Chapter 29, Problem 2TE

Why don’t all rock formations show a continuous sequence from the beginning of time to the present?

To determine

The reason for rock formations being discontinuous from beginning of time to the present.

Answer to Problem 2TE

The reason for rock formations being discontinuous are due to processes such as erosion, crustal uplift, folding and faulting.

Explanation of Solution

The deposition of sedimentary rocks forms the temporal sequence of rock structures. However, the rock formations are not entirely continuous in terms of their sequence due to processes that happen parallel to deposition. The gaps that occur in the sequence are known as unconformities. There are two kinds of unconformities which are due to the differences in the parallel processes. Sedimentary rock is formed when successive layers of sediments lie on each other. But every rock is subjected to geological forces, due to which their formation is not continuous. This can be due to the process of earthquakes, faulting, etcetera, or crustal uplift. Mountains are a series of rocks that are uplifted because of the movement of plates.

Disconformities are associated with igneous and metamorphic rocks on which localized sedimentary deposits are observed. This happens due to folding and faulting, along with erosion. It is a time gap between parallel layers and that of sedimentary rock.

Conclusion:

Therefore, the reason for rock formations being discontinuous in terms of temporal sequence are due to processes such as erosion, crustal uplift, folding and faulting.