Volcano WebQuest Follow-Up

A volcano is:

• An opening in the earth’s crust that allows magma, pyroclasts, and gases to escape

Volcano Features:

• Dome: build up of lava and debris surrounding a vent to form a volcano

• Vent: the opening in the earth that volcanic materials get erupted from

Things that can come out of a volcano:• Lava: molten rock, ability to flow depends on

Silica and moisture content (called magma when found inside the earth), made up of crystals volcanic glass, and bubbles

• Ash: rock, mineral, volcanic glass (all pieces ejected are around the size of a pinhead)

• Tephra: fragments exploded from a volcano (bomb, block, lapilli, ash, cinder)

• Lahar: fast moving mix of rock pieces and water, like a fast moving river of muddy rock

• Gas: CO2, H2Ovapor, SO2

• Pyroclastic Flow: avalanche of hot volcanic materials, travel very quickly

People tend to live near volcanoes because:

• They have very fertile soils• Contain valuable mineral deposits• Are very scenic• Tourism

Bad things volcanoes can do to the environment:

• Destroy the land• Kill plants, animals, and people• Put deadly gases

into the air (short term)• Provide about 3%

of yearly CO2 output

Viscosity is:

• The ability of a material to resist flow.

How does viscosity effect an eruption?

• The more viscous the lava, the more explosive the eruption.

• More viscous materials flow very slowly so they ‘jam up’ the volcano vent until there’s too much pressure and they explode.

Stratovolcano

• Lava viscosity=High• Gases: high which leads to explosive eruptions• Size: medium • Eruption Style: alternates eruptions of lava

flows and pyroclastic flows/explosions• Found: subduction zones• Examples: Mt Fuji, Mt St Helens,

Krakatoa

Cinder Cone• Lava viscosity=Highest• Gases: high, gas charged lava carries lava up in lava

fountains• Size: smaller with narrow piles of pyroclastic

particles• Eruption Style: explodes vertically with small

cinders forming and falling straight back down• Found: typically found on sides of other volcanoes• Examples: Paricutin, Wizard Island

Shield Volcano• Lava viscosity=Low• Gases: low• Size: largest , big base with gently sloping

sides• Eruption Style: fluid flow from all directions

around vent• Found: Hotspots• Examples: Hawaii,

Galapagos, Iceland

Hotspots are:

• Areas of volcanism not at plate boundaries.• Magma finds a weak spot in the earth’s crust

and forces it’s way up to the surface.• Ex: Hawaii, Yellowstone

How was Hawaii formed?• The Pacific Plate is moving Northwest over the

stationary hotspot that supplies magma to the Hawaiian volcanoes.

• As a result, an island chain formed with the oldest volcano being the furthest NW and the youngest (and still activeone) being the furthest

south.