Mod 2.2 Study Deck

Question 1

What is the evolution of Earth’s atmosphere and oceans?

Answer 1

Gases emitted during volcanic eruptions

Question 2

Differences between St. Helens Volcano Eruption vs. Kilauea Volcano in Hawaii?

Answer 2

1.) St. Helens Volcano = 1980 / Kilauea Volcano = 1983
2.) St. Helens Volcano = largest volcanic eruption in North America / Kilauea Volcano = non-explosive eruptions
3.) St. Helens Volcano = extreme aftermath/blew out north flank of volcano / Kilauea Volcano = relatively quiet outpourings
4.) St. Helens Volcano = killed 59 people (intense heat/suffocating, impact, and mudflows) / Kilauea Volcano = more than 180 home and national park visitor’s center destroyed (no people killed)

Question 3

Why are some volcanic eruptions explosive and others quiescent?

Answer 3

• Quiescent = effusive; outpourings (fluid lava); harmless; low viscosity (measure of fluid’s mobility)
  -Explosive = more spurts (lava); more intense eruptions; harmful; high viscosity (measure of fluid’s mobility); eruption columns (buoyant plumes of hot, ash-laden gases)

Question 4

Factors of an Eruption Type

Answer 4

Factors:
1.) Viscosity (measure of fluid’s mobility); depends on temperature and silica content; direct relationship to eruption type

2.) Gas content (basaltic, granitic, andesitic)

Question 5

Magma vs. Lava

Answer 5

-Magma = body of molten rock; gases = water vapor and carbon dioxide; including any dissolved gases and crystals
-Lava = erupted magma

Question 6

Location of Magma Generation

Answer 6

-Earth’s Upper Mantle
-Partial melting (solid rock)

Question 7

Magma Composition

Answer 7

• Basaltic rocks (dark color; high % dark silicate material; caused by seafloor spreading; eruptions = high % dark silicate materials; eruptions = highest temp)

-Granitic rocks (light-colored silicate materials; lower % silica; crust-mantle boundary; eruptions = lowest temp)

-Andesitic rocks = combo (granitic and basaltic rocks)

Question 8

Three categories of materials let go during volcanic eruptions

Answer 8

1.) Lava: flow (basaltic lava) = fluid; flow in thin, broad sheets; speed = > 30 km/hr (usually between 100 m - 300 m); flow (silica-rich rhyolitic lava) = very slow; 90% (total volume of Earth’s lava) = basaltic lava (eruptions = submarine volcanism (seafloor eruptions)

2.) Large volumes of gas: volatiles (gaseous components of magma dissolved in melt); gaseous portion = < 1% - 8% (total weight); form = water vapor

3.) Pyroclastic materials: broken rock, lava “bombs”, and ash; scoria = vesicular eject; produced during basaltic magma eruptions; ash and dust = explosive eruptions; size = very fine dust - sand-sized volcanic ash

Question 9

Pillow lava (definition)

Answer 9

Basaltic lava = solidifies underwater

Question 10

2 types (basaltic lava flows)

Answer 10

1.) aa flow (jagged, blocky surface); cooler
2.) pahoehoe flow (smooth-to-ropey surface); hotter

Question 11

Composition of Volcanic Gases

Answer 11

• H20
  -CO2
  -SO2
  -H2S
  -CO
  -N2