Olympus Mons and Hawaii

Olympus Mons and Hawaii

Our investigation this week focuses on the following question: if the Pacific Plate were stationary, which would be bigger, Hawaii or Olympus Mons? Olympus Mons is the largest volcano in the solar system. With a base the size of Ohio, it is a whopper of a volcano! So how can we compare Hawaii to that?

The Hawaiian Islands have formed over an oceanic hotspot in the middle of the Pacific Ocean. But that’s not all. There is a whole string of volcanoes, mostly underwater now, from Hawaii to the northern Pacific Ocean. They are called the Hawaiian Island – Emperor Seamount chain. It is a string of volcanoes, rather than a single volcano, simply because the Pacific Plate is moving. If the Pacific Plate were stationary, the magma (lava) from the Hawaiian hotspot would have all erupted in one place. Because the plate moves over the source of that magma, the hotspot has left a trail of volcanoes on the Pacific Plate.

Let’s imagine what Hawaii would be like if the Pacific Plate were stationary. It would include all of the rocks formed from the magma that has come out of the Hawaiian hotspot, past and present. It would, in fact, be a lot like Olympus Mons: a huge volcano. My question for you is, how huge would it be?

Part 1:

So. What about Olympus Mons? How big is it? WHERE is it?

Olympus Mons is on Mars. I had hoped that I’d be able to see it through the telescope at our observatory this fall, but I was sadly mistaken. (Nonetheless, it’s fun to see the polar icecap.) Anyway…. Since we are using it as a basis for comparison, our next task is to answer the question “how big IS Olympus Mons?”

Use the digital photograph of Olympus Mons to measure its radius (distance from the center to the edge). Of course, the radius varies depending which direction you measure. Measure the radius where it seems to be about average. You will have to convert your measured distance to the actual distance using the map scale. What is the radius of Olympus Mons?

Check that answer. If you double that distance, is it about equal to the distance across Ohio? (Remember that 100 km is just over 60 miles.)

Okay, so it’s big around. How high is Olympus Mons? Let’s go out in the hall to see the digital map of Mars and find out.

How much higher is it than Mount Everest? Think about that…. Can you picture a volcano as big at the base as Ohio, and that much taller than Everest?

Finally, we want to know how much lava was erupted to form Olympus Mons. To figure that out, what’s the best measure of the size of Olympus Mons? Talk about it in your groups; then we’ll decide as a class, and go from there.

Part 2: Well, what about Hawaii? How big would it be, if all of the magma from the Hawaiian hotspot had erupted in one place, instead of forming a chain of volcanoes? Take a few minutes to brainstorm how we might figure that out. When the class suggests a method that would work, I will share with you the data that have been collected to answer this question.

Part 3: Compare. Which would be bigger? Then, think about this. The Hawaiian Island – Emperor Seamount chain goes all the way to the subduction zone near the end of the Aleutian arc. It’s possible that older seamounts in the chain have already been subducted. If that were the case, would it change your answer to the question above? Why or why not?

For your report, due next lab period:

Grade / Criteria
Outstanding / Meets the criteria for “Exceeds expectations,” and goes beyond: if Olympus Mons is found to be bigger, calculates when the Hawaiian hotspot will have erupted a volume of lava equal to Olympus Mons; if the Hawaiian chain is found to be bigger, calculates when it surpassed Olympus Mons in volume. Explains how that calculation was done. Goes beyond grammatical correctness to real readability.
Exceeds expectations / Meets the criteria for “Acceptable,” and includes explanations of how a hotspot track forms and of how subduction at the northern end of the chain affects the volume calculation for Hawaii. Any errors or omissions are minor. Excellent organization, good grammar, & very few spelling errors.
Acceptable / Includes: (a) a statement of the question being investigated, (b) radius, height, and volume of Olympus Mons, along with an explanation of how you calculated volume, (c) volume of the Hawaiian Island – Emperor Seamount chain, along with an explanation of how it was calculated, and (d) an answer to the question of which would be bigger. Explanations are reasonably accurate and organized. Calculations use significant figures. Calculations need not be typed, but the remainder of the report should be.
Poor / Not up to snuff. Report is incomplete, or inaccurate, or is not typed. Disorganized; awkward sentence structure; poor grammar &/or spelling.
Dreadful / Doesn’t effectively address the assignment. Report is grossly inaccurate or incomplete. Disorganized; awkward sentence structure; poor grammar &/or spelling.
No credit / Does not address the assignment, or uses outside references and fails to cite them properly.

Pro Tip: In your report for this lab, as well as several subsequent labs, you will find yourself reporting numbers and units with exponents. For example, your volumes will be in cubic kilometers. You can write that out, but it is often more practical to use exponents: km3. Here’s how to do that, in Microsoft Word: First, type out whatever it is, without worrying about superscripts: km3. Then, select the portion that you want to make into an exponent (in this case, the digit “3”). Then go to the “format” menu and select “font.” An array of choices pops up. In the “effects” box, select “superscript,” then click “ok.” And there you go; your “3” will have become an exponent. Now, for your reports for me, you have two choices: write in all of your exponents by hand, or use the superscript feature in your word processor. No “km^3,” please!!