DCA 2 Review Questions

Which geological principle states that sedimentary layers are originally deposited horizontally?

• Original horizontality

• Lateral continuity

• Superposition

• Cross-cutting relationships

Answer explanation

The principle of original horizontality states that sedimentary layers are initially deposited in horizontal positions. This means that any tilting or folding occurs after their deposition, making it the correct choice.

Which mass extinction event is considered the largest in Earth's history?

• Permian-Triassic

• Cretaceous-Paleogene

• Triassic-Jurassic

• Ordovician-Silurian

Answer explanation

The Permian-Triassic extinction, occurring around 252 million years ago, is the largest mass extinction event, wiping out approximately 90% of species. It significantly reshaped Earth's biodiversity.

Tags

NGSS.MS-LS4-1

What assumption is critical for accurate radiometric dating?

• Uniform initial isotope amounts

• Steady deposition rates

• Constant decay rates

• Equal mass of parent and daughter isotopes

Answer explanation

Constant decay rates are essential for accurate radiometric dating, as they ensure that the rate at which parent isotopes decay into daughter isotopes remains unchanged over time, allowing for reliable age calculations.

What does the law of cross-cutting relationships indicate about an intrusion in rock layers?

• Older than the surrounding layers

• The same age as adjacent strata

• Younger than the rocks it cuts through

• An unrelated time event

Answer explanation

The law of cross-cutting relationships states that an intrusion is younger than the rock layers it cuts through, as it must form after the existing layers have already been deposited.

Which observation supports the theory of continental drift?

• Matching fossil records

• Identical climate patterns

• Uniform rock color

• Similar magnetic fields

Answer explanation

Matching fossil records support the theory of continental drift by showing that similar species existed on widely separated continents, indicating they were once connected.

Tags

NGSS.MS-ESS2-3

NGSS.MS-LS4-1

What process wears down mountains by breaking rocks into smaller particles?

• Sedimentation

• Metamorphism

• Erosion

• Deposition

Answer explanation

Erosion is the process that wears down mountains by breaking rocks into smaller particles through natural forces like wind and water. It is distinct from sedimentation, metamorphism, and deposition.

Which principle states that in undisturbed rock layers, the lower layers are older than the upper ones?

• Cross-cutting relationships

• Superposition

• Original horizontality

• Uniformitarianism

Answer explanation

The principle of superposition states that in undisturbed rock layers, the oldest layers are at the bottom and the youngest are at the top. This is why the correct answer is superposition.

Tags

NGSS.MS-ESS1-4

Which eon marks the formation of Earth approximately 4.6 billion years ago?

• Archean

• Proterozoic

• Hadean

• Phanerozoic

Answer explanation

The Hadean eon marks the time of Earth's formation, approximately 4.6 billion years ago. It is characterized by the planet's initial development and the formation of its earliest crust.

Tags

NGSS.MS-ESS1-4

After one half-life, what percent of the original radioactive isotope remains?

• 25%

• 75%

• 50%

• 100%

Answer explanation

After one half-life, half of the original radioactive isotope has decayed. Therefore, 50% of the original amount remains, making 50% the correct answer.

Tags

NGSS.HS-PS1-8

Which era in the Geological Time Scale is known for the rise of mammals?

• Cenozoic

• Paleozoic

• Mesozoic

• Precambrian

Answer explanation

The Cenozoic era is known as the 'Age of Mammals' because it marks the time when mammals diversified and became the dominant land animals following the extinction of the dinosaurs at the end of the Mesozoic era.

Tags

NGSS.MS-ESS1-4