Rules of relative dating
Because these units are used according to the rules of the metric system, the M in Ma and the G in Ga must be capitalized, and the k in ka must not be capitalized.
Geologist are often trying to learn more about Earth and its history.
Underlying assumptions are 1) that Faunal Succession is based on the observation that animals and animal communities that are preserved in sedimentary rocks change noticeably as geologic time passes (evolution).
It was first recognized by William Smith, a British Surveyor, who while working on open cuts of canals, railroads, and roads, noticed that the fossils change systematically from the older towards the younger rocks.
Rocks from several localities have been dated at more than 3 billion years 3. The grains composing detrital sedimentary rocks are not the same age as the rock in which they occur b.
Geologic time covers the whole sweep of earth's history, from how and when the earth first formed, to everything that has happened on, in, and to the planet since then, right up to now.
It is widely accepted that the Earth is about 4.5 billion years old. For example, the Colorado river has eroded away parts of the Columbia plateau.
How do we know this and how do we know the ages of other events in Earth history?
Comparing the ratio of parent to daughter yields the age of the sample 1.
Radiometric dating is a complex procedure that requires precise measurement 2.
Geologists analyze geologic time in two different ways: in terms of relative geologic age, and in terms of absolute (or numeric) geologic age.
The combination of these two types of geologic ages makes a complete record of earth's geologic history in terms of the order of events and in terms of how many years ago each event occurred.