For example, based on the primate fossil record, scientists know that living primates evolved from fossil primates and that this evolutionary history took tens of millions of years.
By comparing fossils of different primate species, scientists can examine how features changed and how primates evolved through time.
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.
Absolute dating is the process of determining an age on a specified chronology in archaeology and geology.
Some scientists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies an unwarranted certainty of accuracy.
In a way this field, called geochronology, is some of the purest detective work earth scientists do.
Absolute age dating is like saying you are 15 years old and your grandfather is 77 years old.Unlike people, you can’t really guess the age of a rock from looking at it.Yet, you’ve heard the news: Earth is 4.6 billion years old. That corn cob found in an ancient Native American fire pit is 1,000 years old. Geologic age dating—assigning an age to materials—is an entire discipline of its own.Precise isotopic ages are called absolute ages, since they date the timing of events not relative to each other but as the time elapsed between a rock-forming event and the present.Absolute dating by means of uranium and lead isotopes has...Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.