If we use a 24-hour day to represent Earth's history, humans would have existed for the last:
a. 1 minute.
b. 1 hour.
c. 2 hours.
d. 5 hours.
e. 12 hours.
Question 2
The boundaries between the distinct layers found in many sedimentary rocks are called:
a. foliation.
b. regolith.
c. outcrops.
d. rock cycles.
e. bedding planes.