Picture of relative dating
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.
What could a geologist say about that section of rock?
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.
Free 5-day trial Discover how geologists study the layers in sedimentary rock to establish relative age.
Learn how inclusions and unconformities can tell us stories about the geologic past.
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 use this type of method all the time to establish relative ages of rocks.Now, what if instead of being horizontal, this rock layer was found in a tilted position?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.The highest layers tell them what happened more recently, and the lowest layers tell them what happened longer ago.