Review What are the 5 ways to absolute age materials?

Review - Isotopes (SPECIAL ATOMS) Atoms that belong to the same element but have different atomic masses are isotopes of one another. Isotopes of the same element have the same # of protons and electrons but a different # of neutrons. All elements have isotopes. Isotopes are the reason why atomic masses are decimals and not whole #’s. Some isotopes are radioisotopes, which means they are unstable and their nucleus breaks apart. Release energy. Turns the isotope into an atom of a different element.

Add to table of contents: Fossil Lab Pg. 42 Fossils Pg. 43 Open Earth Science Textbook to page 197

Fossils Pg. 43 Fossils – the remains of animals or plants that lived in a previous geological time. Fossils are an important part of relative and absolute aging of rocks. We already learned which type of rock fossils are most likely to found in. What was it?

How fossils form: 1. Mummification – in dry areas where bacteria don’t survive. 2. Amber – insects trapped in sticky tree sap. 3. Tar seeps – animals get stuck in sticky tar. LaBrea Tar Pits in California

1910 Today

Only 1 human has ever been found in the LaBrea Tar Pit a 9,000 year old woman(17-25 yr old)

Don’t Write On February 18, 2009, George C. Page Museum formally announced the 2006 discovery of 16 fossil deposits which had been removed from the ground during the construction of an underground parking garage for the Los Angeles County Museum of Art next to the tar pits.[9] Among the finds are remains of a saber-toothed cat, six dire wolves, bison, horses, a giant ground sloth, turtles, snails, clams, millipedes, fish, gophers, and an American lion.[9][10] Also discovered is a nearly intact mammoth skeleton, nicknamed Zed; the only pieces missing are a rear leg, a vertebra and the top of its skull, which was sheared off by construction equipment in preparation to build the parking structure.

4. Freezing – too cold for bacteria Otzi and wooly mammoths 5. Petrification – minerals replace organic material to form a mineral replica. Petrified wood

6. Imprints – carbon-rich film left from plants and fish. 7. Molds & Casts – empty cavities(molds) fill with sand or mud and hardens(cast) 8. Coprolites – fossilized dung

9. Gastroliths – stones in digestive systems to grind up food. While some fossil gastroliths are rounded and polished, many stones in living birds are not polished at all. Gastroliths associated with dinosaur fossils can weigh several kilograms. Stones swallowed by ostriches can exceed a length of 10 centimetres (3.9 in). Also found in chickens and crocodiles.

Why are most fossils found formed from the bones or shells of animals?

Index fossil – only occur in rock layers of a particular age. Scientists can use index fossils to relative and absolute age rock layers.