Igneous, Sedimentary, and Metamorphic Rocks

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Questions and Answers

What type of rock is formed from the solidification of molten rock?

Igneous (correct)

Sedimentary

Intrusive

Metamorphic

Which of the following is a type of sedimentary rock?

Granite

Limestone (correct)

Basalt

Schist

What characterizes metamorphic rocks?

Made from rock fragments

Result from the alteration of existing rocks under heat and pressure (correct)

Formed from biological material

Cooled quickly on the surface

Which rock type is described as having a layered appearance?

Schist Signup and view all the answers

What is a distinct property of calcite when exposed to hydrochloric acid?

It effervesces or fizzes Signup and view all the answers

Which property would you observe in a mineral demonstrating cleavage?

Smooth, flat surfaces where it breaks Signup and view all the answers

What happens if a mineral shows fracture instead of cleavage?

It breaks irregularly without any flat surfaces Signup and view all the answers

Which rock is an example of an extrusive igneous rock?

Basalt Signup and view all the answers

What is the primary use of the Mohs scale of hardness in mineral identification?

To assess how easily a mineral can be scratched Signup and view all the answers

What does the presence of striations on a mineral's surface indicate?

The mineral is likely a plagioclase feldspar Signup and view all the answers

How can one determine the streak color of a mineral?

By rubbing the mineral on a white porcelain streak plate Signup and view all the answers

What is likely true about a mineral that effervesces when dilute hydrochloric acid is applied?

It is likely composed of carbonates Signup and view all the answers

Which of the following is NOT a characteristic of a true mineral?

It must be man-made Signup and view all the answers

What does the cleavage of a mineral refer to?

The angles between its cleavage planes Signup and view all the answers

Which type of fracture is described as being curved like a shell?

Conchoidal fracture Signup and view all the answers

Why might color not be a reliable property in mineral identification?

Minerals can have different colors due to impurities Signup and view all the answers

What type of mineral texture is characterized by being fine-grained and too small to see individual crystals without magnification?

Aphanitic Signup and view all the answers

Which of the following is a characteristic of intrusive igneous rocks?

Coarse-grained texture with visible crystals Signup and view all the answers

What distinguishes mafic minerals from felsic minerals?

Mafic minerals are rich in magnesium and iron; felsic minerals are rich in silica. Signup and view all the answers

How do the sizes of crystals in a rock relate to the cooling rate of magma?

Smaller crystals indicate faster cooling. Signup and view all the answers

Which type of rock forms from magma that has reached the Earth's surface?

Extrusive rocks Signup and view all the answers

What type of internal structure do minerals exhibit?

Ordered internal structure Signup and view all the answers

What feature signifies an igneous rock as vesicular?

Presence of small holes due to gas bubbles Signup and view all the answers

Where does magma originate?

Within the crust and upper mantle Signup and view all the answers

What occurs at convergent boundaries?

An oceanic plate subducts beneath a continental or another oceanic plate. Signup and view all the answers

How would you categorize a rock that is formed from fragments of pre-existing rocks?

Clastic rocks Signup and view all the answers

What does well-sorted sediment indicate about the transport process?

Grains are similar in size and shape. Signup and view all the answers

What influences the rounding of a grain during transportation?

The distance traveled and the collision with other surfaces. Signup and view all the answers

Which size designation corresponds to very fine grains?

Smaller than 0.0625 mm Signup and view all the answers

What is the role of weathering compared to erosion?

Weathering breaks down rocks into smaller pieces; erosion transports those pieces. Signup and view all the answers

Which type of sediment would you expect to find in a poorly sorted sample?

Grains of various sizes and shapes Signup and view all the answers

Which of the following describes rounded grains?

They have smooth, curved edges from abrasion during transport. Signup and view all the answers

Study Notes

Rock Types

Igneous Rocks: Formed from molten rock (magma or lava).
- Intrusive: Cools slowly underground (e.g., granite).
- Extrusive: Cools quickly on the surface (e.g., basalt).
Sedimentary Rocks: Created from the accumulation and compaction of sediments or the precipitation of minerals.
- Clastic: Made from rock fragments (e.g., sandstone).
- Chemical: Formed from mineral precipitation (e.g., limestone).
- Organic: Composed of biological material (e.g., coal).
Metamorphic Rocks: Result from the alteration of existing rocks under heat and pressure.
- Foliated: Has layered appearance (e.g., schist).
- Non-foliated: Lacks layers (e.g., marble).

