Geologic Mapping C Question Marathon

[Pupitre]

Good news: Someone else answered a geomaps question!
Bad news: It was syo_astro...not exactly a new face in Geologic Mapping

Do you mind telling me how you figured out the intrado/extrado question? I want to see if we have the same thought process.

Well to be completely honest, my thought process was closer in nature to a guess I figured since it's width increases to the left, you'd be most likely seeing the interior of the fold, if that makes sense. I mean those terms are pretty obscure. After I submitted my answer I googled 'em and barely found anything in english.

[elephantower]

Well that's pretty much what I was thinking . And pigeon yeah intrado is obscure, that's why I put it there! Can you tell me what type of fold it is?

Also, I went back and assigned point values based on difficulty and number of parts for all the questions. Thus, your score on the amazing elephantower test (and it+some other questions is a 50-minute test in the exchange now, if you want to try it under time constraints) is:
26/41= 63%

[Pupitre]

Well that's pretty much what I was thinking . And pigeon yeah intrado is obscure, that's why I put it there! Can you tell me what type of fold it is?

Also, I went back and assigned point values based on difficulty and number of parts for all the questions. Thus, your score on the amazing elephantower test (and it+some other questions is a 50-minute test in the exchange now, if you want to try it under time constraints) is:
26/41= 63%

Cool, I'll give it a shot Time always flies during these tests. Jeez T-6 days is kinda freaking me out now haha.

[elephantower]

Next 2 questions cuz why not:
1. Identify this fold:

2. A concentric antiform with an amplitude of bluntness of 1 and an axial plane with an attitude of S65W has been eroded on level terrain such that the topmost sedimentary layer is completely eroded at the hinge line (and only there), revealing the layer below (the beds have equal thickness). A borehole of length 1000 m has been drilled from one inflection point to the other, passing through three distinct layers and the hingepoint of a fourth. A road crosses the fold from east to west. What is the total distance the road travels along the topmost layer of that antiform?

There's a chance that that second one isn't solvable, but I think it is (I'm working on it right now)
Also, I think you owe me a few questions haha

PS It's freaking me out too...you can tell by my obsessive question posting!

[Pupitre]

Next 2 questions cuz why not:
1. Identify this fold:

2.A concentric antiform with a bluntness of 1 and an axial plane with an attitude of S65W has been eroded on level terrain such that the topmost sedimentary layer is completely eroded at the hinge line (and only there), revealing the layer below. A borehole of length 1000 m has been drilled from one inflection point to the other, passing through three distinct layers and the hingepoint of a fourth. A road crosses the fold from east to west. What is the total distance the road travels along the topmost layer of that antiform?

Also, I think you owe me a few questions haha

PS It's freaking me out too...you can tell by my obsessive question posting!

Yeah I know I have to give you a few.

1. That looks like an eroded dome to me, unless I'm missing something super obvious.
2. If I'm doing that right, a bluntness of 1 would mean the fold is isoclinal? I know generally the type of triangle that needs to be set up but I'm not sure how to gather information from the borehole orientation. Would you mind explaining?

[elephantower]

Nope, not a dome--for one thing domes are usually map-scale, not specimen-scale. It's a type of fold.
For the second one, I'm not even sure it's solvable--I'm working on it now. However, a bluntness of 1 means it's circular, not isoclinal (isoclinality is related to tightness, not bluntness).

[Pupitre]

Good news: Someone else answered a geomaps question!
Bad news: It was syo_astro...not exactly a new face in Geologic Mapping

Pupitre, you read a random article and came up with a tangentially related question? You wanna play that way? OK then:

Describe the relationship between cooling speed and columnar jointing shape in igneous lava flows. If you get that question without using google, I will personally bow down to you at nats...

So do you want me to tell you the other answers? Also, do you mind telling me how you figured out the intrado/extrado question? I want to see if we have the same thought process (and I'm a bit suspicious after your guessing comment).

Oh I missed this one. Well if you're looking for a formula, I'm sorry I'm at a loss. But columnar jointing, let me say, is probably one of the most badass rock formations to ever come into existence. Isn't cooling speed inversely proportional to the size of the columns created? At least that's what seems to make sense to me.

EDIT: Haha I had a feeling I was wrong in the first one. Now to consult my binder. Don't have that exact picture but my best guess is a sheath fold?

[elephantower]

Giant's causeway! Basically, fast-cooling flows joint pentagonally, and slow-cooling ones hexagonally. Also, yes, a sheath fold.

[Pupitre]

Giant's causeway! Basically, fast-cooling flows joint pentagonally, and slow-cooling ones hexagonally. Also, yes, a sheath fold.

Oh phooey...

1. What is a nappe and what are two landforms that can be created by nappe movement? Explain how each one is formed.

2. Relative to the hinge, what is the direction of slip in flexural-slip folding?

[elephantower]

That second question is solvable, and I just solved it

Here's how (Click to Show Hidden Text)

First, note that the bluntness=1. This means that it is a circular fold. Because it is concentric, the layers all have the same thickness. The borehole at the inflection points cuts along the diameter of the circle. Because there are 3 layers on each side of the axial plane, there are 6 layers cut overall. Thus, the thickness of each layer is 1000/6. Now, we need to find the chord formed by the intersection of the surface with the circle. To do this, use the formula for a chord 2*(r^2-d^2)^.5, where r is the radius of the circle and d is the perpendicular distance from the chord to the center. D is 2*1000/6=1000/3, and r is 1000/2=500. Then, to find the distance of the road, we use the formula sec(a)*c, where a is the angle between the line perpendicular to the exposed surface and the road, and c is the chord length. The answer is 1763.66 meters.

Your questions:

... (Click to Show Hidden Text)

1. Klippes and fensters? Low ridges? I'm not sure.
2. Awesome question: If the hinge is N then the slip is NE on the right side and NW on the left side of the axis.