Rocks

Rocks

Middle School

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Learning Objectives

• Develop a model to describe the cycling of Earth's materials and energy flow.

• Explain how the sun and Earth's interior drive Earth's processes.

• Describe how melting, crystallization, and weathering form and change rocks.

• Characterize rocks based on their mineral composition, color, and texture.

Key Vocabulary

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Igneous Rock

Igneous rock is formed when hot, molten magma or lava from a volcano cools down and solidifies.

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Sedimentary Rock

Sedimentary rock is created from layers of sediment that are compacted and cemented together over a long period.

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Metamorphic Rock

Metamorphic rock is a type of rock that has been completely changed by extreme heat and intense pressure.

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Rock Cycle

The rock cycle is a continuous process that describes how rocks change from one type to another over time.

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Crystallization

Crystallization is the natural process where atoms neatly arrange themselves to form a solid with a crystal structure.

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Weathering

Weathering is the natural process that breaks down rocks and other materials on the Earth's surface into smaller pieces.

Key Vocabulary

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Sedimentation

Sedimentation is the process where sediments, soil, and rocks are added to a landform or landmass.

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Deformation

Deformation refers to the process by which rocks change their shape under the influence of stress.

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Melting

Melting is the process where solid rock transforms into a liquid state known as magma.

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Extrusive Rock

Extrusive rock is a type of igneous rock that forms from lava cooling quickly on Earth's surface.

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Intrusive Rock

Intrusive rock is an igneous rock formed from magma that cools slowly beneath the Earth's surface.

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Matter Cycling

Matter cycling describes the movement and exchange of matter through different parts of an ecosystem or system.

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Energy and Matter in Earth's Systems

• Energy flow and matter cycling drive all of Earth's processes.

• This causes both chemical and physical changes in Earth’s materials.

• The sun’s energy drives processes like weather on Earth’s surface.

• Energy from Earth's hot interior drives processes deep inside the planet.

Multiple Choice

What are the two fundamental drivers of all processes on Earth, such as the formation of rocks?

• Energy flowing and matter cycling

• The sun's heat and ocean currents

• Volcanic eruptions and earthquakes

• Wind patterns and water erosion

Multiple Choice

What is the relationship between the flow of energy and the cycling of matter on Earth?

• They cause physical and chemical changes in Earth's materials.

• They only affect the movement of water in the oceans.

• They are responsible for creating Earth's atmosphere.

• They only cause changes in living organisms.

Multiple Choice

Based on the sources of energy that drive Earth's systems, what would be the most likely consequence if Earth's interior cooled down significantly?

• Processes that rely on internal heat, like some rock formation, would be greatly reduced.

• All of Earth's processes would stop completely.

• There would be no change to Earth's processes.

• Only processes on the Earth's surface would be affected.

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Describing Rocks

Mineral Composition

• ​Rocks contain one or several different types of rock-forming minerals.

• ​​A rock's color often provides important clues about its mineral composition.

• ​For example, light-colored granite indicates a high content of silica.

Texture

• ​Texture is determined by the size, shape, and pattern of a rock's grains.

• ​​Coarse-grained rocks have large, easily visible mineral grains, giving them a rough feel.

• ​Fine-grained rocks have tiny grains only visible with a microscope, making them smooth.

Multiple Choice

What are the two primary characteristics used to describe rocks?

• Its mineral composition and its texture

• Its color and its weight

• Its age and its location

• Its hardness and its shape

Multiple Choice

What is the relationship between the size of a rock's mineral grains and its texture?

• Large, visible grains give the rock a coarse and rough texture.

• Small, microscopic grains give the rock a coarse and rough texture.

• The color of the grains determines the smoothness of the texture.

• The shape of the grains determines the color of the rock.

Multiple Choice

A geologist discovers a rock that is light in color and has large, easily visible mineral grains. What is the most logical conclusion about this rock?

• It likely has a high silica content and a coarse-grained texture.

• It must have a low silica content and a fine-grained texture.

• It is fine-grained because it is light-colored.

• It has a high silica content because its grains are large.

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Igneous Rocks: Formed from Fire

• Igneous rock forms when molten magma or lava cools and crystallizes.

• Extrusive rock forms from lava that cools quickly on Earth's surface.