Mineral Identification Properties

Cleavage: Smooth, flat surfaces where the mineral breaks (e.g., look for planes).
Fracture: How the mineral breaks if it doesn't show cleavage (e.g., uneven, conchoidal, splintery).
Angle between cleavage planes: Use a protractor or compare to known angles (e.g., 90°, 120°).
Hardness: Use the Mohs scale of hardness to determine the mineral's resistance to scratching (e.g., fingernail, copper penny, glass, steel file).
Luster: How the mineral reflects light (e.g., metallic, glassy, dull).
Streak: The color of the powder left behind when rubbed on a streak plate.
Striations: Fine, parallel lines on the mineral's surface.
Effervescence (Reaction to acid): Fizzing or bubbling when a drop of dilute hydrochloric acid is applied, indicates the presence of carbonates (e.g., calcite, dolomite).
Transparency/Opacity: Hold the mineral up to a light source to determine if it's transparent, opaque, or translucent.
Color: Can be helpful for identification, but not always reliable due to impurities or variations in composition.

Mineral Requirements

Naturally Occurring: Formed through natural geological processes.
Inorganic: Not derived from living organisms.
Solid: Rigid structure at standard temperature and pressure.
Definite Chemical Composition: Specific chemical formula, although variations can occur.
Ordered Internal Structure: Atoms arranged in a repeating pattern.

Igneous Rock Textures

Aphanitic: Fine-grained texture, too small to see crystals without magnification. (Extrusive)
Phaneritic: Coarse-grained texture, crystals visible to the naked eye. (Intrusive)
Vesicular: Contains small holes (vesicles) formed by gas bubbles. Often light and porous. (Extrusive)
Glassy: Smooth, glassy appearance, no visible crystals. Often breaks with a conchoidal fracture. (Extrusive)

Igneous Rock Colors

Mafic: Dark-colored, rich in magnesium and iron (e.g., black or dark green).
Intermediate: Mix of light and dark minerals, often gray or beige.
Felsic: Light-colored, rich in silica (e.g., white, pink, or light gray).

Magma vs. Lava

Magma: Molten rock beneath the Earth's surface.
Lava: Magma that has reached the Earth's surface.

Crystal Size and Rock Formation

Larger crystals indicate slower cooling (intrusive rocks).
Smaller crystals indicate faster cooling (extrusive rocks).

Extrusive vs. Intrusive Rock Formation

Extrusive Rocks: Form on the Earth's surface from volcanic eruptions.
Intrusive Rocks: Form beneath the Earth's surface from magma cooling slowly.

Volcano Locations

Convergent Boundaries: Where an oceanic plate subducts beneath a continental or oceanic plate, leading to volcanic activity.
Divergent Boundaries: Where tectonic plates move apart, allowing magma to rise and create new crust.

Sedimentary Rock Properties

Well-Sorted: Grains are similar in size and shape, indicating natural sorting.
Poorly-Sorted: Grains vary widely in size and shape, indicating a mixed appearance.
Grain Size Very Fine: Smaller than 0.0625 mm (clay).
Grain Size Fine: 0.0625 mm to 0.25 mm (silt).
Grain Size Medium: 0.25 mm to 2 mm (sand).
Grain Size Coarse: 2 mm to 64 mm (granules).
Grain Size Very Coarse: Larger than 64 mm (pebbles, cobbles).
Angular Grains: Sharp edges & corners, indicating limited transport.
Rounded Grains: Smooth, curved edges, indicating longer distance traveled and abrasion.

Sedimentary Rock Types

Biogenic: Formed from organic material.
Chemical: Formed from mineral precipitation from solution.
Clastic: Composed of fragments of pre-existing rocks cemented together.

Grain Rounding and Transport

As grains travel further, they collide with each other and surfaces, causing abrasion and rounding. Longer distance = more rounded grains.

Weathering vs. Erosion

Weathering: The breakdown of rocks, soils, and minerals, through contact with the Earth's atmosphere, water, and biological organisms.
Erosion: The movement of weathered material by natural forces like wind, water, and ice.

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Description

Explore the fascinating world of rocks in this quiz on igneous, sedimentary, and metamorphic types. Learn about their formation, characteristics, and the properties used in mineral identification. Test your knowledge on different rock types and their identification properties!