9.2 Review

What factor determines a magma's viscosity?

• Gas content
• Temperature
• Silica content
• Type of eruption

Which type of magma is most resistant to flow due to its high silica content?

• Basaltic
• Andesitic
• Rhyolitic
• None of the above

Which type of magma has the least amount of silica?

• Rhyolitic
• Basaltic
• Andesitic
• None of the above

Where do basaltic magmas tend to form?

• Continental hot spots
• Subduction boundaries
• Rifts and oceanic hot spots
• None of the above

How often do volcanoes with andesitic magmas tend to explode?

• Rarely explodes
• Sometime explodes
• Usually explosive
• None of the above

What are the main gasses found in magmas?

• Oxygen and sulfur
• Helium and hydrogen
• Water vapor and carbon dioxide
• Nitrogen and phosphorus

What term describes basaltic lava flowing quickly forming smooth ropelike surfaces?

• Pahoehoe
• Aa
• Rhyolite
• Scoria

Which material class has the smallest pyroclastic fragments?

• Lapilli
• Ash
• Blocks + bombs
• None of the above

What shape does underwater lava cooling form?

• Pillowlike
• Columnar jointing

Pahoehoe