Relative dating description

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.

The most obvious feature of sedimentary rock is its layering.

This feature is produced by changes in deposition over time.

Your goal is to study the smooth, parallel layers of rock to learn how the land built up over geologic time.

Now imagine that you come upon a formation like this: What do you think of it? How can you make any conclusions about rock layers that make such a crazy arrangement?

Prior to the discovery of radiometric dating which provided a means of absolute dating in the early 20th century, archaeologists and geologists used this technique to determine ages of materials.From top to bottom: Rounded tan domes of the Navajo Sandstone, layered red Kayenta Formation, cliff-forming, vertically jointed, red Wingate Sandstone, slope-forming, purplish Chinle Formation, layered, lighter-red Moenkopi Formation, and white, layered Cutler Formation sandstone.Picture from Glen Canyon National Recreation Area, Utah.Sequencing the rock layers will show students how paleontologists use fossils to give relative dates to rock strata.Once students begin to grasp "relative" dating, they can extend their knowledge of geologic time by exploring radiometric dating and developing a timeline of Earth's history.

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