Absolute and relative dating in geology Free stranger sex video chat
To determine the relative age of different rocks, geologists start with the assumption that unless something has happened, in a sequence of sedimentary rock layers, the newer rock layers will be on top of older ones. This rule is common sense, but it serves as a powerful reference point.
Geologists draw on it and other basic principles ( to determine the relative ages of rocks or features such as faults.
Relative age dating also means paying attention to crosscutting relationships.
Say for example that a volcanic dike, or a fault, cuts across several sedimentary layers, or maybe through another volcanic rock type.
With absolute age dating, you get a real age in actual years.
For example, which is older, the bricks in a building or the building itself?
Are there repairs or cracks in the sidewalk that came after the sidewalk was built?
On the other hand, the half-life of the isotope potassium 40 as it decays to argon is 1.26 billion years.
So carbon 14 is used to date materials that aren’t that old geologically, say in the tens of thousands of years, while potassium-argon dating can be used to determine the ages of much older materials, in the millions and billions year range.