Fossils REMAINS OF LIVING THINGS THAT HAVE BEEN BURIED BY SEDIMENT. SEDIMENT HARDENS PRESERVING SHAPE OF ORGANISM.

Paleontologist A smart guy/gal who studies fossils!

Sedimentary rock Rock made from hardened sediment (broken pieces). Often found near water (lakes, oceans, mud bogs…) where sediment tends to build up. Bones, teeth, shells, seeds, stems are often left behind.

Types of fossils 1) Petrified – remains turned to stone by being replaced by minerals

Types of fossils 2) Molds and casts- Most common fossil Mold- imprint/shape is preserved, hollow Cast- copy of the shape of the organism

Types of fossils 3) Carbon film- Thin coating of carbon on a rock Gasses escape from organism leaving carbon behind

Types of fossils 4) Trace fossils Evidence of activity of organism Feces, footprint, trails How did it live?

Why study fossils? Fossils can indicate what life was like in the past…climate, geology, landforms, geography… Fossils can tell us how organisms have changed over time (evolved)

Like fossils?

“Rocks of Ages” Relative Age vs. Absolute Age Relative Age- “age of rock” in relation to others surrounding it Absolute Age- # of years since the rock formed (difficult to get an EXACT date)

Position of rock layers 1) Law of Superposition – lower layers older than upper layers (they’ve been there longer)

Position of rock layers 2) Extrusion– lava hardens on surface (so newer.) AKA volcano 3) Intrusion- younger than rocks below.

Position of rock layers 4) Fault- younger than the rock it cuts through

Index fossils Fossil that was only around for a brief time. Gives relative age of rock around it. Ex-Trilobites

Geologic Time Let’s review… Absolute vs. Relative time Methods to identify how old a rock is

Time is always relative…

Precambrian time 544 million years ago to 4.6 billion years 88% of Earth’s history Formation of Earth, molten…then water planet…formation of primary atmosphere…

Eras Three major eras since Precambrian time 1- Paleozoic – (oldest) 544 million years -245 million years 2- Mesozoic 245 million years – 66.4 million years 3- Cenozoic (current) 66.4 million years- present

Periods Smaller units within eras Millions of years Examples: Jurassic, Triassic, Cretaceous periods

How the Earth was Made Part II On a piece of notebook paper down the following time periods. As the video comes to each of these time periods write down 2 facts about that time period on your paper. 3.4 billion years ago (bya) 2.5 bya 1.5 bya 1.0 bya 700 million years ago (mya) 550 mya 300 mya

Paleozoic era mya “Explosion of life”- Cambrian explosion Marine life Trilobites, Brachiopods Jawless fish Vertebrates (organisms with a backbone) Plants Insects Amphibians- lives part of life on land, part in water Reptiles- scaly skin and lay eggs with leathery shells

And then… Mass extinction 95% of life in the oceans disappeared Fish, reptiles survived “Permian extinction”

Mesozoic era Triassic, Jurassic and Cretaceous periods Conifers “Age of reptiles” Mammals Archaeopteryx “ancient winged thing” Flowering plants Fruits/seeds

And then… Mass extinction 65 mya Asteroid K/T boundary

Cenozoic era Mammals thrived Grasses Ice ages Humans