Lesson 13: Oceanic Hotspots

During the next couple of weeks we'll be looking at parklands shaped by the processes that occur above mantle plumes or "hotspots". Most geologists now accept that such plumes rise from the deep mantle and have little direct connection to the processes that occur along plate boundaries. This view is supported by the fact that many hotspot volcanoes occur far from plate margins although a few, like Iceland, do lie along active boundaries. This week we'll visit the parklands of Hawaii to explore how volcanoes are built by oceanic hotspots and how the resulting islands change after volcanism ceases. Even though we'll be focusing on Hawai'i you should bear in mind that not all oceanic hotspots produce island chains that fit the "classic" Hawaiian model. Some, like the hotspot that built the Galápagos Islands on young, thin oceanic lithosphere, do not build linear island chains at all!

Because many of the islands produced by oceanic hotspots lie in the out in the open ocean they are subject to tsunamis triggered by distant earthquakes or massive submarine landslides. Our exercise this week will look at risks posed by these "seismic sea waves" as well as the "storm surges" that accompany powerful cyclonic storms.

As you read through this chapter and browse through the supporting websites please take careful notes so that you can keep track of major points and recall them more easily when we refer to them later in the semester. Be sure that you are prepared to meet the learning objectives outlined below before you move on to the quiz at the bottom of the page.

Weekly Learning Objectives

Upon successful completion of this week's lesson, a student is expected to be able to:

Reading and Browsing Assignment

Exercise 13 (Due by 9:00 AM on Monday, 19-Apr-2010)

Please load up your Hazard City CD, click on the Tsunami/Storm Surge exercise, and select version 3. Read through each of the introductory panels and then print the report and fill it out. Just a couple of pointers. First, in order to calculate the speed of the tsunamis in the "Tsunami Travel Time" question I simply laid a ruler against my computer monitor, estimated how may centimeters was equivalent to 2000 miles, and then measured to see how many hours each tsunami required to travel this distance. This is not a very sophisticated method but it works; also, remember, speed = distance/time. Second, in the questions about the town note that Ocean Village covers 20 blocks and the people are distributed evenly. This will make figuring how many people or buildings will be affected by a wave of a given run-up pretty easy. Be sure to have your final results in hand before you go to the Etudes "Assignments, Tasks and Tests" tool to complete Exercise 13.

Quiz 13 (Due by 9:00 AM on Monday, 19-Apr-2010)

After you feel you have mastered the learning outcomes outlined above, please complete Quiz 13 in the Etudes "Assignments, Tasks and Tests" tool. There are ten questions, each worth one point. If you can answer all of them correctly it means that you know your way around oceanic hotspots pretty well and are ready to move on to learn about parklands formed at continental hotspots next week.