Fossils

Fossils- the preserved remains or evidence of living things

Types of Fossils Original Remains- Unchanged remains of plants and animals Examples Hard parts: Bones, Shells Animals trapped in ice: Wooly Mammoth Animals trapped in tar or in amber

Woolly Mammoth in ice Saber-toothed Tiger Amber with an insect Frog in Amber Woolly Mammoth in ice

Fossilized dinosaur bones in sandstone (sedimentary rock)

The La Brea tar pit in Los Angeles, California is famous for its many fossils! Tar is thick and sticky

Types of Fossils Replaced Remains: Hard parts of plants or animals are replaced by minerals over time. The minerals are in the shape of the organism. This occurs when water containing minerals seeps through the plant/animal material. Petrified wood forms in this way

Petrified Wood Example: Minerals have replaced all of the wood cells and turned this wood into rock!

Ice= Cast Types of Fossils Ice cube tray= Mold Molds and Casts: Impressions and copies Molds are created as mud or sediment becomes rock around dead organisms. Casts are created as minerals get deposited into the molds and then harden. They make a copy of the fossil. Ice= Cast Ice cube tray= Mold

Example: Cast of an Ammonite

Trace Fossils: Evidence of organisms Types of Fossils Trace Fossils: Evidence of organisms Footprints, teeth marks, tunnels Carbonaceous film: thin film of carbon resembling a silhouette of the organism

Index Fossils **An Index fossil is a fossil used to determine the relative age rocks. **Relative age is the age compared to another rock --It is not the true age of the rock --It tells you if it is the same age, or if it is younger or older than another rock.

Requirements To be an Index fossil, you must: 1. Be common (lots of them) 2. Be found in a lot of places worldwide (wide distribution) 3. Exist for a short period of time 4. Unique. Shouldn’t look like other fossils.

Trilobite: Index fossil of Paleozoic Graptolite: Index fossil of the Silurian

Question: Fossils are usually formed when the organism dies and gets buried in mud or sand. As a result, What type of rock are fossils usually found in?

Questions: Why are fossils NOT usually found in igneous rock?

Questions: What 4 settings (environments) could fossils be preserved?

Questions: What are the 5 types of fossils?