Recall that sedimentary rock is composed of They complicate the task of relative dating, because they don't give an accurate picture of what happened in geologic history. Inclusions and Unconformities Sometimes, geologists find strange things inside the strata, like chunks of metamorphic or igneous rock.
Plus, get practice tests, quizzes, and personalized coaching to help you succeed. The tops of their folds are completely gone where the sandstones have replaced them. Deserts What controls the motion of sand in sand dunes? Students learn about river processes in these two activities: Click More Information below. Let's say we find out, through numerical dating, that the rock layer shown above is 70 million years old.