Question

how do layers b and d compare in age? if rock layers between b and d have eroded away,what is the boundary between b and d called

Answer 1

What are layers b and d? We don't have your graphic.

Answer 2

they are layers pictured. B is one layer closer to the ground than D

Answer 3

but D is only a small patch beneath the ground

Answer 4

1.b
2.a
3.a
4.b
5.c
6.a
7.a
8.c
9.a
10.c
11.c
12.b
13.a
14.a
15.D is older than B because B pushes on D. The boundary is called an unconformity.
16. The half life is 28 years because it is the time it takes for one half of the original amount of strontium-90 to decay.
17.essay
Trust me I got 100% on my test.
Bye, Jascha Heifetz