Rock Classification and Formation
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What primarily composes igneous rocks?

  • Sediments from other rocks
  • Recrystallization due to heat and pressure
  • Organic materials and minerals
  • Magma cooling and crystallization (correct)

    • Which of the following best describes volcanic (extrusive) igneous rocks?

  • They undergo chemical alteration due to pressure.
  • They are created from cooled lava on Earth's surface. (correct)
  • They form from the lithification of sediments.
  • They form deep underground with a coarse texture.

    • What type of rock is basalt categorized as?

  • Volcanic extrusive igneous rock (correct)
  • Sedimentary rock
  • Metamorphic rock
  • Plutonic igneous rock

    • How do plutonic (intrusive) igneous rocks typically form?

    <p>By slow cooling of magma underground</p> Signup and view all the answers

    Which of the following statements about granite is accurate?

    <p>It is a coarse-grained intrusions rock, commonly light in color.</p> Signup and view all the answers

    What distinguishes a dike from a sill in igneous rocks?

    <p>A dike has a vertical orientation, while a sill is horizontal or inclined.</p> Signup and view all the answers

    What is the primary engineering property of granite?

    <p>Excellent frost resistance</p> Signup and view all the answers

    What term refers to the formation process of sedimentary rocks?

    <p>Lithification of sediments from other rocks</p> Signup and view all the answers

    What is the range of resistance that igneous rocks must have to be used in material engineering services?

    <p>1500-2000 kg/cm2</p> Signup and view all the answers

    Which of the following types of sedimentary rocks is formed by the cementation process?

    <p>Limestone</p> Signup and view all the answers

    What does the term 'consolidation' refer to in the context of sedimentary rock formation?

    <p>The conversion of loose sediments into hard rock</p> Signup and view all the answers

    Which of the following describes the process of compaction in sedimentary rock formation?

    <p>The squeezing out of water and solidifying the mass</p> Signup and view all the answers

    What causes the degradation of igneous rocks, affecting their credibility?

    <p>Clay mineralization from weathering</p> Signup and view all the answers

    Which of the following statements about sedimentary rocks is NOT correct?

    <p>They can only form in oceanic environments.</p> Signup and view all the answers

    Which sedimentary rock is primarily known for being formed by crystallization?

    <p>Limestone</p> Signup and view all the answers

    Why is it important to inspect volcanic rocks before construction?

    <p>To evaluate their physical properties</p> Signup and view all the answers

    What is the primary component of diorite?

    <p>Plagioclase feldspar</p> Signup and view all the answers

    Which of the following igneous rocks is most abundant?

    <p>Granite</p> Signup and view all the answers

    What characteristic texture is formed by slow cooling of magma?

    <p>Coarse-crystalline</p> Signup and view all the answers

    What is the compressive strength of granite on average?

    <p>24,500 psi</p> Signup and view all the answers

    Which mineral is least likely to be present in syenite?

    <p>Quartz</p> Signup and view all the answers

    What is a key property of plutonic rocks?

    <p>They exhibit high resistance to breakage and pressure</p> Signup and view all the answers

    What distinguishes obsidian from granite despite their same chemical composition?

    <p>Crystal formation</p> Signup and view all the answers

    What is the term used to describe the size, shape, and arrangement of mineral grains in a rock?

    <p>Texture</p> Signup and view all the answers

    What characteristic defines foliated metamorphic rocks?

    <p>They exhibit bands of minerals in parallel layers.</p> Signup and view all the answers

    Which metamorphic process is specifically associated with mountain building?

    <p>Regional metamorphism</p> Signup and view all the answers

    What is the primary mineral composition of quartzite?

    <p>Quartz</p> Signup and view all the answers

    Which type of metamorphism is driven by temperature changes within the host rock?

    <p>Contact or thermal metamorphism</p> Signup and view all the answers

    What causes the foliation in metamorphic rocks?

    <p>The rotation and alignment of platy and elongated minerals.</p> Signup and view all the answers

    Which of the following is a non-foliated metamorphic rock?

    <p>Marble</p> Signup and view all the answers

    What happens if the melting point of a rock is reached during metamorphism?

    <p>The rock becomes an igneous rock.</p> Signup and view all the answers

    Which of the following best describes hydrothermal metamorphism?

    <p>Chemical alterations happen due to hot, ion-rich water.</p> Signup and view all the answers

    What is the main reason foliated metamorphic rocks are not preferred as construction materials?

    <p>Their strength decreases along the foliation planes.</p> Signup and view all the answers

    Which of the following characteristics makes marble ideal for building materials?

    <p>It has interlocking calcite crystals.</p> Signup and view all the answers

    What can be a significant hazard when constructing in schist-rich regions?

    <p>The potential for shifts in the excavation due to schistosity.</p> Signup and view all the answers

    In what way do metamorphic rocks respond to favorable climatic conditions?

