1. Fossils

2. What are fossils? Fossils - the preserved remains or traces of animals, plants, and other organisms that lived long ago. When an organism dies, hard parts of the animal (bones, teeth, shells, etc.) can be preserved in rock. – Layers of sediment form rock around the specimen, quickly preserving the remains. Over many years, the sediment gets pressed into rock. – Soft parts disintegrate away, leaving only the hard parts. Fossils tell us when, where, and how organisms lived.

5. Fossil? Not a fossil? On your worksheet, we will be looking at whether each object is or is not a fossil. Does it meet the criteria for being a fossil? – Remains? – Imprints? – Traces? – Lived long ago? – Will it last a long time?

6. “OK, it’s a fossil. How old is it?”

7. How many ways can you think to find the age of a fossil? Carbon dating and fossil record are just two ways of determining the age of fossils. Carbon dating uses a radioactive form of the element carbon to date dead organisms. – But it’s unreliable if the specimen is over 40,000 years old. The fossil record looks at the layers of rock to determine which layers are older than others. These layers are called “strata.” – The oldest rock layers are the ones that got laid down first, or the ones at the bottom. – Fossils in the oldest layers will be the oldest fossils.

10. Geological Time Earth has been around for a LONG time. – 4.6 billion years, by our estimates This time is divided up into sections called EONS. – Eons are broken up into ERAS. Eras are broken down into PERIODS. – Periods are broken into EPOCHS and AGES. – Each of these sections lasts millions of years. – In order of length (from longest to shortest): eon > era > period > epoch (>) age