Questions and Answers
What describes the relative age of a rock?
Uses the law of superposition to determine which rock is older or younger.
What feature causes a gap in the geologic record?
Erosion.
What describes the absolute age of a rock?
Is the number of years since it formed.
Which statement about layers A, B, C, and D is accurate?
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What can a geologist conclude from finding tilted sedimentary rock layers?
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In which situation is the principle of cross-cutting relationships useful?
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Which characteristic is shared by extrusions, intrusions, and faults?
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What feature forms at Earth's surface from the cooling of lava?
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What explains one reason why unconformities occur?
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Which three different geologic features help determine the relative ages of rocks by their positions?
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What describes organisms that formed index fossils?
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How do index fossils help scientists?
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What characteristic does a fossil that might make a good index fossil most likely have?
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What is the first step for geologists to compare rock layers at distant locations?
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What describes the law of superposition?
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What describes faults?
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What event is most likely if an index fossil is found at location 1, but not at location 2?
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Study Notes
Relative Dating Concepts
- Relative age describes the age of a rock in relation to another, determined by the law of superposition.
- Erosion creates gaps in the geologic record, resulting in unconformities.
- Absolute age specifies the actual number of years since a rock's formation.
Layer Analysis
- In a sequence of sedimentary rock layers, if layers are labeled A, B, C, and D from the top down, B is younger than C.
- Tilted sedimentary rock layers indicate that they were originally deposited horizontally before being disturbed.
Geologic Principles
- The principle of cross-cutting relationships is utilized when a fault disrupts sedimentary layers, indicating the fault is younger than the layers it intersects.
- Extrusions, intrusions, and faults are all younger than the surrounding rock formations.
Formation and Characteristics
- Extrusions occur when lava cools at Earth's surface.
- Unconformities arise when there is a significant period without sediment deposition.
- Index fossils, which are usually from extinct organisms, are critical for dating and comparing rock layers across different locations.
Fossil Identification and Usage
- Index fossils help geologists relate rock layers across various distances and are typically abundant in specific regions.
- To effectively compare rock layers at separate locations, geologists first identify index fossils present in the layers.
Law of Superposition
- The law of superposition states that, in horizontal rock layers, each layer is younger than the layer beneath it, establishing a chronological sequence.
- Faults are characterized by their ability to cause rocks to fracture and shift.
Organism Distribution Events
- If an index fossil is found in a layer at one location but not in a nearby location of the same relative age, it indicates that the organism likely did not inhabit that area.
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Description
Test your knowledge of relative dating concepts in geology with these flashcards. Learn about the principles, such as the law of superposition and factors affecting the geologic record. Perfect for students in Earth Science or Geology courses.