• This rapid cooling results in a fine-grained texture, like in basalt.

• Intrusive rock forms from magma that cools slowly, creating coarse-grained granite.

Multiple Choice

What process is responsible for the formation of all igneous rocks?

• From the cooling and hardening of magma or lava

• From the layering and cementing of sediments

• From the intense heat and pressure on existing rocks

• From the weathering and erosion of mountains

Multiple Choice

What is the primary factor that determines whether an igneous rock has a fine-grained or coarse-grained texture?

• The types of minerals present in the molten rock

• The rate at which the molten rock cools

• The age of the molten rock

• The location of the rock on a continent

Multiple Choice

A geologist finds an igneous rock with very large, easily visible mineral crystals. What is the most logical conclusion about how this rock formed?

• It formed from lava that cooled very quickly on the Earth's surface.

• It formed from magma that cooled slowly below the Earth's surface.

• It is a type of basalt with very small mineral crystals.

• It was created during a fast-moving volcanic eruption.

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The Formation of Sedimentary Rocks

• Sedimentary rock forms from sediment, which are small pieces of rock or organisms.

• Weathering and erosion by wind and water break existing rocks into sediment.

• Sediment is transported by wind and water, then deposited in layers.

• Layers are compacted and cemented over time, forming solid rock.

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Multiple Choice

What are sedimentary rocks primarily formed from?

• Molten lava that has cooled very quickly

• Small pieces of rock or organisms

• Minerals that crystallize from magma underground

• Rock that has been changed by extreme heat and pressure

Multiple Choice

Which statement best describes the relationship between weathering, erosion, and deposition?

• Layers of rock are cemented together and then compacted by pressure.

• Weathering and erosion break down rock, which is then transported and deposited in layers.

• Sediment is heated until it melts and then cools to form a solid rock.

• Wind and water transport large rocks to a new location, where they become cemented.

Multiple Choice

A geologist discovers a large rock formation with distinct layers of sand and pebbles. What is the most logical conclusion about how this rock was formed?

• The rock was formed from the rapid cooling of molten lava.

• The rock was formed from layers of sediment being compacted and cemented.

• The rock was subjected to intense heat and pressure deep within the Earth.

• The rock was created by the chemical reaction of water and minerals.

Metamorphic Rocks: Changed by Heat and Pressure

• Metamorphic rock is existing rock changed by intense heat and pressure.

• This transformation process happens deep within the Earth's crust.

• Pressure can rearrange minerals into parallel layers, a feature called foliation.

Multiple Choice

How does a metamorphic rock form?

• By being changed by intense heat and pressure

• By cooling and hardening from lava

• By being weathered and eroded by wind

• By cementing together pieces of sediment

Multiple Choice

What effect does pressure have on the minerals within a metamorphic rock?

• It causes minerals to line up in parallel layers.

• It melts the rock into liquid magma.

• It breaks the rock into smaller sediments.

• It makes the rock cool down very quickly.

Multiple Choice

If a rock is subjected to intense pressure deep within the Earth's crust, what would you predict is the most likely outcome?

• A metamorphic rock with foliation

• A sedimentary rock with fossils

• An igneous rock with large crystals

• A volcanic rock with air bubbles

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The Rock Cycle: A Model of Matter Cycling

• The rock cycle models how matter cycles through physical and chemical changes.

• Igneous rock can weather into sediment, later forming sedimentary rock.

• Heat and pressure can transform rocks into metamorphic rock underground.

• Melted metamorphic rock cools to form new igneous rock, completing the cycle.

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Multiple Choice

What does the rock cycle model demonstrate?

• To show how matter cycles through physical and chemical changes

• To classify rocks based only on their color and size

• To explain how volcanoes erupt

• To locate the oldest rocks on Earth

Multiple Choice

What is the relationship between an igneous rock and the formation of a sedimentary rock?

• It must be weathered into sediment and then compacted.

• It must be melted into magma and then cooled.

• It must be subjected to intense heat and pressure.

• It must be immediately buried deep underground.

Multiple Choice

If a sedimentary rock is buried deep within the Earth, what is the most likely sequence of events for it to become a new igneous rock?

• The rock would be transformed by heat and pressure, then melt, and finally cool.

