Volcanoes 1

Question 1

What is the distribution of volcanoes similar to?

Answer 1

very similar to earthquakes but not exactly the same

Question 2

Magma

Answer 2

high temperature, molten or(mostly molten) rock material with a wide range of compositions(silica almost always present)

Question 3

Where does melting actually occur?

Answer 3

-in the overriding plate

Question 4

Classifications of Magma

Answer 4

Lowest silica content- basaltic magma at 50%

Intermediate silica content- andesitic magma at 60%

Highest silica content- rhyolitic magma at 70%

Question 5

Melting Temperatures

Answer 5

Low silica around 1200

High Silica 700-900

Question 6

Dissolved volatiles such as gas and fluids determine what?

Answer 6

eruptive behavior

Question 7

Flood or Plateau Basalt

Answer 7

very liquid lava; flows very widespread; emitted from fractures
ex: columbia river plateau

Question 8

Shield Volcano

Answer 8

• liquid lava
• emitted from a central vent
• large
• sometimes has a caldera collapse
  ex. Hawaiian Volcanoes

Question 9

Cinder Cone

Answer 9

• explosive liquid lava
• small
• emitted from a central vent
• if long enough may build up a shield volcano
  ex. Crater of the moon

Question 10

composite or stratovolcano

Answer 10

• more viscous lavas
• explosive debris
• large
• emitted from a central vent
  ex. Mount Rainer, Mount St, Helens

Question 11

volcanic dome

Answer 11

• very viscous lava
• relatively small
• can be explosive
• commonly occur adjacent to crater of composite volcanoes
  ex. Mount St. Helens Lava Dome

Question 12

Caldera

Answer 12

very large composite volcano collapsed after an explosive period
-frequently associated with plug domes

Question 13

Lava

Answer 13

is magma that has been extruded from a volcano

Question 14

Elemental Composition of Magma

Answer 14

• O
• Si
• Fe
• Al
• Mg
• Ca
• Na
• K