Fossils relative absolute dating


28-May-2017 20:03

By studying fossils, evidence for evolution is revealed.

Paleontologists are scientists who study fossils to learn about life in the past.

On Earth, we have a very powerful method of relative age dating: fossil assemblages.

Paleontologists have examined layered sequences of fossil-bearing rocks all over the world, and noted where in those sequences certain fossils appear and disappear.

Paleontologists compare the features of species from different periods in history.

With this information, they try to understand how species have evolved over millions of years (Figure below). Fossil evidence, depicted by the skeletal fragments, demonstrates evolutionary milestones in this process.

This technique measures how much of the radioactive materials in each rock layer have broken down (Figure below).

Radiometric dating has been used to determine that the oldest known rocks on Earth are between 4 and 5 billion years old.

This all has to do with describing how long ago something happened. There are several ways we figure out relative ages.Here's the next step in that journey: the Geologic Time Scales of Earth and the Moon.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. When you say that I am 38 years old or that the dinosaurs died out 65 million years ago, or that the solar system formed 4.6 billion years ago, those are absolute ages.Until recently, fossils were the main source of evidence for evolution (Figurebelow).

Through studying fossils, we now know that today’s organisms look much different in many cases than those that were alive in the past.The simplest is the law of superposition: if thing A is deposited on top of (or cuts across, or obliterates) thing B, then thing B must have been there already when thing A happened, so thing B is older than thing A.We have no idea how much older thing B is, we just know that it's older.That's why geologic time is usually diagramed in tall columnar diagrams like this.



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Figure 2. How relative dating of events and radiometric numeric dates are combined to produce a calibrated geological time scale. In this example, the data.… continue reading »


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