Class Discussion-Exam 2 Questions

The following are the final list of questions that the second exam will cover. Be sure to notice that the numbers are not the same as those at the end of the lecture notes. I will choose 5 of these and you will have to answer 4.

NOTE: The HINTS will NOT be included with the question on the test.

Magma Ascent and formation of Magma Chambers

  1. Describe the mechanics of Hawaiian shield volcanoes including ascent of magma from the mantle, summit storage, and rift zone intrusion. Discuss ideas related to density, driving pressures, petrologic evidence (magma chemistry), role of olivine settling, geodetic evidence (inflation-deflation) and seismic evidence.[hints: buouyancy and volume expansion in the mantle, the dense olivine core of the volcanoes].

  2. Explain the role of cooling of the magma and crystallization of olivine in producing the driving pressures necessary to inflate the summit magma chamber. How does this idea differ from the "neutral bouyancy theory" that the magma simply pools when it reaches a region of the volcano with density equal to that of the magma?

Eruption Processes

  1. Describe the 4 types of eruptions found on the Hawaiian islands and the mechanisms that produce them. List the primary eruptive products and the types of vent structures, as well as which stages these different eruption types might be expected to occur. Which produces the most dangerous eruptions? [hint: The types of eruptions are Hawaiian, Strombolian, hydromagmatic or Surtseyan, and Caldera Forming Hydromagmatic eruptions].

  2. Describe the 3 principle changes in eruptive style and vent morphology in a long-lived vent system on a Hawaiian shield-stage volcano. Why do these changes occur? [Hint: this question is asking about the progression from fissure to high fountain to continuous eruption].

Unstable Flanks and Eruption Mechanics

  1. Explain why Hawaiian volcanoes tend to have long linear shapes as opposed to more circular shapes. What are the "rift zones" found on Hawaiian volcanoes and why do they form? Why does Mauna Loa have "radial" vents on its NW side? [hint: Make sure you discuss stress fields and give examples of linear and ciruclar shields. Also the role the existing volcanoes play in shaping newer volcanoes.]

  2. How do the forcible injection and deep cumulate models differ in terms of their implications for eruptive mechanisms on Kilauea and relationships to the movement of the south flank. Describe how dikes should move in the forcible injection model and discuss how the behavior of the 1955 and 1960 eruptions in the lower rift zone supports or causes problems for this model. [hints: make sure that you discuss how the movement of the flank before and after 1975 effects the models and how it is related to summit magma pressure--overall deflation and inflation trends].

Giant Landslides and Slumps

  1. Describe and explain the mechanics of the Hilina slump. Why does it behave in this manner?

  2. What effect did the landslides on the Southwest side of Mauna Loa have on it's magma plumbing system? Are there any surface expressions of this event today?

  3. What are the two principal types of landslides on the Hawaiian Islands and what are likely causes of these differences? How do landslides help shape the islands and what effect might landslides have on calculations of lava production rates from the hotspot?