Unit 7 - Relative Dating and Fossils Chapter 9 – Views of Earth’s Past Section 9.1 – Earth’s past is revealed in Rocks and Fossils

Rocks, fossils, and original remains give clues about the past. Mountain formation, earthquakes, and other changes in Earth’s surface Dinosaurs Reptiles Lived 200,000,000 years ago Became extinct 65,000,000 years ago DO YOU KNOW WHY?

Scientist believe that a giant asteroid crashed into the Earth causing huge changes in the atmosphere, possibly an ICE AGE.

Fossils Preserved traces or remains of living things from long ago. Shells, bones, and teeth Actual organism (original remains), part of an organism, or an impression of an organism Found where conditions prevent decomposition Ice Amber Tar

Fossils Limited information due to decomposition Hard items are more easily preserved Rock fossils form in sedimentary rock. Igneous rock never contain fossils

Mold Fossil Visible shape that was left after an animal or plant was buried in sediment and then decayed Cast Fossil When a hollow mold get filled with minerals, it becomes a solid model of in the shape of the organism Petrified would Stone likeness of a tree left when minerals carried by water take the place of the tree cells

Carbon Films Visible layer of carbon left behind when a dead plant or animal decays Trace Fossils Preserved footprints, trails, animal holes, and even feces; Are compared to what is known about modern animals

Fossils and other natural evidence show changes in life and the environment. Read Part 1 of Page 292 Tree Rings Width of a tree ring tells how much the tree grows in a year Thin rings suggests a dry year while a thick ring suggests a wet year Ice Cores Tubular sample of ice that shows how the layers have built up over time Scientists observe trapped air and determine information about volcanic eruptions or how long an ice period or warm period lasted

Homework Page 293 #1-4

Please take out your homework. Bell Ringer #13 Tuesday, March 29, 2017 Why might ancient lakes and sea beds be rich sources of fossils? The hard parts of water organisms, such as shells, bones, and teeth drop to the bottom and get covered by sediment in layers over time. Questions and answers! Please take out your homework.

Homework Page 293 #1-4 1. What can rock fossils and original remains show about Earth’s past? They can show what organisms were alive in the past, how they lived, and how Earth’s environment has changed 2. Why do rock fossils form in sedimentary rock and not in igneous rock? The heat of molten rock destroys the remains of dead plants and animals Questions and answers!

Homework Page 293 #1-4 3. How do tree rings and ice cores help scientist understand how Earth has changed over time? Tree rings show wet and dry years. Ice cores show how the air has changed and when volcanic eruptions have occurred. 4. If you uncovered fossils of tropical fish and palm trees, what could you say about the environment at the time the fossils formed? The environment was probably a tropical shore line. Questions and answers!

Unit 7 - Relative Dating and Fossils Chapter 9 – Views of Earth’s Past Section 9.2 – Rocks Provide a Timeline for Earth

Layers of Sedimentary rock show age. Relative Age Age of an event or object in relation to other events or objects Bottom layer of rock forms first so it is the oldest If undisturbed , top layer is the youngest Tectonic plate movement can disturb rock layers Igneous rock can also disturb sedimentary rock

Index Fossils Fossils of organisms that were common, that lived in many areas and that existed only during specific spans of time. In relative dating, other fossils can be compared to index fossils to determine when the organism existed.

Radioactive dating can show actual age Radioactivity The breakdown of unstable elements into another form (isotope) of that element Half-life The rate of change for a radioactive element The length of time it takes for half of the atoms in a radioactive element to change from one form to another

Using absolute and Relative age

Homework Page 301 #1-4

Please take out your homework. Bell Ringer #14 Thursday, March 30, 2017 A rock contains a radioactive element with a half life of 100 million years. Tests show that the rock has gone through three half lives. How old is the rock? 300,000,000 years Questions and answers! Please take out your homework.

Homework Page 301 #1-4 1. What can you tell from undisturbed rock layers? Discuss the concept of relative age in your answer. You can tell the relative age of rock layers because sedimentary rock forms in layers, with the oldest at the bottom and the youngest at the top 2. How can index fossils help scientists determine the ages of rock layers? The approximate age of a rock can be determined by comparing it to the age of other index fossils. Questions and answers!

