Quiz #19

13 October 2011

S.I. Session 19 Quiz

This quiz covers material from the lecture on Wednesday, October 12^th.

Part a) Match the term to its definition:

                TERMS:

a)Andesite                          b)Magma Chamber                         c)Pahoehoe

d)Rhyolite                           e)Basalt                                                                f)Lava

g)Rhyolitic                           h)Basaltic                                             i)Aa

x)Obsidian                          y)Pyroclast                                          z)Pillow Basalts

                DEFINITIONS:

1)__This part of a volcano is typically only 10’s of meters beneath the earth’s surface.

2)__This type of magma produces relatively gentle eruptions, the lava is fast moving and has a low viscosity.

3)__This is an igneous rock of felsic composition. It is high in Si, K, and Na. It is low in Fe and Mg.

4)__This is a tongue of basaltic lava that quickly develops a tough plastic skin on contact with cold ocean water.

5) __This is the term for magma that has erupted and is flowing on the surface of the earth.

6)__This basaltic flow texture is rough, the lava has a high gas content.

7)__This basaltic flow is smooth and has a ropy texture.

8)__This is an igneous rock that is mafic in composition. High in Fe, Mg, Na. Low in Si.

9)__These lava flows are extremely slow moving. The lava is very viscous.

10) __This rock has a glassy texture from cooling rapidly.

11) __ This is an igneous rock of intermediate composition found in subduction zones.

12) __Clastic rock formed primarily of volcanic material.

Part b) True or False:

                Mark T (true) or F (false) in the blank provided:

                                1)__High eruption temperatures are typically around 600 to 800 degrees Celsius.

2)__The eruptions in Hawaii are basaltic.

3)__Andesitic lava flows are sluggish, this can lead to the plugging of the central vent and an explosion.

4)__Krakatoa is an example of a rhyolitic lava flow.

5)__Yellowstone is an example of a phreatic eruption.

6)__In phreatic eruptions, hot, gas rich magma reaches cold seawater, releasing superheated steam.

7)__Vesicular rhyolite can float on water.

8)__Mt. St. Helens is an example of an andesitic eruption.

9)__The lower the magmas gas content, the more explosive the eruption.

10)__Magma is less buoyant than surrounding rocks and tends to pool at the bottom of rock formations like synclines.