Earth History

The preserved remains or traces of an organism that lived in the past

The timeline developed by scientists of the major events and the changes in life during the earth's history

Millions of fossils that have been collected and studied, paint a picture of life in the past.

When an entire species dies out.

The study of earth's past

Fossils from organisms that only lived during a short period of Earth's history. Many fossils of this organism can be found over wide area of Earth.

A key example of an organism used as an index fossil. A hard shelled animal whose body had three section, lived in shallow seas and became extinct during the mass extinction that ended the paleozoic era.

In undisturbed rock layers. The layers on bottom are older than the layers above it.

The age of an object compared to another. Uses terms like older and younger. Is not a number!

Finding the relative age of something like rock layers

Finding EXACTLY how old something is in years.

Finding the absolute age of something.

Using the decay rate of radiometric atoms to date rocks and fossils.

A type of radiometric dating used to date things that used to be alive.

The amount of time it takes for half of the parent atoms to decay into daughter atoms during radiometric dating.