Video Transcript
Which of the following best
describes a nonconformity? (A) An unconformity that exists
between two bodies of igneous rock. (B) An unconformity that exists
between igneous and metamorphic rocks. (C) An unconformity that exists
between two parallel layers of sedimentary rock. (D) An unconformity that exists
between two nonparallel sedimentary layers. (E) An unconformity that exists
between sedimentary rocks and igneous or metamorphic rocks.
To answer this question, we must
first understand what an unconformity is. An unconformity is a geological
structure that represents a break in geological time. This means a period of time where
no sediment has been deposited. It is represented as an
unconformable surface between two different sets of rocks.
There are a number of different
types of unconformities, but this question focuses on nonconformities. Nonconformities are often located
where old mountain belts once stood. Over time, these mountain belts
were eroded, exposing the igneous and metamorphic rocks at their core. Once exposed at Earth’s surface,
sedimentary rocks could be deposited unconformably on top of them. The unconformable surface between
the metamorphic or igneous rocks and sedimentary rocks is referred to as a
nonconformity.
So, a nonconformity can be
described as an unconformity that exists between sedimentary rocks and igneous or
metamorphic rocks.
