1. GEOLOGY 117 -- THE OCEANS Get to web site from Illinois Compass
Instructor: Prof. Tom Johnson

2. Web Notes and Readings
One set of notes for each class; linked to class schedule on web page
Short reading assignments to be done before classes; listed in class schedule on web page
Get to the web page through Compass

3. What is Science? A collection of facts about nature?
-It’s much more than that
A process or method used to decide what is “true” and what is not?
-It is that, too.
A collection of ideas dreamed up by scientists that keeps changing and is never really reliable?.....

4. Science is often reliable.

5. How science progresses, succeeds, and fails:
We observe the world around us.
We try to make sense of it all. If we succeed at that, then maybe we can predict what will happen, or find a way to make something useful.
We make educated guesses- Hypotheses.
Some don’t hold up – useless.
Others do withstand the tests of time- useful!
So we test them- BIG TIME

6. How science progresses, succeeds, and fails:
Sometimes an idea becomes more than just an educated guess. After much testing, it really seems to work, and we call it a theory. Some theories are well established and reliable.

7. How science progresses, succeeds, and fails:
Sometimes an idea becomes more than just an educated guess. After much testing, it really seems to work, and we call it a theory. Some theories are well established and reliable.
Some theories are revised or overturned
- This does not mean that science is haphazard- it is part of the normal process
- We will examine the development of the theory of plate tectonics in this class. 

8. Subdivisions of ocean science: Marine geology Chemical oceanography
Physical oceanography
Biological oceanography
This is the basic order of topics in this course.

9. Class #2 -- Geology 117
The Earth, Part 1

10. The Oceans- Part 1 Marine Geology How did the Earth and Oceans form?
What does the ocean floor look like (shape)?
Why is it shaped that way?
Why does the earth have oceans and continents instead of just a single shallow ocean covering everything?
How do we “know” all this stuff anyway?
Do we really “know” or is it more “inference” than knowledge?

11. Latitude lines are “parallels”: constant distance between

12. Longitude (East-West)
Why measure longitude in degrees???

19. Continents mostly in the N hemisphere: Gives Earth a slight “pear” shape

20. When did the earth form and how did it form
When did the earth form and how did it form? How did it get to be what it is today?
About 5 B.Y. ago: Formation of the solar system Gravitational collapse, rotating disk… dust and gas (mostly H and He)
Then… accretion -- planets.
Earth, other planets, meteorites at ~ 4600 m.y.
Early molten(?) stage of Earth (first 200 m.y.):
- silicate mantle and metallic core formed

21. Layering of the Earth Based on Chemical Composition

25. Fig in Text

26. What is the evidence for this?
The way earthquake waves travel through
Each earthquake sends out waves
Thousands of seismographs detect these
e.g., Earthquake in Turkey, detected here
Two types of earthquake waves
compressional waves, or “P” waves
shear waves or “S” waves

27. P and S wave material not in textbook

30. P- waves (refraction, shadow zone)
S- waves (blocked by liquid, large shadow zone
Homogeneous earth would be like this:

31. Homogeneous earth would be like this:

33. P and S wave material not in textbook http://neic. usgs

34. P- waves (refraction, shadow zone)
S- waves (blocked by liquid, large shadow zone
Homogeneous earth would be like this:

35. More evidence used to infer what’s inside the earth...

38. More evidence used to infer what’s inside the earth...
Meteorites
Some are fragments of planets; broken apart billions of years ago
Some are Fe Metal
Some are Mg+Fe silicates like the earth’s mantle

39. How do we know when all this happened (“age dates”)?
Radioactive elements
Decay produces “daughter” products
Some radioactive elements have very long half-lives (e.g., Uranium)
Buildup of daughter products can be used to determine ages of rocks and meteorites

40. Represents amount of uranium
Represents amount of lead