Fossils What are fossils FOSSILS are the preserved

Fossils

What are fossils? • FOSSILS are 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.

Recipe for a fossil:

TURN AND TALK! • What type of rock are fossils most likely to be found in? • Why is the most likely – what happens in the other types of rocks?

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? – Is it: • Remains? • Imprints? • Traces? – Lived long ago? – Will it last a long time?

“OK, it’s a fossil. How old is it? ”

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.

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

Geological Time http: //tinyurl. com/dxvpyz