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Relative dating does not provide actual numerical dates for the rocks.
Fossils are important for working out the relative ages of sedimentary rocks.
The Modern Geologic Time Scale, as shown above, documents intervals of geologic time relative to one another, and has been continuously developed and updated over the last two centuries.
In addition to the relative dating of periods in Earth's history for which we have rocks preserved, geologists are now able to assign absolute age dates to critical intervals.
Prior to the late 17th century, geologic time was thought to be the same as historical time.
Archbishop James Ussher of Armagh, Ireland, 1654, added up generations from the Old Testament and determined that Earth formed on October 23, 4004 BCE.
How do we know this and how do we know the ages of other events in Earth history?
Arizona Geology Virtual Tourist: Click Your Way Through Arizona Scenery -- Another type of Virtual Field Trip of a real place.
Movies created by draping geologic maps over topography -- a great way to teach geologic maps!
Lake Powell area (near Page) -- MSS satellite image draped over digital topography Virtual Field Trips of Invented Places Painted Canyon -- A Geologic Wonderland!
These images, done with Bryce4, are of an invented, but representative, Southwestern canyon. Some of the files are large (not very compressed), especially the cool Quick Time VR panoramas (pivot 360 degrees).