OnlineOcean 101 - Hints for Lab #2

Some Hints for Lab #2 (Sea-Floor Spreading, Plate Tectonics, & Marine Geography)

ONLINE Oceanography 101 (Gwyneth Jones) - Bellevue Community College

Question #
Hint

Overall

* Feel free to post websites with good maps to the course discussion boards.

1

* Remember to be specific about the sub-type of convergent boundary.

* There can be two types of plate boundaries between two plates, at different locations where the two plates touch (if so, list both).

* Your options are (one or more of the following for each specific plate boundary location): divergent, transform, convergent-subduction, convergent-collisional.

2
* Remember, your options are "tension", "compression", and/or "shear". Which dominates at each of the specified types of plate boundaries?

3
* Be specific about which type of plate boundary, and explain your reasoning.

4
* See Figure 2-3 in the lab background information. Clearly and completely explain your reasoning.

5

* Purpose of this question -- To see that different mid-ocean ridges create new ocean crust at different rates (that is, they're spreading at different speeds).

* Equations you will need -- Distance = Rate x Time. In Figure 2-7 in your lab manual, you're given Distance (in kilometers) and Time (in millions of years), and you need to find Rate (in centimeters per year; "rate" means "speed" here). The equation can be rearranged to give: Rate = Distance / Time. Plug in the distances and times, then convert units to get final answers in cm/yr. See the lab manual for units-conversion equations...metric is lovely!

* Where do you get the data from? -- Notice that in Figure 2-7 there are 3 sets of squiggly lines and "bar-code" patterns: Top = S. Atlantic, middle = E. Pacific, bottom = Pacific-Antarctic. The very top row in the figure has the age scale (in millions of years) that applies to all 3 locations. "Zeroes" are at the crests of the ridges (as that is where new oceanic lithosphere is forming via seafloor spreading, as shown in Figure 2-4).

* I recommend you draw a vertical line at 60 or 70 million years (near the left side of the figure), and read off the data for each of the 3 sets of data. For each of the 3 locations, you're reading off the number of kilometers of new oceanic crust that has been created there in the past 60 or 70 million years (e.g.).

* Show all your work! Set it up neatly. Include units in every step. Show each step.

* Remember, plates move about 1-15 centimeters per year -- About the same speed that your fingernails grow! If you ended up with many kilometers per year, or only a tiny fraction of a centimeter per year, you'll need to recheck your calculations (you may just need to fix your unit-conversions...see the Lab #1 Hints).

6

* 6a & 6b relate to Q#5.

* 6c - See Figure 2-1 in the lab background information. Remember, Q#5 dealt with the Mid-Atlantic Ridge (MAR) south of the equator in the Atlantic; the East Pacific Rise (EPR) south of the equator in the Pacific; and the Pacific-Antarctic Ridge. Which two tectonic plates are between the MAR and the EPR, in the southern hemisphere? Those two plates are converging pretty much head-on...

7

* Similar sort of question as Q#5, but without the squiggly lines ;-)

* Recall that Distance = Rate x Time. This time, you're looking for Time, so rearrange that equation to Time = Distance / Rate.

* Answer should be in the millions of years.

8
* No calculations needed. Explain the processes, clearly and step by step. Your words should allow me to visualize it all.

9 & 10
* Remember, a hotspot stays stationary, and the tectonic plate moves over it.

11

* Describe your answer fully and clearly. Consider the reasons why these differences between active and passive continental margins exist.

12

* Name the specific location, where it is found, and how deep it is.

13

* Read the question carefully.

14

* Notice that each question asks for the physical or geographic relationship. How are these features related? Is there a plate-tectonic connection to explain the geographic relationship? Word your answers carefully.

15

* Iceland is in a very interesting plate-tectonic location. Look at the maps in your textbook that show Iceland (including Figures 3.10, 3.24, 3.25, 4.16, 4.17, and 4.26). See how Iceland is shown on each.

