Questions and Answers
According to the principle of inclusions, what can be concluded if one rock contains pieces of another rock?
The rock containing the pieces is younger than the pieces.
Which rock layer is considered the youngest in a sequence where there is a fault cutting through both an intrusion and rock layers?
The fault
What does it mean for a rock layer to be 'intruded'?
Magma has entered or forced its way into the rock layer.
Based on the information provided, what can be inferred about a rock layer with many inclusions?
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If a fault cuts across a rock layer and an intrusion, which of the following statements is true?
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What do inclusions in rocks suggest about their relative ages?
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'Horizontal' as an adjective in geology refers to which characteristic of a formation?
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'Lateral' as derived from Latin lateralis means:
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'Disturb' as a verb in scientific vocabulary specifically means:
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'Magma' as a noun refers to:
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Study Notes
Principles of Relative-Age Dating
- The principle of superposition states that in undisturbed rock layers, the oldest rocks are on the bottom and each layer is younger than the layer below it.
- The principle of original horizontality states that most rock-forming materials are deposited in horizontal layers, and if the layers are tilted or folded, they were originally deposited horizontally.
Principles of Rock Formation
- The principle of lateral continuity states that sediments are deposited in large, flat sheets that continue in all lateral directions until they thin out or meet a barrier.
- The principle of cross-cutting relationships states that if one geologic feature cuts across another feature, the feature that it cuts across is older.
Faults and Inclusions
- A fracture is a break in a rock formation, and if rocks move along a fracture line, the fracture is called a fault.
- If one rock contains pieces of another rock, the rock containing the pieces is younger than the pieces, according to the principle of inclusions.
Geologic Time
- Nicolaus Steno developed a set of principles to compare the ages of rock layers, known as Steno's principles, which include superposition, original horizontality, lateral continuity, and cross-cutting relationships.
- Modern geologists have added a fifth principle, the principle of inclusions, to the principles of relative-age dating.
Vocabulary
- Disturb: to change the position or order of something
- Horizontal: flat and level
- Lateral: from Latin lateralis, means “belonging to the side”
- Intrusion: the entry of magma into or between rock formations; the igneous rock formed
- Magma: molten rock inside Earth
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