fossils

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FOSSILS

+OCTOBER 9, 2012ScheduleCritique Your Thinking Essay Due FridayQuiz FridayLab Reports and Rock layer Models

TURN IN if you have not.Do your assignments some points are

better than NO points

+More recently deposited rock layers are more likely to contain fossils resembling existing species.

Fossils provide important evidence of how life and environmental conditions have changed.

“Fossils” can be compared to one another and to living organisms according to their similarities and differences.

Fossils can be used to help determine the relative age of rock layers are called index fossils.

+Fossils tell us…

1. Life forms have changed over timeExtinction of organisms is apparent in

the fossil record 2. Earth’s climate and surface have

changed over time.

+By studying fossils (and rocks)….Scientists have developed a geologic

time scale which outlines the major divisions of Earth’s history.

+How do fossils form?

Death Burial Sediments harden

+http://www.discoveringfossils.co.uk/whatisafossil.htm

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Geological forces distort the sediment

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http://www.discoveringfossils.co.uk/whatisafossil_stage_8.jpg

The uplifted rock is exposed to weathering and gradually erodes away

+http://www.discoveringfossils.co.uk/whatisafossil_stage_9.jpg

Roy Shepherd extracts the fossil fishhttp://www.discoveringfossils.co.uk/whatisafossil_stage_9.jpg

+Sept.19

Set up a paper for Cornell notesTopic: Types of FossilsEQ: Back board

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Turn in comics Notes Look at fossils

+Types of Fossils

+the different types of fossils based on how they were formedCarbonized fossil – forms when organisms or

parts, like leaves, stems, flowers, fish, are pressed between layers of soft mud or clay that hardens squeezing almost all the decaying organism away leaving the carbon imprint in the rock.

Trace fossil – forms when the mud or sand hardens to stone where a footprint, trail, or burrow of an organism was left behind.

Mold fossil – forms when sediments bury an organism and the sediments change into rock; the organism decays leaving a cavity in the shape of the organism.

+the different types of fossils based on how they were formedCast fossil – forms when a mold is filled with sand or mud that hardens into the shape of the organism.

Petrified fossil (permineralized fossil) – forms when minerals soak into the buried remains, replacing the remains, and changing them into rock.

Preserved fossil – forms when entire organisms or parts of organisms are prevented from decaying by being trapped in rock, ice, tar, or amber.

Unit 4 : Chapter 16 : Section 3

+Looking at Fossils

Fossil Amber with Insect Inclusions

•Fossilized tree sap is called amber

Unit 4 : Chapter 16 : Section 3

+Looking at Fossils

Fossil Amber with Insect Inclusions

•Animals caught in amber are perfectly preserved

Unit 4 : Chapter 16 : Section 3

+Looking at ICE

Woolly Mammoth

•Fossils of mammoths, extinct for 12,000 years, have been found frozen in Arctic ice

Unit 4 : Chapter 16 : Section 3

+Looking at Fossils

Theropod Track

•A trace fossil is naturally preserved evidence of animal activity

Unit 4 : Chapter 16 : Section 3

+Looking at Fossils

Theropod Track

•This dinosaur track is located in Glen Rose, Texas, in Dinosaur Valley State Park

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Mold fossil – forms when sediments bury an organism and the sediments change into rock; the organism decays leaving a cavity in the shape of the organism.

Unit 4 : Chapter 16 : Section 3

+Looking at Fossils

Ammonite Fossil

•A mold is a cavity in rock where a plant or animal was buried

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Cast fossil – forms when a mold is filled with sand or mud that hardens into the shape of the organism.

Unit 4 : Chapter 16 : Section 3

+Looking at Fossils

Ammonite Fossil

•A cast is an object made when sediment fills a mold and becomes rock

+Cast&Mold

http://www.salem.k12.va.us/staff/jwright/vocabulary/fossil_cast&mold.jpg

+Amber

+Imprint

http://www.salem.k12.va.us/staff/jwright/vocabulary/image2PV.JPGhttp://www.salem.k12.va.us/staff/jwright/vocabulary/image2PV.JPGhttp://www.salem.k12.va.us/staff/jwright/vocabulary/image2PV.JP

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+BILL NYE FOSSIL VIDEO

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Write the history of the place represented in the sedimentary column below. Be specific!

Warm-up: September 10, 2013

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Topic: Absolute DatingCarbon-14 & Uranium

+What is Absolute dating?

It is the age of a rock unit, fossil or geologic event expressed in units of time, such as years.

A good example is your birthday. You were born at a specific time on a specific day of the year.

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What is an example ofabsolute dating?

Carbon-14 dating is an example of __________(relative/absolute) dating.

+How does absolute (radioactive decay) work?

it will break down naturally into a lighter element called a decay product. This process occurs at a predictable rate and can be used to determine how old an object is.

Unit 4 : Chapter 16 : Section 2

+How does carbon-14 work?

•When animals eat, they ingest radioactive Carbon-14•organism grows, more Carbon 14 is added to it. •When the organism dies, the Carbon 14 starts to decay into Nitrogen 14 (stable element).

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Potassium

ROCK

1.3 billion years

(half-life)

Potassium

Argon

ROCK

+How fast do elements decay?

A certain element will decay at a constant speed. The speed never changes.

This rate of decay is known as the element’s HALF-LIFE.

HALF-LIFE = the time it takes for half of the radioactive element to decay into the new element.

+What is a Half-life?

A half-life is the time required for half of an element's atoms in a sample to change to the decay product.

In each half-life only half of the remaining radioactive atoms decay, no matter how large the sample is.

Unit 4 : Chapter 16 : Section 2

+What does a graph for radioactive decay look like?g

Exponential

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• Since C-14 has a half-life of only 5730 years, other isotopes are used to date older rocks

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Radioactive isotope Half-life time

Carbon-14 5.7 x 103

Potassium-40 1.3 x 109

Uranium-238 4.5 x109

Rubidium-87 4.9 x 109

+Easiest way to calculate half-life?

Chart the half-lives, radioactive element (or decay product) and the age of the sample are related.

+What is another method other than

C-14?Uranium (U-238) is used for

Radioactive dating in igneous and metamorphic rocks.

Uranium is a mildly radioactive substance that breaks down at a slow and steady pace which cannot be altered by temperature or pressure.

+How to calculate half life? Example. A piece of granite is determine to contain 50 grams of

U-238. After one half-life, how much material is left? After 2 half-lives? After 3 half-lives? After 4- lives?