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What is a rock?
An aggregate of one or more minerals, a body of undifferentiated mineral matter, or solid organic matter.
Which of the following is NOT a type of rock?
What type of rock forms by solidification of molten rock?
How many types of rocks are found on Earth?
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What is the process by which igneous rocks are formed?
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Igneous rocks can only be formed through volcanic activity.
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What type of igneous rock is formed from magma or volcanic fragments that erupt on the Earth's surface?
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Basalt is an example of which type of igneous rock?
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What is granite classified as?
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What are the classifications of igneous rocks based on texture?
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An igneous rock that has a very dark shade and consists largely of olivine and pyroxene is known as __________.
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Study Notes
Rocks Overview
- Rocks are aggregates of one or more minerals, undifferentiated mineral matter (e.g., obsidian), or solid organic matter (e.g., coal).
- Appearances vary based on composition, grain size, and arrangement, influencing texture and physical properties.
Types of Rocks
- Igneous: Form from solidification of molten rock (magma).
- Sedimentary: Form via lithification of sediment (sand, silt, clay, shells).
- Metamorphic: Form from transformations of preexisting rocks without melting.
Igneous Rocks Formation
- Result from melting, cooling, and crystallization processes.
- Commonly formed during volcanic activity, mantle melting, or along tectonic plate boundaries.
Classification of Igneous Rocks
- Extrusive Rocks: Formed when magma erupts and solidifies on the Earth's surface, resulting in fine-grained texture with small crystals. Examples include basalt, obsidian, and pumice.
- Intrusive Rocks: Formed within the Earth, typically involving slow cooling, leading to large visible interlocking crystals. Examples include granite, gabbro, and diorite.
Structures in Intrusive Igneous Rocks
- Discordant Structures: Cut across existing geological features (e.g., dikes).
- Concordant Structures: Injected parallel to the existing structures (e.g., sills).
Igneous Rock Textures
- Glassy: Smooth texture with no crystal structure.
- Aphanitic: Fine-grained, crystals not visible to the naked eye.
- Phaneritic: Coarse-grained, crystals visible to the naked eye.
- Porphyritic: Mix of large and small crystals.
Types of Igneous Rocks Based on Mineral Composition
- Felsic: Light-colored, high in quartz and potassium feldspar. Example: Granite.
- Intermediate: Medium gray/green, contains amphibole and plagioclase.
- Mafic: Dark gray/black, high in plagioclase and amphibole. Example: Basalt.
- Ultramafic: Very dark, composed primarily of olivine and pyroxene.
Special Rock Characteristics
- Pegmatitic: Crystals larger than 3 cm due to slow cooling.
- Vesicular: Contains holes (vesicles) formed by gas bubbles.
- Amygdaloidal: Vesicles filled with minerals post solidification.
- Pyroclastic: Composed of consolidated volcanic rock fragments.
Rock Utility
- Understanding rock types helps in studying Earth's geological history and formation processes.
Importance of Crystallization
- Crystallization rates influence the size and formation of crystals within the rock, impacting their classification and characteristics.
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Description
This quiz explores the fundamentals of minerals and rocks, including their definitions, characteristics, and classification. Learn about aggregates, volcanic glass, solidified organic matter, and the composition of various rocks like granite.
