A few days ago, I wrote a post about the basins of the Moon -- a result of a trip down a rabbit hole of book research. In the science of geology, there are two main ways we use to describe how old a thing is or how long ago an event took place. There are absolute ages and there are relative ages. People love absolute ages.
Absolute dating — Science Learning Hub
As we learned in the previous lesson, index fossils and superposition are effective methods of determining the relative age of objects. In other words, you can use superposition to tell you that one rock layer is older than another. To accomplish this, scientists use a variety of evidence, from tree rings to the amounts of radioactive materials in a rock. In regions outside the tropics, trees grow more quickly during the warm summer months than during the cooler winter. Each dark band represents a winter; by counting rings it is possible to find the age of the tree Figure The width of a series of growth rings can give clues to past climates and various disruptions such as forest fires.
Explore This Park. The eroded cliffs reveal 1. The oldest rocks exposed in the canyon are ancient, 1, million years old. Conversely, the canyon itself is geologically young, having been carved in the last 6 million years. An appreciation of geologic time places geologic topics such as geomorphology, the origin and evolution of the Colorado River, stratigraphy, historical geology, and paleontology in context.
About the Book. Student Resources. Chapter 1. Chapter 2.