front 1 Which statement about May, 1980, eruption of Mount St. Helens is false? | back 1 The most powerful explosive event event was preceded by a massive landslide. |
front 2 Considering the history of Mt. Helens and Kilauea volcanoes and your knowledge of volcano types in different tectonic settings, if you had to live on a volcano, which of the following would you choose if safety was your only concern? | back 2 Mauna Loa in Hawaii, on the Big Island of Hawaii near Kilauea |
front 3 __________ is the major dissolved volatile constituent in both magmas and volcanic gases. | back 3 Water |
front 4 Which of the following factors help determine whether a volcanic eruption will be violent or relatively quiescent? | back 4 All of these |
front 5 ________tend to increase the explosive potential of a magma body beneath a volcano. | back 5 High viscosity and dissolved gas |
front 6 Which magma type would generally have the lowest viscosity? | back 6 Basalt |
front 7 Which one of the following shows the correct order (left to right) of decreasing magma viscosity? | back 7 Rhyolite, andesite, basalt |
front 8 What type of volcanic material is indicative of eruption under water? | back 8 Pillow lavas |
front 9 As magma approaches the surface, water contributes to the explosive potential of eruption because_________. | back 9 Water dissolved in magma flashes to steam as pressure decreases, and the volume increase leads to an explosive potential. |
front 10 Volcano A erupts rocks with SiO2 content ranging from 49% for 52% whereas volcano B, 100km away, erupts materials with SiO2 content of 62-68%. Which statement best characterizes these two volcanos? | back 10 Volcano A is probably a shield volcano with typically quiescent eruptions, whereas Volcano is likely a stratovolcano characterized by violent, explosive eruptions. |
front 11 Which type of basaltic lava flow has fairly smooth, unfragmented, ropy surface? | back 11 Pahoehoe |
front 12 Volcanic bombs originate_________. | back 12 As erupted magma blobs that partly congeal before falling to the ground |
front 13 _______ magma is the most abundant type of magma erupted on Earth. | back 13 Basaltic |
front 14 _________are usually the most abundant gases emitted during basaltic volcanism. | back 14 Water and carbon dioxide |
front 15 Which type of basaltic lava flow had its surface covered with sharp-edged, angular blocks and rubble? | back 15 AA |
front 16 Which of the following is not considered pyroclastic debris? | back 16 Pahoehoe |
front 17 The rock pumice often floats yet the density of the rock is greater than water. Why does it float? | back 17 Pumice is a pyroclastic rock comprised largely of open voids formed by gases released when the magma solidified as forth-life material. |
front 18 Pillow lavas are________. | back 18 Basaltic lava tubes erupted on the seafloor in volcanic piles analogous to toothpaste extruded from a tube. |
front 19 Which of the following volcanic types | back 19 no data |