Geologic column dating

In fact, sedimentary rocks are, in a sense, trash from the Earth's surface deposited in basins.Principle of Original Horizontality Sedimentary strata are deposited in layers that are horizontal or nearly horizontal, parallel to or nearly parallel to the Earth's surface.From the beginning of this course, we have stated that the Earth is about 4.6 billion years old.How do we know this and how do we know the ages of other events in Earth history?The goal of this lecture is come to come to a scientific understanding of geologic time and the age of the Earth.In order to do so we will have to understand the following: To better understand these concepts, let's look at an archeological example: Imagine we are a group of archeologists studying two different trash pits recently discovered on the Tulane University campus and at the Audubon Zoo (where they all aksed for you).

But, since the rhyolite dike does not cut across the shale, we know the shale is younger than the rhyolite dike.Once these age relations were worked out, another principle fell into place - the principle of fossil succession.We discuss the 7 principles of stratigraphy first and then see how these apply to fossils.In either case, the inclusions had to be present before they could be included in the younger rock, therefore, the inclusions represent fragments of an older rock.This principle is often useful for distinguishing between a lava flow and a sill.By carefully digging, we have found that each trash pit shows a sequence of layers.

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