Question

select the correct answer. unless a series of sedimentary rock layers has been overturned, which layer is usually the oldest?
a. the layer on the top
b. the layer with the most minerals
c. the layer with the most fossils
d. the layer on the bottom
e. the igneous intrusion (dike)

Explanation:

In sedimentary rock formation, the principle of superposition states that in undisturbed (not overturned) layers, older layers are deposited first and lie beneath younger layers. So the bottom layer is usually the oldest. Option A is wrong as top layers are younger. Options B and C relate to mineral or fossil content, not age determination. Option E (igneous intrusion) is younger than the layers it intrudes.

Answer:

D. the layer on the bottom