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Questions and Answers
What is the primary process through which metamorphic rocks are formed?
What is the primary process through which metamorphic rocks are formed?
Igneous rocks can form when pressure is increased on existing rock.
Igneous rocks can form when pressure is increased on existing rock.
False
What type of igneous rock is formed when magma cools slowly beneath the Earth's surface?
What type of igneous rock is formed when magma cools slowly beneath the Earth's surface?
Plutonic rock
Which of the following processes transforms igneous rock into sedimentary rock?
Which of the following processes transforms igneous rock into sedimentary rock?
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Obsidian is typically classified as a _____ rock because it forms from the rapid cooling of molten rock.
Obsidian is typically classified as a _____ rock because it forms from the rapid cooling of molten rock.
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Match the following types of igneous rocks with their characteristics:
Match the following types of igneous rocks with their characteristics:
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Metamorphic rocks are formed directly from other metamorphic rocks.
Metamorphic rocks are formed directly from other metamorphic rocks.
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What are the three main classifications of rocks?
What are the three main classifications of rocks?
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Sedimentary rocks transform into metamorphic rocks through continuous ______ and pressure.
Sedimentary rocks transform into metamorphic rocks through continuous ______ and pressure.
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Match each type of rock with its formation process:
Match each type of rock with its formation process:
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Study Notes
Petrology
- Scientific study of rocks, defined as solid mixtures of minerals or organic matter.
- Classification of rocks: igneous, sedimentary, and metamorphic based on their formation process.
Rock Formation and Classification
- Rocks categorized by formation, composition, and texture.
- Igneous rocks form from cooled magma; sedimentary rocks from accumulated sediments; metamorphic rocks from heat and pressure transformations.
The Rock Cycle
- Illustrates the transformation of one type of rock material to another through geological processes.
- Involves interactions between the geosphere, hydrosphere, atmosphere, and biosphere.
- Processes in the rock cycle include weathering, erosion, deposition, compaction, and cementation.
Transformation Processes
- Igneous to Sedimentary: Weathering and erosion lead to sediments being deposited, compacted, and cemented.
- Sedimentary to Metamorphic: Heating and pressure transform sedimentary rocks into metamorphic rocks.
- Metamorphic to Igneous: Cooling and crystallization of magma forms igneous rocks.
Igneous Rocks
- Form when magma cools and solidifies; can occur due to heating, pressure release, or composition change.
- Textural classification:
- Plutonic (Intrusive): Coarse-grained, cool slowly beneath the surface (e.g., granite).
- Volcanic (Extrusive): Fine-grained, cool quickly at the surface (e.g., basalt).
- Compositional classification:
- Mafic: Dark minerals, rich in iron and magnesium.
- Felsic: Light minerals, rich in aluminum and silica.
Sedimentary Rocks
- Form from weathering, erosion, and deposition of sediments at or near the Earth's surface without heat and pressure.
- Layered structures (strata) due to stratification processes.
- Types include:
- Clastic: Fragments of rock cemented together (e.g., breccia).
- Chemical: Minerals crystallized from solution (e.g., limestone).
- Organic: Derived from accumulated biological materials (e.g., coal).
Metamorphic Rocks
- Form through changes in temperature and pressure, usually deep in the Earth.
- Types of metamorphism:
- Contact Metamorphism: Heating by nearby magma leads to mineral changes.
- Regional Metamorphism: Pressure builds in rocks deeper in the Earth due to tectonic activity.
- Textural classification:
- Foliated: Aligned mineral grains (e.g., gneiss).
- Non-Foliated: Randomly arranged minerals (e.g., marble).
Key Minerals and Composition
- Hornfels: Fine-grained non-foliated metamorphic rock from contact metamorphism.
- Gneiss: Banded appearance from foliation and typically contains quartz or feldspar.
- Marble: Non-foliated formed from limestone, primarily composed of calcium carbonate.
Rock Identification Examples
- Obsidian: Mafic, fine-grained, extrusive volcanic glass.
- Breccia: Clastic rock with large angular fragments cemented together.
- Coal: Organic sedimentary rock, significant as a fossil fuel.
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