Base your answers to questions one through three on the geologic cross-section below, which shows rock units one through seven that have not been overturned. Some of the rock units contain New York State index fossils. And uncomfortably exists between rock units five and six. 1. What evidence shown in the cross-section indicates that the basalt rock unit is the youngest rock unit?

2. Bed rock from which entire geologic time period is missing between rock units five and six?

3. Describe one characteristic of volcanic ash layer is an index fossils that make both of them good geologic time markers