cools quickly.
Cooling of Lava: Rapid cooling leads to smaller crystals; slower cooling allows larger crystals to form.
Sediment Composition: Includes rocks, soil, shells, and organic matter, which accumulate and result in sediment formation.

Metamorphism

Metamorphic Processes: Involves the transformation of existing rocks due to heat, pressure, and chemical changes.
Crystal Changes: Heat and pressure can alter mineral crystals, forming new mineral types.

Mineral Characteristics

Cleavage: Some minerals may split along smooth surfaces; not all possess this property.
Hardness: Describes how easily a mineral can be scratched; measured using the Mohs scale.
Crystal Shape: Each mineral features a unique crystal structure.
Streak: The color left behind when a mineral is scratched on a plate.
Luster: Refers to the way a mineral's surface reflects light, affecting its appearance.

Unique Properties

Graphite: Composed entirely of carbon; subjected to heat and pressure can transform into diamond, a much harder mineral.
Color Variability: The same mineral may appear in different colors due to impurities or other factors, affecting identification.

Summary of Rock Lifecycle

Weathering and Erosion: Processes that move sediment locations, with deposition occurring layer by layer over time, held together by weight and chemical processes.

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Description

Test your knowledge on the three main types of rocks: igneous, metamorphic, and sedimentary. Explore their formation processes and characteristics along with examples of each type. This quiz will help reinforce your understanding of geology basics.