Geology relative dating activity


There may be a layer missing in the strata, or a set of sedimentary rock on top of metamorphic rock.These interfaces between discontinuous layers of rock are called unconformities.How do we use the Law of Superposition to establish relative dates?Let's look at these rock strata here: We have five layers total.



We follow this same idea, with a few variations, when we talk about cross-cutting relationships in rock.We'll even visit the Grand Canyon to solve the mystery of the Great Unconformity!Imagine that you're a geologist, studying the amazing rock formations of the Grand Canyon.Let's say we find out, through numerical dating, that the rock layer shown above is 70 million years old.

We're not so sure about the next layer down, but the one below it is 100 million years old. Not exactly, but we do know that it's somewhere between 70 and 100 million years old.

Inclusions are always older than the sedimentary rock within which they are found.