16

* Give specific examples. Word each answer clearly enough that I don't have to guess where you mean.

* Notice that the question asks you to "pick a different example location for each".

Question #	Hint
Overall	* Feel free to post websites with good maps to the course discussion boards.
1	* Remember to be specific about the sub-type of convergent boundary. * There can be two types of plate boundaries between two plates, at different locations where the two plates touch (if so, list both). * Your options are (one or more of the following for each specific plate boundary location): divergent, transform, convergent-subduction, convergent-collisional.
2	* Remember, your options are "tension", "compression", and/or "shear". Which dominates at each of the specified types of plate boundaries?
3	* Be specific about which type of plate boundary, and explain your reasoning.
4	* See Figure 2-3 in the lab background information. Clearly and completely explain your reasoning.
5	* Purpose of this question -- To see that different mid-ocean ridges create new ocean crust at different rates (that is, they're spreading at different speeds). * Equations you will need -- Distance = Rate x Time. In Figure 2-7 in your lab manual, you're given Distance (in kilometers) and Time (in millions of years), and you need to find Rate (in centimeters per year; "rate" means "speed" here). The equation can be rearranged to give: Rate = Distance / Time. Plug in the distances and times, then convert units to get final answers in cm/yr. See the lab manual for units-conversion equations...metric is lovely! * Where do you get the data from? -- Notice that in Figure 2-7 there are 3 sets of squiggly lines and "bar-code" patterns: Top = S. Atlantic, middle = E. Pacific, bottom = Pacific-Antarctic. The very top row in the figure has the age scale (in millions of years) that applies to all 3 locations. "Zeroes" are at the crests of the ridges (as that is where new oceanic lithosphere is forming via seafloor spreading, as shown in Figure 2-4). * I recommend you draw a vertical line at 60 or 70 million years (near the left side of the figure), and read off the data for each of the 3 sets of data. For each of the 3 locations, you're reading off the number of kilometers of new oceanic crust that has been created there in the past 60 or 70 million years (e.g.). * Show all your work! Set it up neatly. Include units in every step. Show each step. * Remember, plates move about 1-15 centimeters per year -- About the same speed that your fingernails grow! If you ended up with many kilometers per year, or only a tiny fraction of a centimeter per year, you'll need to recheck your calculations (you may just need to fix your unit-conversions...see the Lab #1 Hints).
6	* 6a & 6b relate to Q#5. * 6c - See Figure 2-1 in the lab background information. Remember, Q#5 dealt with the Mid-Atlantic Ridge (MAR) south of the equator in the Atlantic; the East Pacific Rise (EPR) south of the equator in the Pacific; and the Pacific-Antarctic Ridge. Which two tectonic plates are between the MAR and the EPR, in the southern hemisphere? Those two plates are converging pretty much head-on...
7	* Similar sort of question as Q#5, but without the squiggly lines ;-) * Recall that Distance = Rate x Time. This time, you're looking for Time, so rearrange that equation to Time = Distance / Rate. * Answer should be in the millions of years.
8	* No calculations needed. Explain the processes, clearly and step by step. Your words should allow me to visualize it all.
9 & 10	* Remember, a hotspot stays stationary, and the tectonic plate moves over it.
11	* Describe your answer fully and clearly. Consider the reasons why these differences between active and passive continental margins exist.
12	* Name the specific location, where it is found, and how deep it is.
13	* Read the question carefully.
14	* Notice that each question asks for the physical or geographic relationship. How are these features related? Is there a plate-tectonic connection to explain the geographic relationship? Word your answers carefully.
15	* Iceland is in a very interesting plate-tectonic location. Look at the maps in your textbook that show Iceland (including Figures 3.10, 3.24, 3.25, 4.16, 4.17, and 4.26). See how Iceland is shown on each.
16	* Give specific examples. Word each answer clearly enough that I don't have to guess where you mean. * Notice that the question asks you to "pick a different example location for each".