Ch 4 History of a Habitable Planet Dodos Dinos and Deinococcus Questions

CHAPTER 4 Questions

1) Our understanding of all history, but particularly deep-time geologic history, is dominated by the ideas of cycle and event. Even in our own lives there are things that click along in uniform fashion; and there are things that represent truly unique events.

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A) Think of some things that you did today and that you also did yesterday and even the day before. Make a list of at least 4 different things that you do every day.

B) Most likely, there a number of things that you did today that you did NOT do at all during the last week? Give a couple examples of such “unique” things.

2) What is uniformitarianism?

3) What is catastrophism?

4) How can you link the discussion of things that you do every day (or don’t usually do) to the concepts of uniformitarianism and catastrophism?

5) No cheating now! No doing any “research.” No asking your parent, roommate, spouse, friend, etc.!!

It’s perfectly OK if you have to write “I don’t remember.”—-

What did you have for dinner last night? ______
The night before last?_________
Three nights ago?_________
Four nights ago?__________
How about two weeks ago from last Wednesday? ___________

If you can answer all of these, then you are quite unusual. Most people cannot. One of the reasons that we can’t recall such things is that our memory of our past is “fragmentary”. In fact, this is the nature of all historical information. The further we go back, the less information exists.

Wouldn’t it be nice if we had a perfect “movie-like” record of all past events, going back into the depths of geologic time. Unfortunately, just like the depths of your last week’s dinners, we don’t.

6) Lord Kelvin was a sharp guy…. As a matter of fact, he earned his PhD at age 19, and was a full professor around age 21. But, he was ultimately wrong about the earth being no more than a few tens of millions of years old. In fact, the earth is many hundreds of millions of years old. Kelvin’s calculations, based on earth cooling, did not take into account what important factor?

7) Isotopic dating—remember, as the parent decays, the daughter increases. As a matter of fact, all of the parent that decays becomes daughter. Example: Let’s say a parent abundance decays from ¼ to 1/8; this marks a reduction of 1/8, so the daughter abundance increases by 1/8. Now you should be able to finish the table below by putting numbers into the spots marked by question marks.





















8) Now, using the above table, you should be able to determine how many half-lives have transpired to yield a 7:1 ratio of Daughter/Parent.

Number of half-lives transpired to generate 7:1 ratio = ___________

If this 7:1 ratio was found for the K-Ar system, what would the rock age be?

(FYI– You’ll need to look up the half-life of K-40)

9) What kinds of rocks are best suited for isotopic dating—igneous, metamorphic, or sedimentary? Explain why.

CHAPTER 5: Assignment

1) List the three different types of “unconformities” described in your text.

And, which of these do you think would be the most difficult to discern when out looking at rocks in the field?

2) Read the section on Marine Transgressions and Regressions and look carefully at Figure 5.9.

Let’s say that you find some lake deposits, at a particular location, with the following vertical sequence—

Top Layer — stream and delta deposits.
Middle Layer — fine grained siltstones.
Bottom Layer — mudrocks.

What type of lake level change occurred here to make this sequence?
(In other words, did the lake get deeper or shallower over time?)

3) What are the two types of stratigraphic correlation given in your text?

Which of these relies heavily on guide fossils?

4) What exactly is a guide (or sometimes called “index”) fossil?

5) Go on-line and pick an interesting fossil deposit–anywhere in the U.S. or in the world.

Provide—Name of Locality, Type of Fossils Present, and Age of Deposits.

6) The boundary between the Silurian and the Devonian is 408 million years ago.

Doesn’t that seem like a silly number! Most time boundaries on the geologic time chart are NOT round numbers that might be easy to remember!

These numbers refer to marked changes in something.

What sort of “changes” do these time boundaries refer to?

CHAPTER 6: Questions

1) Looming above the University of Colorado, southwest of Boulder, are the large tilted rock slabs known as “Flatirons.” If one walks up and looks at these rocks, one sees alternating layers of mudstone, sandstone, and conglomerate. The conglomerate contains “clasts” (i.e. individual pieces) that are partially rounded. These deposits are very similar to what we might find in river and stream systems on the edge of a modern active mountain range, where sediment is rapidly accumulating out in front of the range.

Based on the above paragraph, we interpret the Flatirons as evidence of an ancient mountain range that existed during the Late Paleozoic. Eventually we’ll learn about how they were tilted during Late Mesozoic and Early Cenozoic mountain building.

When we use modern environments to interpret the environments of the past what key principle are we invoking, from Chapter 4??

2) Flatiron rock (technically referred to as the Fountain Formation) is a variety of shale, sandstone and conglomerate known as “arkose.” What is an arkose and what does it tell us about the origin of the Flatirons?

3) Sediment becomes sedimentary rock through a process that involves compaction, dewatering, and cementation; often referred to as lithification. You should be familiar with this process.

Now, here’s a tough question: Do you think that all sediments become sedimentary rocks? Explain, why or why not?

4) In the first paragraph of chapter 6, the authors use the terms—detrital and chemical sedimentary rocks. What do these terms mean?

5) Make sure that you first look up what is meant by the term “depositional environment.”
Describe a reasonable “depositional environment” for the following sedimentary rock types.

a. well-sorted and very fine grained detrital sandstone

b. limestone

c. sandstone with large-scale and hi-angle cross bedding

CHAPTER 7: Assignment

Here is a good web site that might be worth examining along with the reading of your chapter. (Links to an external site.)Links to an external site.

1) In chapter 5, you were introduced to the principle of faunal succession. This is sometimes referred to as the “fact” of evolution as opposed to the “theory” of evolution. What do you think distinguishes the principle of faunal succession from the theory of organic evolution.

2) The elements of Darwinian evolution theory—natural selection—are quite simple, requiring three principles:

1= Variation of traits within a species and
2= The capacity to pass on useful traits to offspring (more or less “undiluted”),
3, one other basic “principle of existence”.
What is this other principle? Explain…

3) Recall the questions from Chapter 4.
You most likely were able to remember what you had for dinner last night.
Two nights ago? Perhaps
But, what about 3 weeks ago, Tuesday? Most likely not.

This seems to indicate that since there are missing “dinners” from the repository of your memory, perhaps you didn’t eat dinner on those evenings.

A common criticism of organic evolution is the lack of “intermediate forms” in the fossil record. Should we consider their absence to be evidence of their never having existed? Explain.