Astronomy quiz question: Mars' shield volcanoes

Astronomy 210 Quiz 7, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] Shield volcanoes on Mars appear to be caused by:
(A) oceans, when it was younger.
(B) runaway greenhouse effect.
(C) heavy bombardment.
(D) vertical motion of magma under the crust.

Section 70158
(A) : 7 students
(B) : 8 students
(C) : 3 students
(D) : 33 students

Correct answer: (D)

Magma flowing up through hot spots in the thick, static crust of Mars have built up large shield volcanoes on Mars.

"Difficulty level": 74% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.62