Quiz on relative dating securedating com review

Free 5-day trial Use this quiz and worksheet to assess your understanding of the techniques geologists use to establish relative dating and the relationships that occurred over geologic time periods.

Now imagine that you come upon a formation like this: What do you think of it? How can you make any conclusions about rock layers that make such a crazy arrangement?

Geologists establish the age of rocks in two ways: numerical dating and relative dating.

Following the Principle of Original Horizontality, he could say that whatever forces caused the deformation, like an earthquake, must have occurred after the formation of all the rock strata.

Since we assume all the layers were originally horizontal, then anything that made them not horizontal had to have happened after the fact.

We follow this same idea, with a few variations, when we talk about cross-cutting relationships in rock.

Let's say, in this set of rock strata, that we found a single intrusion of igneous rock punching through the sedimentary layers.

It sounds like common sense to you and me, but geologists have to define the Principle of Original Horizontality in order to make assumptions about the relative ages of sedimentary rocks. Say you have a layer of mud accumulating at the bottom of a lake. More sediment accumulates from the leaf litter and waste of the forest, until you have a second layer.

Once we assume that all rock layers were originally horizontal, we can make another assumption: that the oldest rock layers are furthest toward the bottom, and the youngest rock layers are closest to the top. The forest layer is younger than the mud layer, right? When scientists look at sedimentary rock strata, they essentially see a timeline stretching backwards through history.

Imagine that you're a geologist, studying the amazing rock formations of the Grand Canyon.

Your goal is to study the smooth, parallel layers of rock to learn how the land built up over geologic time.

Learn how inclusions and unconformities can tell us stories about the geologic past.

Tags: , ,