Questions and Answers
How do sedimentary rocks form?
Sedimentary rocks form primarily by the deposition of sediments under water.
What are the three main types of sedimentary rocks?
Clastic, crystalline, and bioclastic
What is a clast?
A rock fragment
How are clastic sedimentary rocks formed?
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How are clastic sedimentary rocks classified?
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What is the difference between a conglomerate and a breccia?
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How are crystalline sedimentary rocks formed?
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What does saturated mean?
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Describe evaporation and precipitation.
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What does precipitation mean when we are talking about sedimentary rocks?
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How are bioclastic sedimentary rocks formed?
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How was coal formed?
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Describe the temperature and pressure of formation of sedimentary rocks as compared to other rock types.
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Why are sedimentary rocks found as a veneer over much of Earth’s surface?
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Why aren't sedimentary rocks found deep in the Earth?
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Why are sedimentary rocks the only rocks that contain fossils?
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Why are sedimentary rocks often layered?
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Study Notes
Formation of Sedimentary Rocks
- Sedimentary rocks primarily form through the deposition of sediments in water.
- Layers of sediments accumulate over time, leading to rock formation.
Types of Sedimentary Rocks
- Three main types include clastic, crystalline, and bioclastic.
- Clastic rocks are composed of rock fragments; crystalline rocks form from evaporated sea water; bioclastic rocks comprise remnants of living materials.
Clastic Sedimentary Rocks
- Clasts are fragments of rocks that make up clastic sedimentary rocks.
- Formation involves burial, compaction, and cementation of these clasts.
- Classification is based on the size and shape of clasts.
- Conglomerates contain rounded fragments, while breccias have angular fragments.
Crystalline Sedimentary Rocks
- These rocks form via the evaporation of seawater, leading to crystal precipitation.
- Saturated solutions retain as much dissolved substance as possible, influencing mineral deposition.
Processes of Evaporation and Precipitation
- Evaporation of shallow seas leaves behind dissolved minerals as water becomes saturated.
- Excessive evaporation causes precipitation, forming solid crystals from minerals in solution.
Bioclastic Sedimentary Rocks
- Formed from compaction of fragments from previously living organisms or their products.
- Coal is a specific example, originating from compacted, partially decayed plant matter.
Environmental Conditions of Formation
- Sedimentary rocks typically develop at low temperatures and pressures compared to igneous and metamorphic rocks.
- Most sedimentary processes occur near the earth's surface, predominantly underwater.
Distribution and Characteristics of Sedimentary Rocks
- Found as a veneer or surface layer over much of the Earth's terrain due to their formation from deposited layers.
- Rarely located deep within the Earth, as high temperatures and pressures can cause melting or metamorphism.
Fossils in Sedimentary Rocks
- Sedimentary rocks are unique in containing fossils, as the conditions for their formation preserve organic materials.
- Other rock types often destroy or distort fossils during their formation processes.
Layering of Sedimentary Rocks
- Layering occurs because sediments are deposited in successive layers, which are preserved during compaction and cementation.
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Description
Explore the fascinating world of sedimentary rocks with this study set. Learn how they are formed, the different types, and key concepts like clasts and clastic rocks. Perfect for students looking to deepen their understanding of geology.