Six laws of relative dating

Different species of ammonites lived at different times within the Mesozoic, so identifying a fossil species can help narrow down when a rock was formed.

Correlation can involve matching an undated rock with a dated one at another location.

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Once they are able to manipulate the cards into the correct sequence, they are asked to do a similar sequencing activity using fossil pictures printed on "rock layer" cards.

Sequencing the rock layers will show students how paleontologists use fossils to give relative dates to rock strata.

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

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

Some fossils, called index fossils, are particularly useful in correlating rocks.

For a fossil to be a good index fossil, it needs to have lived during one specific time period, be easy to identify and have been abundant and found in many places. If you find ammonites in a rock in the South Island and also in a rock in the North Island, you can say that both rocks are Mesozoic.

Relative dating does not provide actual numerical dates for the rocks.

Fossils are important for working out the relative ages of sedimentary rocks.

Correlation with them has helped geologists date many New Zealand rocks, including those containing dinosaurs.

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