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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.

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.

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

Other times, geologists discover patterns in rock layers that give them confusing information.

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

Imagine that you're a geologist, studying the amazing rock formations of the Grand Canyon.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.As a member, you'll also get unlimited access to over 79,000 lessons in math, English, science, history, and more.Plus, get practice tests, quizzes, and personalized coaching to help you succeed.

It's called the Principle of Original Horizontality, and it just means what it sounds like: that all rock layers were originally horizontal. As you can imagine, regular sediments, like sand, silt, and clay, tend to accumulate over a wide area with a generally consistent thickness.