Relative dating sequence of events

08-Feb-2018 16:42 by 10 Comments

Relative dating sequence of events

These major concepts are part of the Denver Earth Science Project's "Paleontology and Dinosaurs" module written for students in grades 7-10.

The first card in the sequence has "Card 1, Set A" in the lower left-hand corner and represents the bottom of the sequence.

INTRODUCTION Scientists have good evidence that the earth is very old, approximately four and one-half billion years old.

Scientific measurements such as radiometric dating use the natural radioactivity of certain elements found in rocks to help determine their age.

If certain fossils are typically found only in a particular rock unit and are found in many places worldwide, they may be useful as index or guide fossils in determining the age of undated strata.

By using this information from rock formations in various parts of the world and correlating the studies, scientists have been able to establish the geologic time scale.

By matching partial sequences, the truly oldest layers with fossils can be worked out.

By correlating fossils from various parts of the world, scientists are able to give relative ages to particular strata. Relative dating tells scientists if a rock layer is "older" or "younger" than another.

Locally, physical characteristics of rocks can be compared and correlated.

On a larger scale, even between continents, fossil evidence can help in correlating rock layers.

If the letters "T" and "C" represent fossils in the oldest rock layer, they are the oldest fossils, or the first fossils formed in the past for this sequence of rock layers. Now, look for a card that has either a "T" or "C" written on it.

Since this card has a common letter with the first card, it must go on top of the "TC" card.

This would also mean that fossils found in the deepest layer of rocks in an area would represent the oldest forms of life in that particular rock formation.

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