What is the difference between an earthquake “epicenter” and an earthquake
1) Go visit
http://neic.usgs.gov/
(and/or other suitable web sites that detail recent earthquakes)
Find info on a recent earthquake, greater than magnitude 5.
Now, describe the following…
A) Where did it occur? B) When did it occur? C) Magnitude and Effects? D)
Tectonic setting? (Tectonic setting= type of plate boundary, or intra-plate.)
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!
How do the wave-heights (“amplitude”) AND wave velocities of typical tsunami
compare to wind-generated waves?
4) Why is carbon dating (utilization of C-14 to C-12) technique not very useful for
rocks, or for any materials older than a couple hundred thousand years?
5) Let’s say that I grind up a detrital sedimentary rock and put it into a “radiometric
dating machine.” Is the date that I obtain very useful?
(Two hints: Under “uses of isotopic dating” your textbook states that “sedimentary
rocks are difficult to date reliably”—why? AND—Think about what detrital
sedimentary rocks are composed of.)
6) OK, let’s say that you want to figure out how old a sedimentary rock 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. Please define what we mean by “INDEX
FOSSILS” are AND explain how they are used in determining sedimentary rock
ages.
7) Let’s say that one meter (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) is probably
the most difficult to recognize when looking at a cross-section of rock out in the
field?
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.