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RAP 3/14 pg. 42. How old is the Earth? How do we know?. TOPIC: Geologic History. 29.1 Fossils 29.2 Relative Time 29.3 Absolute Time. Paleontology. The study of life that existed in prehistoric times. I. Fossils . -Preserved remains or traces of once living organisms. A. Types.
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RAP 3/14 pg. 42 How old is the Earth? How do we know?
TOPIC: Geologic History 29.1 Fossils 29.2 Relative Time 29.3 Absolute Time
Paleontology • The study of life that existed in prehistoric times
I. Fossils -Preserved remains or traces of once living organisms
A. Types 1. Original Remains -preserved in its entirety Ex: Wooly mammoths in ice and soil Insect in amber
2. Replaced remains -Soft parts replaced by minerals Ex: Petrified wood
3. Molds and Casts -Mold: hollow depression (cupcake pan) -Cast: copy of original fossil (cupcake)
4. Trace -indirect evidence of life Ex: trails footprints burrows bite marks
Trace fossils And one more example... coprolite
-thin carbon film 5. Carbonaceous Remains Ex. Fern print
Fossil Formation Fossil formed? Type Why/Why not? 1 No not deep enough 2 Yes Original Remains frozen 3 No too deep 4 No too much pressure 5 Yes replaced remains fused with minerals 6 Yes mould cast minerals filled in 7 Yes trace uplifted
Fossil Formation • Burying Bodies • Making Fossils
RAP 3/15 pg. 42 • What type of rock do most fossils occur in? • What is one method of preserving a fossil? B A 3. In the picture, which letter represents the mold? Which letter represents the cast?
II. Relative Time- placing events in the sequence in which they occurred **Does not identify actual ** dates
A. Principle of Uniform Processes 1. processes that occurred in past produce same results as today
B. Principle of Superposition • Deposited sediments are compressed into layers, or strata 1. Oldest layer at ; youngest at bottom top
Who Dunnit?! Someone took the last cookie in the cookie jar last night. The last person to leave is the culprit! Clues: • The Butler walks to work • The Handyman rides a bike • The Cook rides a motorcycle • The Maid drives a car • The Nephew has a seeing-eye dog
Sequences on pg. 44 3 2 1
4 1 2 3
C. Principle of Cross-Cutting Relationships 1. intrusion is always than rock it intrudes Igneous younger
4 2 1 3 5
Gaps in Relative Time D. Unconformity 1. indicates where layers of rock are missing a. Exist because -Lack of deposition -Erosion Example
E. Index Fossils 1. Four characteristics a. Easily recognizable b. Abundant c. Widespread in occurrence d. Existed only for a brief period
Who’s On First?: Period 6 Groups Lab Table 4 Mitchell Devin Jordan C. Kaitlin Bennett Lab Table 5 Davon Ashtyn Trey Lab Table 6 Josue Yony Ben Luke With Ms. Renwick Group 7 Chrissy Kaitlyn Bishop Dylan Wimer Anandhu Group 8 Zach Robert Jordan B. Lab Table 1 Shannon Jake Jenny Lab Table 2 Chase Brice Lab Table 3 Alex Daniel Dylan S.
Put it all together... • Decoding geologic history... • And…
B RAP 3/19 pg. 42 C A 2. Put the following events in the correct order. 1. Select the fossil you think would be the best index fossil and explain why. D
F. Correlation 1. Matching of rock layers from one area to another
Practice! unconformity Section 1 Section 2
What is the sequence of rock layer from oldest to youngest? An unconformity (buried erosional surface) is represented by the interface between which two layers? Of layers E and F, which is oldest? Which layers are the same?
III. Absolute Time A. Use ACTUAL dates to order events
B. Methods 1. Tree rings 2. Varves- layer of sediment representing summer and winter
RAP 3/20 pg. 46 • What is the difference between relative and absolute time? • What type of fossil shows evidence of an organism but not the organism itself?
RAP 3/21 pg. 46**QUIZ ON FOSSILS, Relative and Absolute Time • What is the relative age of layer C and D? • What two things can cause an unconformity? • Which letter to the right represents an unconformity?
3. Radiometric dating Pb Compares ratio of naturally occurring unstable isotope (parent) and its decay products (daughter) Ur
Parent = original element • Daughter = the product of the decay • Example: uranium-238 decays to lead-206
i. Half-life -Time it takes for half the radioactive atoms to decay =1 half-life =2 half-lives
In each half-life, the amount of atoms gets cut in half. =parent =daughter
One half-life. =parent =daughter
Two half-lives. =parent =daughter