Rock Cycle

Rock Cycle

Middle School

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Learning Objectives

• Define the three main rock types: igneous, sedimentary, and metamorphic.

• Describe the processes that form each of the three rock types.

• Explain how rocks change from one type to another in the rock cycle.

• Identify examples and common uses for each of the rock types.

Key Vocabulary

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Geologist

A scientist who studies rocks to understand the Earth's history and its geological processes using physcial and chemical characters.

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Igneous Rock

A type of rock that is formed from the cooling and hardening of molten rock.

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Sedimentary Rock

A rock type formed by the compaction and cementation of small pieces of other rocks.

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Metamorphic Rock

A rock transformed by extreme heat and intense pressure without melting into magma.

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Sediment

Small, solid pieces of material such as sand that come from rocks or living things.

The Three Types of Rocks

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Igneous Rocks

• Formed from the cooling and hardening of hot, molten rock.

• This molten rock is called magma when it is inside Earth.

• It is called lava when it erupts on the Earth’s surface.

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Sedimentary Rocks

• Formed from particles of other rocks, minerals, or organic matter.

• These particles are called sediments, which build up in layers.

• Over time, these layers are pressed and cemented together into rock.

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Metamorphic Rocks

• Formed when existing rocks are changed by great heat and pressure.

• The original rock can be igneous, sedimentary, or another metamorphic rock.

• This process changes the rock’s texture and its mineral composition.

Multiple Choice

According to geologists, what three characteristics are primarily used to classify rocks?

• Color, texture, and mineral composition

• Size, weight, and location

• Age, hardness, and shape

• Smell, taste, and temperature

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Types of Igneous Rocks

Intrusive Rocks

• ​Formed from magma cooling slowly and hardening beneath the Earth's surface.

• ​​The slow cooling process allows for the formation of large crystals.

• ​Granite is a common example of this type of igneous rock.

Extrusive Rocks

• ​Formed from lava that erupts and cools rapidly on the Earth's surface.

• ​​The rapid cooling means that crystals are very small or do not form.

• ​Common examples of extrusive rocks include Basalt and Obsidian.

Multiple Choice

What is the main difference between the formation of intrusive and extrusive igneous rocks?

• Intrusive rocks form on the surface, while extrusive rocks form beneath the surface.

• Intrusive rocks form from lava, while extrusive rocks form from magma.

• Intrusive rocks form from magma hardening beneath the surface, while extrusive rocks form from lava cooling on the surface.

• Intrusive rocks cool rapidly, while extrusive rocks cool slowly.

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Sedimentary Rocks

• Sedimentary rocks form from sediments compacted and cemented together over time.

• ​Sediments are small pieces of rock or material from living things.

• Weathering and erosion break down rocks to create these sediment particles.

• Common examples of these rocks include limestone, conglomerate, and sandstone.

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Multiple Choice

What are the two primary processes that lead to the formation of sedimentary rocks?

• Heat and pressure

• Melting and cooling

• Compaction and cementation

• Eruption and hardening

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Metamorphic Rocks

• Metamorphic rocks are created when existing rocks change due to heat and pressure.

• This transformation happens deep underground without the original rock melting.

• It is caused by pressure from rock layers or colliding tectonic plates.

• Common examples of these rocks include Marble, Gneiss, and Slate.

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Multiple Choice

What two major forces cause rocks to change and become metamorphic rocks?

• Weathering and erosion

• Compaction and cementation

• Extreme heat and pressure

• Cooling and hardening

The Rock Cycle

• The rock cycle shows how rocks change from one type to another.

• Heat and pressure create metamorphic rocks deep within the Earth.

• Melted rock, or magma, cools and solidifies to form igneous rock.

Multiple Choice

Which statement best describes the rock cycle?

• It is an ongoing process where rocks are continuously changed from one type to another.

• It is a one-way process where igneous rocks become sedimentary, then metamorphic.

• It is a process that only happens deep within the Earth's crust.

• It is a process that ends once a rock becomes metamorphic.

Uses of Rocks

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Igneous Rocks

• ​Due to their durability, they are often used for creating monuments.

• ​​They are also used to make statues and as building materials.

• ​Granite is a popular choice for kitchen countertops and flooring tiles.

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Sedimentary Rocks

• ​Limestone is a key ingredient used in the manufacturing of cement.

• ​​This type of rock is also used to make sticks of chalk.

• ​Shale, another sedimentary rock, is commonly used for making bricks.

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Metamorphic Rocks

• ​These rocks are valued for building materials and for creating artwork.

• ​​Slate, a type of metamorphic rock, is used for making roofing.

• ​They are also used for creating the ballast for railroad tracks.

Multiple Choice

Which type of rock is commonly used for manufacturing chalk and cement?

• Igneous

• Sedimentary

• Metamorphic

• Obsidian

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Common Misconceptions

Misconception	Correction
Rocks are permanent and do not change.	The rock cycle shows that rocks are constantly changing from one form to another.
Metamorphic rocks are formed by melting.	Metamorphic rocks are changed by heat and pressure, but they do not melt.
Fossils can be found in all types of rock.	Fossils are almost exclusively found in sedimentary rocks.

Multiple Choice

How does the formation of intrusive igneous rocks differ from the formation of metamorphic rocks?

• Intrusive igneous rocks are formed by melting and cooling, while metamorphic rocks are changed by heat and pressure without melting.

• Intrusive igneous rocks are formed by compaction, while metamorphic rocks are formed by weathering.

• Both are formed by intense heat, but only metamorphic rocks involve pressure.

• Both are formed from lava, but at different temperatures.

Multiple Choice

Based on how they are formed, why are fossils most likely to be found in sedimentary rocks rather than the other types?

• The gentle process of sediment compaction and cementation can preserve remains

• Sedimentary rocks are softer, making it easier for fossils to form inside them.

• Fossils are only formed from materials that make up sediments.

• The other rock types are too old to contain fossils.

Multiple Choice

A piece of slate (a metamorphic rock) is pushed deep into the Earth, where temperatures are high enough to turn it into molten rock. If this molten rock then cools and hardens, what new type of rock will be created?

• Igneous rock

• Sedimentary rock

• Another type of metamorphic rock

• It will remain slate

Multiple Choice

Imagine a basalt rock (extrusive igneous) on the surface of the Earth. Trace the steps it would need to go through to become a sedimentary rock like sandstone.

• The basalt must undergo weathering and erosion to become sediment, which is then compacted and cemented.

• The basalt must be subjected to extreme heat and pressure to change its form.

• The basalt must be melted into magma and then re-cooled on the surface.

• The basalt must be buried and then exposed to hot fluids.

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Summary

• There are three main types of rocks: igneous, sedimentary, and metamorphic.

• Igneous rocks form from the cooling of molten magma or lava.

• Sedimentary rocks form from the compaction and cementation of sediments.

• Metamorphic rocks form when existing rocks are changed by extreme heat and pressure.

• The rock cycle is the continuous process through which rocks change from one type to another.

• Each rock type has specific properties that make it useful for different purposes, from construction to artwork.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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