Volcanoes

Conical or dome-shapes landforms
Magma rises from a magma chamber through a conduit (vent)
Volcanoes are built from the eruption of lava flows and the deposition of pyroclastic materials
The type of volcano that develops depends on:

Location of Volcanism

Where are most active volcanoes found?

Spatter Cones

Small cones - (only a few meters tall)
Composed of basalt
Associated with and built on top of lava flows
• Spatter Cone Example 1
• Spatter Cone Example 2

Cinder Cones

Also called Scoria Cone
Cinders (scoria of basalt or andesite) are erupted from a central vent
Loose cinders form a cone-shaped pile around the vent
Eruption style - Strombolian - results from bursting bubbles of gas in the magma
• Cinder Cone Example 1
• Cinder Cone Example 2
• Cinder Cone Example 3
• Cinder Cone Example 4
• Cinder Cone Example 5
• Cinder Cone Example 6

Shield Volcanoes

Built from pahoehoe lava flows - basalt
Shallow slopes with relatively flat tops (look like a shield lying on the ground)
Spatter Cones often develop
Summit calderas are common
Largest volcanoes in the world and Solar System
• Shield Volcano Example 1
• Shield Volcano Example 2
• Shield Volcano Example 3
• Shield Volcano Example 4

Stratovolcanoes

Also called Composite Cones
Steep-sided, composed of lava flows and pyroclastic deposits
Composition - andesite, dacite or rhyolite
Violent eruption - due to gas content and high viscosity magma
Ash deposits can be extensive
• Stratovolcano Example 1
• Stratovolcano Example 2
• Stratovolcano Example 3
• Stratovolcano Example 4
• Stratovolcano Example 5
• Stratovolcano Example 6
• Stratovolcano Example 7

Domes

Lava flows of andesite, dacite, rhyolite or obsidian - viscous lava - low gas
Typically steep-sided with relatively flat tops
Endogenous domes - lava builds the dome from the inside
Exogenous domes - lava builds the dome by flows on the surface
• Dome Example 1
• Dome Example 2
• Dome Example 3
• Dome Example 4
• Dome Example 5
• Dome Example 6
• Dome Example 7

Flood Basalts

Fissure eruptions of basalt lava flows covering 100’s to 1000’s of km².
• Flood Basalt Example 1
• Flood Basalt Example 2
• Flood Basalt Example 3

Calderas

Collapse structures
Form due to the eruption or draining of magma from the magma chamber.
May or may not be associated with a volcanic cone.
• Caldera Example 1
• Caldera Example 2

Sea Floor Volcanism

Most active form of volcanism

Hot Springs

Hot water resulting from recent or impending volcanic or magmatic activity.
Magma body cooling will heat surrounding groundwater.
Minerals dissolved in the hot water are deposited at the surface when the water cools or evaporates.
• Hot Springs Example 1
• Hot Springs Example 2
• Hot Springs Example 3
• Hot Springs Example 4

Erosional Remnant

Erosional remains of volcanic structures.
Cone structure is often removed by erosion
Central vent materials remain

Volcanic neck - vent of a volcano remains after the cone has been eroded away
Watch a short video to see the relationship between a volcanic neck and the cone.

Dikes - conduit for lava reaching the surface - often sheet-like structures
• Erosion Example 1
• Erosion Example 2
• Erosion Example 3
• Erosion Example 4

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