Volcanoes 1

Question 1

2 ways we study volcanoes

Answer 1

• study and monitor active systems
• forensic reconstruction

Question 2

What is magma?

Answer 2

melted rock IN earth (below surface)
- melt + crystals + bubbles

Question 3

What is lava?

Answer 3

melted rock exposed at earth surface
- melt + crystals + bubbles

Question 4

What is a volcano?

Answer 4

structure where magma is erupted at earth’s surface
- subaerial and subaqueous

«slides for diagram»

Question 5

How do volcanoes form?

Answer 5

1. magma created by melting of pre-existing rock in mantle & crust
2. reaches surface through fractures and erupts as lava or pyroclastic material

Question 6

When magma reaches earth’s surface through ____, it erupts as ____

Answer 6

fractures
lava or pyroclastic material (tephra)

Question 7

Extrusive volcanoes cool ____ and have ____ crystals

Answer 7

quick cooling, small crystals

Question 8

Intrusive volcanoes cool ____ and have ____ crystals

Answer 8

slow cooling, large crystals

Question 9

Describe the volcanic system (source and eruption regions, etc)

Answer 9

Eruption
- at surface

storage
- near crust

transport
- travel thru fractures
- ascend as dikes

source region
- mantle

Question 10

where is melt produced?

Answer 10

mantle

Question 11

dikes vs sills

Answer 11

dike is magma travelling up, sills is levelling out horizontally (cuz lost buoyancy)

Question 12

What is intrusive rock or igneous intrusions?

Answer 12

magma that freezes in the crust and is not erupted

Question 13

Example of eruptive volcano

Answer 13

Mt St Helens
- dome extrusion

Question 14

Igneous rocks cooled at surface are…

Answer 14

• extrusive / volcanic
• small crystals / fine grained
• rapid cooling

Question 15

Igneous rocks cooled below surface are…

Answer 15

• intrusive / plutonic
• large crystals / coarse grained
• slow cooling