1. Section 3.1 Vocabulary to know: James Hutton Uniformitarianism
Catastrophism
Charles Lyell

2. James Hutton’s New Idea
Came up with a theory in 1788…
Uniformitarianism
Geologic processes happening today also happened in the past
Seems obvious, but actually sparked controversy

3. Catastrophism Vs Uniformitarianism
Not everyone liked Hutton’s ideas…
Catastrophism:
States that geologic change occurs suddenly
Uniformitarianism lost the debate until Charles Lyell proved Hutton to be right…kinda…

4. A Happy Medium
Most geologic processess follow Hutton’s theory of uniformitarianism…
But sometimes Catastrophism does occur
Asteroids
Meteor Crater in Arizona

5. Section 3.2 Vocabulary to know: Relative age Law of Superposition
Principle of horizontality
Principle of cross-cutting relations
Index fossil

6. What is their age?

7. ?????????? Don’t know their absolute age Relative age-
The age of an event or object (person) in relation to other events or objects (people)
In other words, you put things in order oldest to youngest…
…Or youngest to oldest

8. What can we learn about time from this picture?

9. You can learn a lot!
Until the 1900’s we couldn’t get absolute ages for fossils…
We had to assign things based on the order that they occurred
Law of Superposition-
Sedimentary rocks form in layers
Oldest layers on the bottom…
…Youngest on the top

10. Principle of original horizontality
Sedimentary layers are nearly horizontal when deposited…
Those that are not, have been deformed by movements of Earth’s crust

11. Principle of crosscutting relations
Geologic features, such as faults, and igneous intrusions are younger than the rocks they cut through

13. What’s the oldest layer?

14. Put these in order from oldest to youngest…
_____
Oldest

15. Index fossils Index fossil-
Fossils of organisms that were common, lived in many areas, and existed only during specific spans of time
Fossil found in specific rock layer MUST have lived during that time

16. Life cycle of a fossil…

17. Bad index fossils…Why?
Shark
Crocodile

18. Section 3.3 Vocabulary to know: Absolute age Atom Element Isotope
Atomic number
Atomic mass
Radioactivity
Half-life
Carbon-14 dating

19. Ok great… But how do we figure out the actual age of fossils?
Absolute age-
The actual age of an object or event
To figure out absolute age you have to take a look at atoms…
…more specifically, the isotopes of those elements made up of atoms
Absolute

20. A riddle to show me you understand…
There are two goat herders… One named Jeremy, and the other named Decker
Jeremy says to Decker, “Why don’t you give me one of your goats so that we have the same amount?”
Decker responds with, “No, why don’t you give me one of your goats so that I have twice as many as you?”
What is the relative amount of goats that each person has?
What is the absolute amount of goats that each person has?

21. Atoms Atom comes from the Greek word atomos… Atoms are made up of:
…which means: unable to cut
Atoms are made up of:
Protons (In the nucleus)
Neutrons (In the nucleus)
Electrons

22. Elements Element- Why is it 4.003, and not 4.0?
a pure substance that consists entirely of one type of atom
Make up everything in the universe
Atomic number-
number of protons.
Atomic mass-
protons + neutrons.
Why is it 4.003, and not 4.0?

23. Isotopes Isotopes are identified by their mass number.
Protons are constant…but sometimes there can be more neutrons than protons.

24. Radioactivity… Some isotopes are unstable
Meaning that they only exist for a little while before they change (Breakdown) into something else (more stable form)
Certain isotopes always change (Break down) into something else (more stable form) at the same rate

25. Use radioactivity as a geologic clock
Half-life-
Length of time it takes for half of the atoms in a sample of a radioactive element to change from an unstable form into another form
Different elements have different half-lives
Fractions of seconds
Billions of years
Parent
Daughter
Half-life (years)
Thorium-232
Lead-208
14 billion
Uranium- 238
Lead- 206
4.5 billion
Beryllium-10
Boron-10
1.52 million
Carbon-14
Nitrogen-14
5715

26. Half-lives
Rate of change from one element into another is measured in half-lives
Breaks down at a constant rate

27. Live organisms take in C14
Carbon-14 dating
Live organisms take in C14
Half-life = 5730 years
When an organism dies it no longer takes in C14
C14 breaks down into N14 at a constant rate
By measuring the half-life we can figure out when the organism died

28. Section 3.4 Vocabulary to know: Fossil Original remains
Ice (Original remains)
Amber (Original remains)
Tar (Original remains)
Sedimentary rock (Fossils)
Molds
Casts
Petrified wood
Carbon films
Trace fossils
Tree rings
Ice core

29. How do we know about the past?
Rocks and fossils!
Fossil-
Traces or remains of living things from long ago…
Fossils exist in many forms-
Hard animal remains (shells, bones, teeth, etc.)
Impressions on rock
And sometimes…

30. You actually find the organism
Original remains-
Fossils that are the actual bodies or body parts of organisms
Found in substances that keep out air and tiny organisms
Very important because they give DIRECT evidence that is undisputable

31. How are original remains preserved?
Ice-
Ice fields in Siberia and Alaska contain 10,000 year old mammoths and rhinos
Bones, muscle, skin, and even hair in place

32. How are original remains preserved?
Amber-
Tree sap traps insects within it
Tree gets buried and this sap turns into amber

33. How are original remains preserved?
Tar-
La Brea tar pits trapped animals from the past
Saber-toothed cats and other animals have been preserved

34. How do fossils form?
The organism must be preserved before it decomposes
Hard parts (bones, teeth, tree trunks, etc) decompose slowly
Soft parts (muscles, skin, etc) decompose fast
Most fossils are the hard parts of organisms

35. Where do rock fossils form?
Sedimentary rock-
Formed from sediments being compacted and cemented together
Sometimes the sediment builds up around plant or animal remains
If sedimentary rocks are changed by heat and pressure…
…the fossil is usually destroyed

36. Fossils in rocks Molds- Casts-
A visible shape that was left after an animal or plant became buried in sediment and then decayed away
Casts-
When a mold becomes filled with minerals and preserves the shape of the original organism

37. Fossils in rocks Petrified wood- Carbon films- Trace fossils-
Tree is covered in sediments…
…water with minerals seeps into the tree…
…minerals end up producing a “cast” of the tree
Carbon films-
Sometimes the Carbon from an organism is left behind as a visible layer
Trace fossils-
Not parts or an impression of an animal, but some other evidence
Ex: footprints

38. How do we know what the environment was like in the past?
Tree rings-
Width of the tree ring depends on how much the tree grew that year
Thin ring = dry year
Thick ring = wet year
Lot’s of growth during wet years
Ice cores-
Analyze air trapped within the ice to see how the atmosphere has changed
Can test ice from as far back as 530,000 yrs ago