ROCK LAYERS
Which principle states that sedimentary rock layers become younger from bottom to top?
A. Lateral continuity
B. Faunal succession
C. Superposition
D. Crosscutting relationships
A. Lateral continuity
Which type of dating determines only the order in which geological events occurred?
A. Absolute dating
B. Relative dating
C. Radioactive dating
D. Radiometric measurement
B. Relative dating
Which is the longest subdivision of geologic time?
A. Epoch
B. Period
C. Era
D. Eon
D. Eon
A fault cuts across several layers of rock. Which formed first?
A. The fault
B. The rock layers
C. Both formed together
D. The youngest rock layer
B. The rock layers
What happens to daughter isotopes as radioactive decay continues in a rock?
A. Their amount decreases over time.
B. Their amount remains unchanged.
C. Their amount increases over time.
D. Their amount disappears after one half-life.
C. Their amount increases over time.
A geologist finds evidence of the first vascular land plants in a rock layer. According to the geologic time scale, which period does the evidence indicate?
A. Cambrian
B. Ordovician
C. Silurian
D. Devonian
C. Silurian
A geologist finds matching rock layers on opposite sides of a valley. Which principle supports the conclusion that the layers were originally connected?
A. Superposition
B. Original horizontality
C. Lateral continuity
D. Crosscutting relationships
C. Lateral continuity
A radioactive isotope has a half-life of 10 million years. A rock originally contained 100% parent isotope. How much parent isotope remains after 20 million years?
A. 75%
B. 50%
C. 25%
D. 10%
C. 25%
Which of the following shows the CORRECT match between a geologic eon and a major event in Earth’s history?
A. Hadean Eon — First life forms evolved
B. Archean Eon — Earth’s crust solidified
C. Proterozoic Eon — Multicelled animals appeared
D. Phanerozoic Eon — Earth’s crust solidified
C. Proterozoic Eon — Multicelled animals appeared
A dike cuts through Layers A, B, and C but does not cut Layer D, which lies above them. Which conclusion is best supported?
A. The dike formed before Layers A, B, and C.
B. The dike formed after Layer D.
C. The dike formed after A, B, and C but before D.
D. The dike and all four layers formed at the same time.
C. The dike formed after A, B, and C but before D.
A radioactive isotope has a half-life of 1 million years. A rock contains 25% of the original parent isotope. How many half-lives have passed?
A. One
B. Two
C. Three
D. Four
B. Two
Which sequence correctly arranges these events from oldest to youngest?
A. First amphibians → first fishes → first vascular plants → first dinosaurs
B. First vascular plants → first fishes → first amphibians → first dinosaurs
C. First fishes → first vascular plants → first amphibians → first dinosaurs
D. First fishes → first amphibians → first vascular plants → first dinosaurs
C. First fishes → first vascular plants → first amphibians → first dinosaurs
Three sedimentary layers contain fossils that appeared in the following sequence through time: Fossil X → Fossil Y → Fossil Z. Layer A contains Fossil X, while Layer B contains Fossil Z. Which conclusion is best supported?
A. Layer A is younger than Layer B.
B. Layer A and Layer B formed at the same time.
C. Layer A is older than Layer B.
D. The fossils cannot be used to compare the layers.
C. Layer A is older than Layer B.
A geologist measures the isotopes in an igneous rock and finds that only 12.5% of the original parent isotope remains. The isotope has a half-life of 4 million years. Approximately how old is the rock?
A. 4 million years
B. 8 million years
C. 12 million years
D. 16 million years
C. 12 million years
A geologist is studying a rock containing evidence of the first fishes and first chordates. Another rock contains evidence of the first amphibians and diversification of jawed fishes. Which conclusion correctly compares their ages?
A. The rock with amphibians is older because Devonian precedes Cambrian.
B. The rock with fishes is older because Cambrian precedes Devonian.
C. Both rocks formed during the same period of the Paleozoic Era.
D. The rock with fishes is younger because more complex organisms appeared later.
B. The rock with fishes is older because Cambrian precedes Devonian.