Geology Exam

1. The 1883 eruption of Krakatoa in Indonesia caused several large tsunami that killed thousands of people.

True

False

2. Earth's climate is simply too stable to be influenced by large volcanic eruptions

True

False

3. Once a mass of magma is created, the magma's composition cannot be changed

True

False

4. __________ is the dominant rock type being erupted as lava flows at the crests of Earth's oceanic ridge systems, such as in the Atlantic Ocean east of North Carolina.

Granite

Pegmatite

Basalt

Quartz

5. The primary control on the style of volcanic eruption (quiet versus violent) is

Depth to the subduction zone

Height of the volcano

Magma viscosity

Magnetism

6. A stratovolcano

Sunset Crater, Arizona

Yellowstone, Wyoming

Shiprock, New Mexico

Mauna Loa, Hawaii

Mt. St. Helens, Washington

7. What does the term "pyroclastic" mean?

Any volcanic eruption of a non-silicate magma

Unusually fluid lava flows

High-quality obsidian used to make arrowheads and spear points

"fire broken" materials erupted by a volcano

8. What kind of volcanic material is erupted at the crest of a mid-ocean ridge?

Pillow lavas

Welded tuff

Andesite lava domes

Carbonatite hornitos

9. Extrusive igneous rocks are also called ___, while intrusive rocks are also called ___.

Plutonic, volcanic

Volcanic, plutonic

Plutonic, granite

Volcanic, basalt

10. ____ is the most dangerous type of volcanic activity.

Rhyolite pyroclastic flows

Basalt lava fountains

Basalt pahoehoe flows

Carbonatite hornitos

11. _____ is the primary "driving force" behind volcanic eruptions.

Magnetism

Temperature

Escaping volatiles (gasses)

Pluto, the Greek god of the underworld

12. A ______ is a volcanic mudflow that can be a very serious volcanic hazard.

Lahar

Fumarole

Caldera

Pahoehoe

13. Which of these is a common felsic igneous rock?

Quartz

Travertine

Basalt

Granite

14. Mt. St. Helens is a dormant volcano, which means that it

Will not erupt again

Is now classified as a sedimentary rock deposit

Can only erupt pyroclastic flows approximately once per million years

Will erupt again in the future

15. Most magma generated on earth

Stays below the surface and forms intrusions

Sings to the core-mantle boundary because of it's magnetism

Erupts at the surface and forms volcanic rocks

16. What is a fundamental difference in chemical compostion between the igneous rocks granite and basalt?

There is no difference

One rock contains abundant silicon and one rock contains none

One contains abundadant ferromagnesian minerals and the other has almost none

17. The largest masses of igneous intrusive rocks (plutons) exposed at Earth's surface are _________ composed of granite

Sills

Dikes

Laccoliths

Batholiths

18. Cinder cones are

Relatively small steep sided volcanoes

Typically composed of basalt

Built from ash, cinders, and other pyroclastic materials

All of the above

Only A and B

19. A cinder cone

Sunset Crater, Arizona

Yellowstone, Wyoming

Shiprock, New Mexico

Mauna Loa, Hawaii

Mt. St. Helens, Washington

20. How can hot rocks of Earth's mantle be caused to melt and create basaltic magma?

They can't- it is impossible to melt mantle rocks

Reduce the concentration of water and other volatiles

Reduce the confining pressure on the hot rocks

Reduce the temperature of the rocks

21. A shield volcano

Sunset Crater, Arizona

Yellowstone, Wyoming

Shiprock, New Mexico

Mauna Loa, Hawaii

Mt. St. Helens, Washington

22. A very large caldera

Sunset Crater, Arizona

Yellowstone, Wyoming

Shiprock, New Mexico

Mauna Loa, Hawaii

Mt. St. Helens, Washington

23. Gasses (volatiles) escaping from magma will produce vesicles (voids or bubbles) in the solified rock. Which of these is not an example of vesicular texture?

Scoria basalt

Rhyolite

Granite pegmatite

24. A ______ typically results from a major eruption of hundreds of cubic miles of hot ash.

Shield volcano

Cinder cone

Caldera

25. A dike is a type of igneous pluton that is _______ relative to the structure or layering of the older rocks that were intruded by the dike.

Convergent

Divergent

Concordant

Discordant

26. Much of the ______ Ocean basin is rimmed by active subduction zones, therefore it has most of Earth's ______ located around it's margins.

Pacific, shield volcanoes

Atlantic, shield volcanoes

Pacific, composite cones

Atlantic, composite cones

27. Which type of basalt lava flow is shown on the right side of the front projection screen?

Aa

Pahoehoe

Welded tuff

Quartz

28. A sample of Hawaiian basalt is shown on the left side of the front projection screen. Which of the following igneous textures is not displayed by this rock?

Vesicular (or scoria)

Phaneritic

Aphanitic

Porphyritic

29. The igneous plumbing of an extinct volcano

Sunset Crater, Arizona

Yellowstone, Wyoming

Shiprock, New Mexico

Mauna Loa, Hawaii

Mt. St. Helens, Washington