1. Topic: How Old is Old? Geologic Time Broadcast 4: February 7, 2001 Mrs. Joan Linsley

2. Relative vs. Absolute Time Relative: the age of a rock layer in relation to other nearby layers. The precise length of geologic time represented by any layer is often unknown. Absolute: the age of a rock or mineral in numbers of years.

3. Geologic Time 1.8 5.0 23 38 54 65 135 192 280

4. Terms/Tools for Determining Age Biostratigraphical Unit: definition of the boundaries of a rock layer based on the ages of fossils within it Lithostratigraphical Unit: definition of the boundaries of a rock layer based on the physical characteristics of the rocks within Chronostratigraphical Unit: division of a section of rock based on the absolute ages of the rocks within it Geochronology: development of a time- line of events relating to the deposition or creation of rocks in a given area

5. Use of Fossils Fossils provide a record of the slow, progressive development of life. Through the use of index fossils, one may identify a particular layer of rock wherever it is exposed. Scientists use fossils to identify ages of rocks throughout the world.

6. Guest Dr. Michael Howell Paleontologist University of South Carolina

7. Fossils

8. Bio/Lithostratigraphy

9. Time for: Ask A Question!!