Bellringer As a group, write what type of fossil each letter represents. You may use your notes!

Fossils and Superposition Cornell Notes Key Terms Notes Summary:

Most fossils are formed in sedimentary rock. A fossil is the remaining part of a once-living thing that has been preserved in rock. Most fossils are formed in sedimentary rock.

How do fossils form? Organisms die Sediments are piled on top of slowly decaying organisms and hardens into sedimentary rock. Shells and bone take longer to decay.

HOT Question Can fossils form in Igneous and Metamorphic? Why or why not?

Fossils and The Law of Superposition

How do we know how old a fossil is? Fossils are clues in the story of Earth’s past! http://slideplayer.com/slide/9400608/

Relative Dating and Index Fossils Relative dating: Any method of determining whether an event or object is older or younger than other events or objects. Example: How many students in the class have an older sibling? Younger sibling? Index fossil: A fossil that is found in the rock layers of only one geologic age and is used to establish the age of the rock layers. Ex Trilobites

Index Fossils Squids Dinosaurs Trilobites Cats 1. What is an example of an index fossil? Squids Dinosaurs Trilobites Cats 2. If you uncovered a Bathyurus Extans, what time period would any fossil found around it be from? Triassic Period Ordovician Period Tertiary Period Paleozoic Era

Determining the ages of rocks using index fossils When using index fossils for relative dating, scientists study the position of the fossils in the sedimentary rock layers

Law of Superposition Fossils in lower layers of sedimentary rock are older than fossils that are in higher layers of sedimentary rock.

Laws of Relative Dating https://www.youtube.com/watch?v=M2Ex5DIjtfU

HOT Question! What is the age of an intrusion igneous rock in relation to the sedimentary rock layers through which it passes?

Index Fossils https://www.youtube.com/watch?v=V8zNrz_l108

Absolute Age & Radioactive Decay Absolute dating, using radioactive decay, gives us the actual age of the fossil Example: How old are your older brother(s) or sister(s)? Radioactive Decay: When atoms become unstable and breakdown and becomes a different element The half-life is the amount of time it takes for one-half of the original atoms to decay http://www.brainpop.com/science/earthsystem/carbondating/

How Does Carbon Dating Work? https://www.youtube.com/watch?v=Kcuz1JiMk9k

How do we know how old a fossil is? Relative Dating- uses index fossils to date sediment layers Absolute Dating- (numerical dating) uses radioactive dating

What have fossils told us about Mass Extinctions? https://www.youtube.com/watch?v=aO9mOAKXvJs&t=62s

Analyzing Fossils in Sedimentary Rock Homework Begin on homework Due tomorrow!

Activity # 1 On your desk, you have 8 large colored index cards with nonsense letters placed on them. Your task is to determine what the correct sequence of the letters are. You have two clues: The card with the letters “C” and “T” is on the bottom, or the oldest layer Look for a card that has either a “T” or “C” written on it for the second layer

M D X O MD N B DXO U A G ON C T NB NBU UA AGC C T This is one possible way to arrange the cards. Questions: What letter is the oldest? What letter is the youngest? What letter showed up the most? Which letters only showed up once? Which letters could be index fossils? How did you know which was older: “M” or “X”? MD DXO ON NB NBU UA AGC C T

M D X O N B DXO U A G ON C T NB NBU UA AGC C T This is one possible way to arrange the cards. Questions: What letter is the oldest? What letter is the youngest? What letter showed up the most? Which letters only showed up once? Which letters could be index fossils? How did you know which was older: “M” or “X”? DXO ON NB NBU UA AGC C T

Activity # 2 Flip your eight index cards over Arrange the index cards that represent layers of rock and fossils Clues: The oldest layer has the letter “M” in it Find a rock layer that has at least one of the fossils you found in the oldest rock layer Extinction is forever - once an organism disappears from the sequence it cannot reappear later

This is one possible way to arrange the cards. Questions: What fossil is the oldest? What fossil is the youngest? What fossil(s) could be used as index fossils? Which fossil existed in the most time periods? How can you tell when an organism has become extinct?

A N S W E R

To think about… What problems did you run into when trying to arrange the fossils into the correct sequence? Would this have been more difficult if you did not know which layer was the oldest to start the activity? Why? Which organism is the most complex of all the fossils and why?

Homework Superposition Worksheet

Bell Ringer What does the chart below display? What could geologist use this for?