How Are Metamorphic Rocks Formed? — Reading Comprehension

Grades

Standards

MS-ESS2-3
RI.6.1
RI.7.4
RI.8.2

About This Reader

This science passage explains how metamorphic rocks form through metamorphism, detailing the effects of heat (150°C-1,000°C) and pressure on existing rocks. It describes regional metamorphism (large-scale) and contact metamorphism (near magma), with examples like shale transforming to slate and limestone becoming marble. The text highlights foliation and crystalline textures, while connecting metamorphic rocks to tectonic activity and Earth's history. Aligns with NGSS MS-ESS2-3 (Earth's systems) and CCSS RI.6.1 (textual evidence). The passage emphasizes real-world applications of metamorphic rocks like marble in construction and garnet schist as abrasives, making complex geological processes accessible for middle school learners.

CONTENT PREVIEW

Metamorphic rocks are created when existing rocks transform under extreme heat and pressure deep within Earth's crust. Unlike igneous rocks (formed from molten magma) or sedimentary rocks (made from compressed sediments), metamorphic rocks change while remaining solid. This process, called metamorphism, alters both the texture and mineral composition of the original rock.

Heat and Pressure: The Key Factors

Metamorphism occurs when rocks are subjected to:

● High temperatures (150°C–1,000°C), often from nearby magma or Earth's internal heat.

● Intense pressure from overlying rock layers or tectonic plate collisions.
For example, shale, a sedimentary rock, becomes slate when compressed, while limestone transforms into marble under heat.

Types of Metamorphism

1. Regional Metamorphism: Covers large areas where tectonic forces squeeze rocks (e.g., forming gneiss from granite).

2. Contact Metamorphism: Occurs when rocks touch magma, "baking" them (e.g., creating hornfels near lava flows).

Visible Changes

Metamorphic rocks often develop:

● Foliation: Layers or bands from aligned minerals (seen in schist or slate).

● Crystalline textures: Interlocking mineral grains (like in quartzite or marble).

Why It Matters

These rocks reveal Earth's history, showing where mountains formed or continents collided. They’re also valuable resources—marble and slate are used in construction, while garnet-rich schist serves as abrasives.

Metamorphic rocks prove Earth’s crust is dynamic, constantly reshaping under powerful forces.

What is the main idea of this passage?

How volcanoes create igneous rocksThe process of sedimentary rock formationHow heat and pressure transform existing rocks into metamorphic rocksWhere to find valuable minerals in nature

What is metamorphism?

The melting of rocks into magmaThe weathering of rocks at Earth's surfaceThe transformation of rocks while remaining solidThe compression of sediments into layers

Which factor does NOT contribute to metamorphism?

High temperatures (150°C-1,000°C)Exposure to wind and rainIntense pressure from tectonic platesHeat from nearby magma

What happens to shale during metamorphism?

It melts into lavaIt becomes slateIt turns into sandstoneIt forms granite

What is foliation?

The melting point of mineralsLayers or bands formed by aligned mineralsThe process of rock erosionCracks caused by earthquakes

Which type of metamorphism occurs over large areas?

Contact metamorphismRegional metamorphismSurface metamorphismVolcanic metamorphism

What valuable resource comes from metamorphic rocks?

Coal for energyMarble for constructionOil for fuelSand for glass

Why are metamorphic rocks important to geologists?

They reveal Earth's history of mountain formationThey are the main source of fossilsThey form most of Earth's surfaceThey create new tectonic plates