Class Discussion

Five of these questions will be on the test. You will need to answer 4 of them. Please give detailed answers using all of the availible facts that we have discussed in class and that are on the website. How you write is also important, please use full sentences and express coherent thoughts. Try to explain the answer as if you were telling a friend that doesn't know anything about the topic.

The parts of the questions in parentheses marked [Hint: ] will not be on the test question

PLATE TECTONICS STUDY QUESTIONS

  1. Draw and explain the simple structure of the Earth [Hint: Show the core, mantle, and crust and also the lithosphere]. Describe the three major types of plate boundaries and explain how convection of heat in the Earth's interior is thought to drive plate tectonics. Give some examples of how we know the plates are moving [Hint: Magnetic strips, age of seafloor, GPS measurements].

Island Chain

  1. What are the Hawaiian Ridge, the Hawaiian Deep, the Hawaiian Arch,and the Hawaiian Swell? How did they form and how are they related? Draw a section across (perpendicular to) the Hawaiian Ridge and label the ridge, deep, and arch.

  2. How do we know that the Hawaiian Islands are old? Give as many observations as you can to support this. [Hint: Things we discussed in class, coral reefs in various environment, age of ocean crust, spreading rates etc.] How do ages calculated by spreading rates compare to radiometric ages? [Hint: Compare spreading rates to the movements calculated using island ages]. How old is the crust underlying the Island of Hawaii? How old is the ocean crust beneath the oldest Emperor Seamount? What does this mean? [Hint: Discuss where the crust beneath Hawaii was formed and where the Hotspot was in relation to the ridge at both times].

  3. Give the rough age progession along the Hawaiian island chain, the NW Hawaiian Islands, and the Emperor Seamounts and explain why the younger islands generally increase in size towards the hotspot. [Hint: Give ages at the end of the chain, the bend, Midway Island, Kauai, Maui, the Big Island].

  4. Explain how we know that the Island of Hawaii is subsiding [Hint: compare reefs to tide guage data]. How does the rate of subsidence of Hawaii compare to Oahu? Explain the difference. [Hint: What is the process that causes the Big Island to subside?] What other process explains why the Hawaiian Islands above water and the Emperor seamounts below water? [Hint: the swell is warm].

HOT SPOT MODEL QUESTIONS

  1. Compare the Shallow Lithospheric fracture models of Hot Spot Formation to the Deep Plume Source models. Explain each model and how melting is generated [Hint: Decompressive vs Addition of Heat]. List the pros and cons of each model. Which model do you feel best fits the Hawaiian HotSpot. [Hint: All of the fracturing and shallow convection models along with the

PETROLOGY

  1. Describe and name the two principal chemical types of lavas found on the Hawaiian Islands. [Hint: Tholeiitic and Alkalic are the types]. How do differences in melting influence the type of lava produced? Explain the distribution of the 2 types of lava and how the amount of melting effects this distribution.
  2. Describe the isotopic evidence from the two types of Hawaiian basalt and MORB by comparing amounts of melting and closeness to the Earth's original composition. Use this evidence to explain where the sources are for the 2 types of Hawaiian basalts. What are the implications for Hotspot models?

Evolution of the Island Chain

  1. Describe the evolution of a typical volcanic edifice from its emergence on the sea floor through its stage as a submerged guyot. [Hint: List all of the stages and compare things like size, shape, eruptive style, eruptive frequency, onset of erosion, subsidence, etc.]

    If you have comments or suggestions, email me at kenhon@hawaii.edu