Homework Page 301 #1-4 3. What property of radioactive elements makes them useful for determining absolute age? Particular radioactive elements always break down at the same rate into another form 2. 4. What are some things in your life for which you only know the relative age? A flat screen TV may be one example Questions and answers!

Bell Ringer #15 Friday, March 31, 2017 HAPPY FRIDAY. HAVE A SAFE A FABULOUS SPRING BREAK! New Bell Ringer Policy Keep your own Bell Ringer Notebook Bell Ringer Questions are valid Test Questions Questions and answers! Please take out your homework.

Worksheet 9.1 and 9.2 9.1 1a. Remains of mammoths have been preserved in _____. Ice 1b. A _____ may form when an animal is buried in sediment and then decays. Mold 1c. _____ is the stone fossil of a tree. Petrified wood 1d. A _____ is a type of fossil found in rock that may show detailed images even of soft parts of plants and animals. Carbon film

Worksheet 9.1 and 9.2 9.1 1e. Original remains of insects may be found in hardened tree resin called _____. Amber 1f. The original remains of ancient animals such as sabertooth cats have been preserved in _____. Tar 1g. Sand or sediment can harden in a mold to create a _____. Cast fossil 1h. A fossilized footprint, trail or animal hole is called a _____. Trace fossil

Worksheet 9.1 and 9.2 9.1 2. In what ways are tree rings and ice cores alike? Different? They both are like timelines that help scientists study the past. Both show layers that indicate what the climate was like in the past. Tree rings show whether climate was wet or dry. Ice cores show times that were warm or cold and what the atmosphere was like.

Worksheet 9.1 and 9.2 9.2 Based on the Index fossil Chart, when was each rock formed? Rock A- Between 144 and 65 MYA (million years ago) Rock B- Between 206 and 144 MYA Why are index fossils useful for figuring out the age of disturbed rock layers? Index fossils can provide appropriate dates for each layer so they can help determine the original order of the rock layers.

Worksheet 9.1 and 9.2 9.2 2. Half-life % Uraanium 235 % Lead 207 100 1 100 1 50 2 25 75 3 12.5 87.5

Please take out your homework. Bell Ringer #16 Monday, April 10, 2017 Welcome Back. I hope you had a fabulous spring break! Carbon 14 has a half-life of approximately 5,700 years. Scientist discover a mammoth bone that has ¼ of its original carbon 14. How old is the bone? If only ¼ carbon 14 is left, then it has been through 2 half-lives. Sooooo… 2 x 5,700 = 11,400 years old. Questions and answers! Please take out your homework.

Unit 7 - Relative Dating and Fossils Chapter 9 – Views of Earth’s Past Section 9.3 – The geologic time scale shows Earth’s past

Time Scale Example Quarter Q1 Q2 Q3 Q4 Unit U1 U2 U3 U4 U5 U6 U7 Chapter C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 Section S1 S1 and S2 S1, S2 and S3 S1, S2, S3 and S4 S1, and S2

The geologic time scale shows Earth’s past Earth is Constantly Changing Who is James Hutton? The first scientist to present a hypothesis about the Earth changing over time. What is uniformitarianism? Earth is an always-changing place The same forces of change at work today were at work in the past

The geologic time scale shows Earth’s past The geologic time scale divides Earth’s history What is an eon? The largest unit of time on a geologic time scale What is an era? A smaller unit of time which eons are divided into What is a period? A smaller unit of time which an era is divided into What if an epoch? A smaller division of a era

The geologic time scale shows Earth’s past The geologic time scale divides Earth’s history What are the three eons of the Precambrian time? Hadean Archean Proterozoic What is the one eon since Precambrian time? Phanerozoic

The geologic time scale shows Earth’s past The Phanerozoic Eon Began around 544 MYA Three eras Paleozoic- ancient life Mesozoic- middle life Cenozoic- recent life

The geologic time scale shows Earth’s past The Paleozoic Era All life lived in the ocean Fish with backbones developed (Amphibians and) Reptiles, insects and ferns were next 248 MYA a mass extinction occurred ending the era

The geologic time scale shows Earth’s past The Mesozoic Era Dinosaurs ruled Mammals, birds and flowers appeared Lasted 183 MY Ended with another mass extinction possibly caused by one or more giant asteroids hitting the Earth.

