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Metamorphic Rocks — Reading Comprehension

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MS-ESS2-1
MS-ESS3-1

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This engaging middle school science passage introduces students to the fascinating world of metamorphic rocks. Aligned with NGSS standards MS-ESS2-1 and MS-ESS3-1, the text explains how heat and pressure transform existing rocks deep underground, forming new minerals and textures. Students learn about the two primary types of metamorphic rocks—foliated and non-foliated—using familiar examples like slate, gneiss, marble, and quartzite. The passage explores processes such as contact and regional metamorphism, and details the sequence from parent rocks to their metamorphic forms. With a focus on scientific thinking, cause and effect, and real-world implications, the content supports comprehension, analysis, and application. The resource includes a glossary, reading quiz, writing prompts, and graphic organizers, making it ideal for science classrooms. Audio integration supports diverse learners. Keywords include metamorphic rocks, heat, pressure, rock cycle, foliation, and geology.

CONTENT PREVIEW

Metamorphic rocks are an important part of Earth's crust. These rocks form when existing rocks are changed by intense heat, pressure, or chemical processes deep under the surface. Unlike rocks that form directly from magma or from sediments, metamorphic rocks are created by the transformation of other rocks. This transformation, called metamorphism, reveals information about the powerful forces shaping our planet.

How Metamorphic Rocks Form

Metamorphic rocks form through a process that changes the mineral structure and texture of existing rocks. When rocks are buried far beneath Earth's surface, they are exposed to temperatures ranging from 150°C to over 800°C and pressures thousands of times greater than at the surface. These conditions cause atoms and minerals to rearrange, creating new minerals and larger crystals. For example, the clay minerals in the sedimentary rock shale transform into the flat, hard sheets of slate. Metamorphic changes can also occur near plate boundaries where Earth's crust is pushed or pulled, or near magma chambers where heat is especially strong.

Types and Sequences of Metamorphic Rocks

There are two main types of metamorphic rocks: foliated and non-foliated. Foliated rocks, like slate, schist, and gneiss, have mineral grains aligned in bands or layers due to directed pressure. This gives them a striped or banded appearance. Non-foliated rocks, such as marble and quartzite, do not have layers because the minerals grow in random directions. The type of metamorphic rock formed depends on the composition of the parent rock and the conditions of metamorphism. For example, shale can become slate, then schist, and finally gneiss as heat and pressure increase—a process called increasing metamorphic grade. Limestone, rich in calcite, transforms into marble, while sandstone becomes quartzite.

Metamorphism in Action: Contact and Regional

Not all metamorphism occurs the same way. Contact metamorphism happens when rocks are heated by nearby magma, changing only rocks close to the heat source. In contrast, regional metamorphism affects large areas during mountain building, as huge sections of crust are squeezed and heated over millions of years. Regional metamorphism creates most of the world's metamorphic rocks and is responsible for the formation of mountain ranges.

Metamorphic rocks are more than just beautiful stones. They help scientists understand Earth's dynamic processes, the history of plate movements, and the cycling of materials in the crust. Their unique patterns and mineral content are used in construction, art, and even as indicators of valuable resources deep underground.

Interesting Fact: Some of the oldest rocks on Earth are metamorphic, with ages reaching over 4 billion years. These ancient rocks preserve a record of Earth's earliest history!

What causes rocks to become metamorphic rocks?

Heat, pressure, or chemical processesOnly melting and coolingBreaking into small piecesErosion by water

Which of the following is a foliated metamorphic rock?

SlateMarbleQuartziteLimestone

What is the sequence from shale to gneiss called?

Metamorphic gradeRock cycleSedimentationWeathering

What happens to minerals during metamorphism?

They rearrange and form new mineralsThey melt completelyThey break into sandThey dissolve in water

What does 'non-foliated' mean in the context of metamorphic rocks?

The rock has no layers or bandsThe rock is made of sandThe rock is only found near volcanoesThe rock is always soft

What is the main difference between contact and regional metamorphism?

Contact affects small areas near heat; regional affects large areas under pressureContact happens during volcano eruptions; regional happens in oceansContact creates only igneous rocks; regional creates only sedimentary rocksContact makes rocks colder; regional makes rocks softer

Why are metamorphic rocks important for scientists?

They reveal information about Earth's history and processesThey are always shinyThey are easy to find everywhereThey contain dinosaur fossils

True or False: All metamorphic rocks have visible bands or stripes.

TrueFalse

True or False: Marble forms from limestone during metamorphism.

TrueFalse

What is one use of metamorphic rocks in everyday life?

They are used in construction and artThey are only for scientific studyThey are used to make fuelThey are not used by people