How is the geologic column used in relative dating
The work predated Darwin's theory, and any accurate idea of how old the earth was.
Early quantitative attempts to develop an absolute age of the earth tried to use the build up of salt in the oceans, or the thermal cooling of the earth from an molten mass done by Lord Kelvin got huge numbers from the human perspective but woefully undershot the true age.
By looking at these layers, taking rock samples and analyzing them, we can figure out a lot about the history of the area. At the start of the Proterozoic layers, there are areas where large periods of history are missing.
This is called the Great Unconformity---the result of tectonic activity that caused some of the rock to be worn away and the direction of the layers to be tilted. We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities.
These layers can go back as far as billions of years in some cases, and provide valuable information about the earth's history.
One of the best and most visited examples of a geologic column is the Grand Canyon.
It was a period of time when the collision of the earth's tectonic plates caused this part of the rock to be pushed upwards and exposed to the air---above the water level, just like the Grand Canyon is now.When that happens, no new rock is being formed and instead the rock is being worn away.This violent pushing upwards as two plates collided also caused the rock to become tilted.A geologic column is a series of layers of different types of rock, placed by the settling of sediments over millions of years, often when the rock was a sea bed. At the Grand Canyon, the layers of rock stretch back an impressive 1.84 billion years.Many places that used to be sea beds are now on land and can easily be studied by humans. These include rocks from the Paleozoic and Proterozoic eras.