The geologic time scale shows Earth’s past The Cenozoic Era Began 63 MYA Age of Mammals Divided into two periods Tertiary period Quaternary period The last 2 MY A series of ice ages Mammoths, saber-toothed cats and other giant mammals

The geologic time scale shows Earth’s past The Cenozoic Era The first HUMAN fossils are about 100,000 years old The end of the Quaternary period is defined by human C I V I L I Z A T I O N Homework Page 309 #1 - 4

Homework : Page 309 #1-4 1. Describe the concept of uniformitarianism. Forces of change on Earth today are the same as they were in the past. Example: Volcanoes erupt today just as they did in the past 2. What does the geologic time scale measure? It measures Earth’s history by dividing it into time intervals based on major changes

Homework : Page 309 #1-4 3. What was life like on Earth for most of its history? No plants or animals existed What period , era, and eon do you live in? Quaternary period Cenozoic era Phanerozoic eon

Turn it in at the end of the period Test Thursday Test Thursday IN CLASS ASSIGNMENT Turn it in at the end of the period Write out the questions and the answers Page 313 #1-16 #1-3 (just write the definitions) Test Thursday Test Thursday

Chapter Review 1. Index fossil Fossils of organisms that were common, that lived in many areas and that existed only during specific spans of time. 2. Ice Core Tubular sample of ice that shows how the layers have built up over time, Scientists observe trapped air and determine information about volcanic eruptions or how long an ice period or warm period lasted 3. Original remains Actual organism or soft part of an organism found where conditions prevent decomposition

Chapter Review 4. Which of the following might show evidence of a year with low rainfall? Tree rings 5. In which time span did dinosaurs live? b. Mesozoic 6. Half-life is a measurement of-----. b. Radioactive breakdown 7. What is the age of the Earth? c. 4.6 BYO 8. What was the earliest form of life? c. A one-celled organism

Chapter Review 9. Which statement best describes the concept of uniformitarianism? Earth continues to change just as it always has 10. How does petrified wood form? d. Water seeps through a log replacing its cells with munerals 11. A cast fossil is formed from-----. b. A mold 12. Which of these best preserves soft parts of an organism? c. Amber

Chapter Review 13. Which part of an ancient reptile would you expect to see in a rock fossil? b. Bone 14. Which type of fossil would be most likely to show the complete outline of a leaf? b. Carbon film 15. Why are no fossils found in igneous rock? Heat and pressure cause the material to breakdown and decay 16. Why is radioactive dating not useful for determining the age of sedimentary rock? Sedimentary rock is formed from many other rocks which may have varying ages

The half-life of carbon 14 is 5,700 years. How old is a rock that has only 6.25 % of the carbon 14 left? Half-life % cabon 14 100 1 50 2 25 3 12.5 4 6.25 4 x 5,700 = 22,800 years

Vocabulary Original Remains Mold Fossil Cast Fossil Petrified wood Carbon Films Trace Fossils Tree Rings Ice Core Relative Age Absolute Age

Short answer 1.What type of conditions would prevent decomposition? Ice, Amber or Tar 2.What do tree rings tell us? Width of a tree ring tells how much the tree grows in a year Thin rings suggests a dry year while a thick ring suggests a wet year 3.Why might ancient lakes and sea beds be rich sources of fossils? The hard parts of water organisms, such as shells, bones, and teeth drop to the bottom and get covered by sediment in layers over time.

Short answer 4.How do layers of sedimentary rock show age? Oldest layer at the bottom; youngest layer on top 5.Who is James Hutton? The first scientist to present a hypothesis about the Earth changing over time. 6.What is uniformitarianism? Earth is an always-changing place; the same forces of change at work today were at work in the past

Paleozoic- ancient life Mesozoic- middle life Cenozoic- recent life Short answer 7. What are the three eons of the Precambrian time? Hadean, Archean and Proterozoic 8. What is the one eon since Precambrian time? Phanerozoic 9. What are the three eras of the Phanerozoic eon and what are their meanings? Paleozoic- ancient life Mesozoic- middle life Cenozoic- recent life