After a rock layer is eroded, which additional event must occur to create an unconformity, or a gap in the geologic record?

a. an earthquake or motion along a fault.
b. new deposits of sediment must build up on the eroded area.
c. folding of sedimentary rock layers.
d. a volcanic eruption.

Is this A? My lesson gives a definition for unconformity as "a rock or sediment surface separating two layers of different ages."

Sam, quit trolling and worry about yourself kid.

I mean to say C.

I think it's B.

Sam how can you do the same test 3 years later?

To determine which additional event must occur to create an unconformity, let's analyze the options provided.

a. an earthquake or motion along a fault.
Movement along a fault or an earthquake can disrupt the layers of rock but may not necessarily create an unconformity. Unconformities refer to gaps in the geologic record, not simply the displacement of rock layers.

b. new deposits of sediment must build up on the eroded area.
This option is the most likely answer. After a rock layer is eroded, the next step to create an unconformity is the deposition of new sediment on the eroded area. This new deposit of sediment would effectively create a gap or surface separating the eroded layer and the newly formed layer.

c. folding of sedimentary rock layers.
Folding of sedimentary rock layers does not necessarily create an unconformity. While folding can alter the appearance of rock layers, it does not generate a gap in the geologic record.

d. a volcanic eruption.
While a volcanic eruption can introduce new layers of volcanic rock, it does not create an unconformity unless there is subsequent erosion and deposition of sediment on top of the volcanic material.

Based on the given definition and the options provided, the correct answer would be b. new deposits of sediment must build up on the eroded area. After erosion, the deposition of new sediment would result in an unconformity, creating a gap in the geologic record.

You are not aloud to use outside help when doing a test. The answer is not C. That is all I can help with. I know what school you are in, I just did this test.