Covers chapters 7 and 8

Earthquakes
Time and Geology

View:
Geologic Time Lecture

San Andreas Fault Elastic Rebound Theory

Rocky Mountain Uplift Lectures

Note: Answers to “short-answer” questions should be no longer than a few sentences.

1) First, watch the SA Fault Elastic Rebound Theory Video…and then answer the following questions:

What sort of fault is the San Andreas?—
A. Normal Fault
B. Reverse Fault
C. Strike Slip LEFT LATERAL (transform) Fault
D. Strike Slip RIGHT LATERAL (transform) Fault

Next,

Go visit https://earthquake.usgs.gov/earthquakes/ (Links to an external site.)Links to an external site.

(Links to an external site.)Links to an external site.(or another suitable web site that details recent earthquakes)

Find info on a recent earthquake, greater than magnitude 5.
For the earthquake,
ANSWER the following…

A) Where did it occur?
B) When did it occur?
C) Quake Magnitude and Effects (damage, life loss?)
D) Tectonic setting? — in other words… Convergence (subduction)? Transform (strike slip faulting along plate boundary)? Intraplate (not really on a plate boundary)?…. This is the key question for points,, so review your information website, or consult a “tectonic map” to get an answer!

2) What is the difference between an earthquake “epicenter” and an earthquake “focus”?

3) Waves in the ocean are generally made by wind. Tsunami are different!

A) What happens to a tsunami wave as it approaches shore– does it INCREASE in wave height or DECREASE in wave height?
B) How fast do tsunami waves typically move, in the open ocean?

4) Carbon dating does NOT work well with rocks (or with anything particularly old, in a geological sense!.)
Why is the Carbon Dating technique (utilizing C-14 to C-12 decay) limited to use with things that were once alive?

5) DETRITAL sedimentary rocks are difficult to date. (Review definition of this type of sedimentary rock.)

A– Why is an isotopic (i.e. radiometric) date, using radioactive parent-daughter pairs, not very useful for a detrital sedimentary rock?

AND (most important part of question, for most points)
B– Would the isotopic age obtained most likely be younger or older than the true age of the sedimentary rock?

6) OK, let’s say that you want to figure out how old a sedimentary rock actually is!
One way would be to look at igneous layers either above or below (or cross cutting dikes). Another way would be to use Index Fossils.
Define what we mean by “INDEX FOSSILS” and explain how they are used in determining sedimentary rock ages.

7) Let’s say that one meter (i.e. 100 cm) represents a time-line for the entire 4.5 billion year span of earth history.
How far along the meter stick would one find the boundary between the “Precambrian” and the “Phanerozoic”?

8) Review the section in your Earthquake chapter titled “Subduction Angle.” Now consider this question:
When the Rocky Mountain rose, starting about 70 my ago, subduction of the Farallon oceanic plate beneath North America involved a high rate of subduction and a mid-ocean ridge that was close to the subduction trench. This is further detailed in the video—Rocky Mountain Uplift Part 2
Recognizing that this proximity of the newly formed ocean crust to the subduction trench means that the descending plate was relatively warm….decide whether or not the subduction angle at that time would have been steep or shallow. Please explain your reasoning.

9) Unconformities are challenging for geologists. They are like missing pages in the book of earth history, which we are trying to read! Please review sections on unconformities in your text.
Which type of unconformity (angular, nonconformity, or disconformity) involves original sedimentary layers that have been deformed (tilted), then eroded, and then covered by subsequent horizontal sedimentary layers?

10) Assume that you have 100 pounds of radioactive Lesterium (a radioactive element named after me…sorry, you won’t find it in the periodic table!). It has the convenient half life of ONE year.
Based on the concept of half-life, after one year you’ll have 50 pounds are left.
After two years, you’ll have 25 pounds left.

Will a time come when there is absolutely zero left? Yes, No? Explain.

BEFORE TAKING EXAM 1—you should review all chapters covered up to this point.
Visit the link titled — How to Get Ready for An Exam

You should review the material under the chapter-by-chapter study guide.

You should review your returned assignments, using them as launch points for further study.

You should review all referenced videos and animations.

You should review the Module 1 and Module 2 Review Power Points.

You should take the SELF-TESTS covering assignments 1-4.

And, you should email me if you have any questions regarding terms or concepts.