• The rock would be weathered into sediment, then compacted, and then cemented.

• The rock would cool, then be weathered into sediment, and then melt.

• The rock would melt, then be weathered into sediment, and then be compacted.

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Energy from Earth's Interior

• The rock cycle gets its energy from the immense heat inside Earth.

• This powerful heat melts rock into magma deep beneath the surface.

• It also provides the energy to create new metamorphic rocks underground.

• This internal energy pushes rock from deep inside up to the surface.

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Multiple Choice

What provides the energy for the rock cycle?

• The heat from deep inside the Earth

• The light and energy from the Sun

• The force of wind and water erosion

• The movement of glaciers over the land

Multiple Choice

How does the powerful heat inside Earth cause changes to rock?

• It causes rocks to become smaller and lighter.

• It breaks rocks down into soil and sand.

• It melts rock and forms new metamorphic rocks.

• It cools the surface of the Earth.

Multiple Choice

What is a logical outcome of the movement caused by Earth's internal energy?

• The surface of the Earth remains unchanged.

• Rock from deep within Earth is brought to the surface.

• All rocks on the surface melt into magma.

• The amount of rock on Earth decreases over time.

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Driving Force: Energy from the Sun

• Energy from the sun drives the formation of sedimentary rock on Earth's surface.

• The sun's energy powers weather, including the movement of wind and water.

• This energy causes weathering, erosion, and the deposition of sediment.

Multiple Choice

What is the primary driving force behind the formation of sedimentary rock on Earth's surface?

• Energy from the sun

• Heat from Earth's core

• Energy from volcanic eruptions

• Gravitational pull from the moon

Multiple Choice

How does solar energy lead to the weathering and erosion of rocks?

• By directly melting the surface of rocks.

• By causing chemical changes deep inside the Earth.

• By powering the movement of wind and water, which breaks down and moves rock.

• By creating intense pressure that forms new minerals.

Multiple Choice

If a planet nearly identical to Earth had a sun that produced much less energy, what would be the most likely long-term effect on its rock cycle?

• An increase in the rate of erosion and sediment deposition in other areas.

• The rocks would get harder and more resistant to breaking down.

• The formation of new volcanoes on the mountain.

• A decrease in the amount of wind and water on the mountain.

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Time and Scale in the Rock Cycle

• The rock cycle shows Earth is both stable and constantly changing.

• ​These changes happen over millions of years, a scale called geologic time.

• To us, large landforms like mountains can appear stable and unchanging.

• But they are always being slowly altered by the rock cycle.

Multiple Choice

What does the rock cycle reveal about the nature of Earth?

• It is a planet that is both stable and constantly changing.

• It is a planet that only experiences rapid, sudden changes.

• It is a planet that has stopped changing and is now static.

• It is a planet that is completely unstable and chaotic.

Multiple Choice

Why might a large mountain range appear to be unchanging to an observer?

• The changes are too slow to be noticed in a human lifetime.

• Mountains are not actually part of the rock cycle.

• The rock cycle only happens in oceans and volcanoes.

• Human activity prevents the mountains from changing.

Multiple Choice

Based on the principles of the rock cycle, what can be concluded about a mountain that is millions of years old?

• The mountain has been continuously shaped by the rock cycle.

• The mountain looks exactly the same as it did when it first formed.

• The mountain has likely finished changing and is now permanent.

• The mountain was formed by a process other than the rock cycle.

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Common Misconceptions

Misconception	Correction
Rocks are permanent and do not change.	Rocks are in a constant state of change through the rock cycle.
Metamorphic rocks are simply rocks that have melted.	Metamorphic rocks are altered by heat and pressure, but do not melt completely.
The rock cycle happens quickly, like the water cycle.	The rock cycle occurs over millions of years, a much longer lifespan.

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Summary

• Earth's processes are driven by energy flow and matter cycling.

• The sun's energy forms sedimentary rocks; Earth's interior energy forms other rock types.

• The rock cycle is a model showing how any rock can become a new rock.

• Rocks are classified by composition and texture; geologic change is extremely slow.

Poll

On a scale of 1-4, how confident are you about describing the three main types of rocks and how they form?

• 1

• 2

• 3

• 4