Question

A geologist finds some tilted sedimentary rock layers.

Which conclusions can the geologist draw by looking at the rock layers? Check all that apply.

Their absolute age is 600 million years.
They were tilted after they were deposited.
They were originally deposited horizontally.
The youngest layer was originally deposited as the bottom layer.
Their relative ages have not changed even though they are tilted.

Answer 1

Answer: They were tilted after they were deposited; they were originally deposited horizontally; the youngest layer was originally deposited as the bottom layer; their relative ages have not changed even though they are tilted.

Geologic tilting is the process by which the Earth's rock layers begin to slant irregularly. This can be caused by vertical or horizontal faults, angular unconformity and disturbances on the Earth's magnetic field.

A geologist cannot know the exact age of a rock layer just from looking at it. The information can only be obtained by other methods, to an approximation. He can, however, know that the youngest layer is the one that was originally at the bottom. He also knows that the relative age of the layers has not changed.

Angular unconformity occurs when a new layer of sedimentary rock is deposited on layers that were already tilted, thus exacerbating it. By looking at the layer carefully, the geologist can find out whether the tilting happened while the sediments were being deposited, or afterwards. He can also know which way they were originally deposited by studying characteristics such as cracks and ripple marks.

Answer 2

The correct answers are B) they were tilted after they were deposited, C) they were originally deposited horizontally, and E) their relative ages have not changed even though they are tilted.

The conclusions the geologist can draw by looking at the rock layers are: They were tilted after they were deposited, they were originally deposited horizontally, and their relative ages have not changed even though they are tilted.

The geologist that finds these sedimentary rock layers can apply some considerations in Geology that help understands the way rocks are placed. For instance, the consideration of Superposition that helps geologist to understand that the rock at the top is the newest and the rock at the bottom is the oldest. The other consideration is of Original Horizontality that indicates that before being deformed by time or Earth movements, the rocks were placed horizontally.