Scientific definition of relative dating

With this in mind geologist have long known that the deeper a sedimentary rock layer is the older it is, but how old?

Although there might be some mineral differences due to the difference in source rock, most sedimentary rock deposited year after year look very similar to one another.

Scientists also use direct evidence from observations of the rock layers themselves to help determine the relative age of rock layers.

This process lead to a system of time containing eons, eras, periods, and epochs all determined by their position in the rock record.

For example, rocks of the Phanerozoic eon are found on top of rocks from the Proterozoic eons therefore rocks of the Phanerozoic are younger than rocks of the Proterozoic.

Time factors of millions and billions of years is difficult even for adults to comprehend.

However, "relative" dating or time can be an easy concept for students to learn.

PALEONTOLOGY, AND in particular the study of dinosaurs, is an exciting topic to people of all ages.

Although most attention in today's world focuses on dinosaurs and why they became extinct, the world of paleontology includes many other interesting organisms which tell us about Earth's past history.

For example, most limestones represent marine environments, whereas, sandstones with ripple marks might indicate a shoreline habitat or a riverbed.

Return to top The study and comparison of exposed rock layers or strata in various parts of the earth led scientists in the early 19th century to propose that the rock layers could be correlated from place to place.

*Earth and Space Science: Fossils provide important evidence of how life and environmental conditions have changed.

The complete "Paleontology and Dinosaurs" module takes approximately four weeks to teach. " activity is a 30-minute introduction to geologic time.

*Life Science: Fossils indicate that many organisms that lived long ago are extinct.

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