What is stratigraphy?

• A. Stratigraphy is the analysis of Earth's sediment layers (strata) to estimate the age of fossils.
• B. Stratigraphy is the study of volcanic activity.
• C. Stratigraphy is the measurement of atmospheric gases.
• D. Stratigraphy is the classification of minerals.

Answer: (A)

Stratigraphy is the study of rock layers and their order to understand the timing of events in Earth's history. By examining sediment layers, scientists determine which layers are older and which are younger, since sediments are laid down in a sequence over time. Fossils within those layers act as time markers, helping to estimate the age range of past organisms and to correlate layers across different locations that share similar fossils. This approach creates a vertical timeline of the past and uses principles like superposition and fossil succession to interpret Earth's history. The description that stratigraphy analyzes sediment layers to estimate fossil ages captures this idea, while topics about volcanic activity, atmospheric gases, or mineral classification belong to other areas of Earth science.