    <p>They show an immediate reaction to changes in volume and pressure.</p> Signup and view all the answers

    What is a significant factor regarding massive gneisses in construction?

    <p>They facilitate large underground openings safely.</p> Signup and view all the answers

    What issue can arise from schistosized and competing gneisses in construction?

    <p>They can cause stability problems in underground openings.</p> Signup and view all the answers

    What effect do clay minerals have on the strength of foliated metamorphic rocks?

    <p>They cause strength reduction when exposed to moisture.</p> Signup and view all the answers

    What is a common characteristic of metamorphic rocks that affects their use in construction?

    <p>They can experience rapid changes under shifting conditions.</p> Signup and view all the answers

    Study Notes

    Introduction to Rocks

    • Rocks are aggregates of mineral particles and can include organic materials.
    • Minerals serve as the fundamental components of rocks.
    • Geological layers include: Bedrock → Outcrop → Regolith → Soils.

    Rock Classification

    • Igneous Rocks: Formed from the cooling and crystallization of magma.
    • Sedimentary Rocks: Created through lithification of sediments from other rocks.
    • Metamorphic Rocks: Result from recrystallization due to heat, pressure, and chemical alteration.

    Igneous Rocks

    • Volcanic (Extrusive) Igneous Rocks: Form on Earth's surface where lava cools, e.g., basalt.
      • Basalt is dark and fine-grained, prevalent on ocean floors.
    • Plutonic (Intrusive) Igneous Rocks: Form deep underground as magma cools slowly, e.g., granite.
      • Granite is the most common plutonic rock, coarse-grained and often light-colored.
    • Hypabyssal Rocks: Form close to the surface in sheet-like bodies called sills or dykes.

    Sills and Dikes

    • Sill: An igneous layer that runs parallel to rock strata; can vary in thickness.
    • Dike: A vertical igneous body that cuts across rock layers; varying thickness from a few centimeters to several meters.

    Common Igneous Rocks

    • Granite: Light-colored, coarse-grained; contains feldspar and quartz.
      • Known for hardness, frost resistance, and compressive strength (average 24,500 psi).
      • Used in structural applications, such as flooring tiles.
    • Diorite: Coarse-grained intrusive rock made of plagioclase feldspar and hornblende.
      • Used primarily for decorative purposes.
    • Syenite: Contains primarily potassium feldspar (80-85%); rare in commercial use.

    Texture of Igneous Rocks

    • Texture refers to the size, shape, and arrangement of mineral grains.
    • Types include coarse-crystalline, fine-grained, cryptocrystalline, and glassy.
    • Cooling rates impact texture: slow cooling leads to crystallization, while rapid cooling results in glassy textures.

    Importance of Igneous Rocks in Engineering

    • Plutonic rocks offer high resistance to breakage and pressure, suitable for engineering applications.
    • Volcanic rocks have variable physical properties; thorough inspection necessary for construction use.
    • Degrading volcanic tuffs and breccias can undermine structural integrity.

    Sedimentary Rocks

    • Formed from layers of sediments deposited in bodies of water, covering 70-80% of Earth's land area.
    • Lithification processes: compaction, cementation, and crystallization convert loose sediments into hard rocks.
    • Common sedimentary rocks include limestone, shale, sandstone, and conglomerate.

    Types of Metamorphism

    • Contact Metamorphism: Caused by an increase in temperature due to nearby hot magma.
    • Regional Metamorphism: Related to mountain-building activities.
    • Burial Metamorphism: Occurs deep beneath thick sedimentary layers.
    • Hydrothermal Metamorphism: Involves chemical changes from hot, ion-rich waters.

    Metamorphic Rock Textures

    • Foliated Rocks: Display parallel bands of minerals, formed under directional pressure.
    • Non-foliated Rocks: Lack layered texture, formed under minimal stress.

    Key Metamorphic Rocks

    • Slate: Forms from shale under heat and pressure, has fine layers and easily splits.
    • Schist: Features shiny layers due to platy minerals.
    • Gneiss: Exhibits bands of light and dark minerals from granite.
    • Marble: Result of limestone recrystallization.
    • Quartzite: Formed from the transformation of sandstone into a dense quartz mass.

    Engineering Properties of Metamorphic Rocks

    • Foliated rocks are generally weak for construction due to mineral alignment along planes.
    • Marble is favored for building materials due to stability and aesthetics.
    • Massive gneisses are suitable for various large underground constructions, while schist poses risks for stability in excavations.

    Rock Recycling

    • The rock cycle is a continuous process where rocks are transformed into different types over geological time.

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    Lecture Notes: Rocks and Minerals Part 1 PDF

    Description

    This quiz covers the basics of rock classification, including igneous, sedimentary, and metamorphic rocks. Understand how these rocks are formed through processes such as cooling, lithification, and recrystallization. Test your knowledge on the relationships between minerals and rock formation.

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