Chapter 5
The Columbia Plateau in Washington and Oregon is ________. 1. a flood basalt plateau 2. a thick stack of welded-tuff layers 3. a caldera filled with rhyolite lava flows 4. a field of a large stratovolcano
1. a flood basalt plateau
Which type of volcanic hazard results in a very fast-moving cloud of super-heated ash and toxic gases? 1. pyroclastic flows 2. aa flows 3. block lavas 4. lahar flows 5. pahoehoe flows
1. pyroclastic flows
Which region has the greatest concentration of currently active volcanoes? 1. the circum-Pacific area 2. the area surrounding the Red Sea 3. the coastal plain of western Africa 4. European Russia and Siberia
1. the circum-Pacific area
The 1991 Pinatubo eruption in the Philippines caused brilliantly colored sunrises and sunsets to be seen for the next few years. What caused this phenomenon? 1. Radioactive atoms blown into the atmosphere glowed red as they decayed. 2. Sulfur dioxide and other erupted gases formed aerosols in the stratosphere. 3. The eruption added large amounts of carbon dioxide to the atmosphere. 4. The eruptive cloud destroyed parts of the Earth's protective ozone layer.
2. Sulfur dioxide and other erupted gases formed aerosols in the stratosphere.
Which one of the following statements concerning cinder cones is FALSE? 1. They are built mostly or entirely during one eruptive cycle. 2. The cinders and other pyroclastic particles are consolidated into welded tuff. 3. They are small volcanoes with fairly steep sides. 4. The cinders most commonly are basaltic.
2. The cinders and other pyroclastic particles are consolidated into welded tuff.
What layers make up a composite volcano, such as Mt. Rainier? 1. flood basalts and ash 2. Pahoehoe lava with cinders 3. lava tubes and pahoehoe 4. Cinders, ash, and lava flows 5. pillow basalts and ash
4. Cinders, ash, and lava flows
The 1943 eruption of Paricutin in Mexico was characterized by ________. 1. mudflows and explosive ash eruptions 2. welded-tuff deposition and caldera formation 3. pyroclastic eruptions and nueé ardente flows 4. cinder cone building and basaltic lava
4. cinder cone building and basaltic lava
Which kind of eruptive activity is most likely to be highly explosive? 1. lava flows from a large cinder cone complex 2. fissure eruptions feeding lava to flood basalt accumulations 3. lava flows from a large shield volcano on an oceanic island 4. eruptions of big, continental margin, composite cones or stratovolcanoes
4. eruptions of big, continental margin, composite cones or stratovolcanoes
Which of the following best describes seamounts and islands of the deep ocean basins? 1. andesitic pyroclastic rocks submerged when the mountains sank below sea level 2. huge granite batholiths intruded beneath the ocean floor 3. domed gabbro intrusions and massive, submarine, rhyolitic, pyroclastic cones 4. piles of basaltic lava flows built up from the ocean floor by multiple, summit and flank eruptions
4. piles of basaltic lava flows built up from the ocean floor by multiple, summit and flank eruptions
T/F: In general, cinder cones are much larger than shield volcanoes.
False
T/F: Most basaltic magmas are believed to form by partial melting of granite in the lower crust and upper mantle.
False
A cave-like formation created by the outside-in cooling of pahoehoe lava flows.
Lava tube
A type of lava with a ropy, often folded or wrinkled surface
Pahoehoe
Bulbous bodies of basalt, indicating that the lava cooled underwater.
Pillow lava
T/F: Basalt is the most common magma erupted along oceanic rift systems.
True
T/F: Repeated eruptions of relatively fluid lava from fissures can eventually cause an area to be covered by flood basalts.
True
T/F: Vents that emit only heated, volcanic gases and water are called fumaroles.
True
________ is a major dissolved volatile constituent in both magmas and volcanic gases. Carbon monoxide Water Methane Hydrogen chloride
Water
Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble? scoria pillow lava aa pahoehoe
aa
Mount St. Helens is ________. an explosive stratovolcano a basaltic cinder cone a small, welded tuff cone a basaltic shield volcano
an explosive stratovolcano
Kilauea and Mauna Loa are ________. explosive, rhyolitic volcanoes basaltic shield volcanoes small, basaltic cinder cones andesitic stratovolcanoes
basaltic shield volcanoes
A volcano made up of a small pile of cinders, lapilli, and lava, which tends to form in a few days or weeks of an eruption.
cinder cone
Pebble- to cobble-sized fragments of volcanic material
lapilli
A very low-density volcanic rock with a vesicular texture, light color, and an andesitic to rhyolitic composition
pumice
The term describing a fluid's resistance to flow; applies to magma and lava
viscosity