Vulcanicity Flashcards
1
Q
Where are most explosive eruptions and why?
A
Convergent boundaries, as the oceanic plate subducts large pressures build up.
2
Q
Constructive plate boundary eruption characteristics
A
- Basaltic lava
- Little violence as gas escapes easily
- Regular and often continuous
- eg Shield volcano
3
Q
Destructive plate boundary eruption characteristics
A
- Rhyolite lava
- Potentially explosive
- Lava shatters into pieces
- Lava bombs, ash and dust erupts
- Long dormant periods of eruptions
- eg composite cone
4
Q
Features of a volcano
A
- Plumbing system of a magma chamber
- Conduit system- pipe eg central vent
- Cone, raised opening which emits magma
5
Q
Factors effecting the eruptions of volcanos
A
- Lava types
- Amount of dissolved gases in the magma
- Viscosity of the magma
6
Q
Classifications of volcanos
A
- Hawaiian
- Strombolian
- Vulcanian
- Plinian
7
Q
Hawaiian volcano Characteristics
A
- Occur along fissures
- Molten lava spurts from a fissure and feeds lava streams gently
- Viscous basaltic lava
- Rarely produce volcanic ash
- Central vent spurts lava to a height of several feet
8
Q
Strombolian volcano characteristics
A
Eg Mount Etna Italy
- Huge clots of lava burst from the summit forming luminous arcs through the sky
- Lava consists of partially molten volcanic bombs that fly through the air
- Clots collect on the flanks of cones and stream down forming fiery rivulets
- Can produce ash clouds but are normally short lived
9
Q
Vulcanian volcano characteristics
A
Eg Sakurajima Japan
- High viscosity of magma
- Dense cloud of ash-laden gas explodes from crater
- Ash cloud rises above peak of volcano
- Bombs and blocks also ejected
- more violent and less frequent eruptions
10
Q
Plinian volcano characteristics
A
Eg Mount St Helens, USA
- Explosive ejections of relatively large amounts of viscous lava
- Send ash and volcanic gas high into the stratosphere
- Fast moving deadly pyroclastic flow is common
- Inject large amounts of sulphur dioxide into the atmosphere so decrease surface temperature of the earth
- lots of viscous lava
11
Q
Fissure volcano
A
- Basaltic lava
- Constructive margins
- Gentle and persistent eruptions
- Eg Heimaey Iceland 1973
12
Q
Shield volcano
A
-Hotspots
-Gentle and predictable
-Basaltic rock
A cone with long gentle sides made of many layers of lava
-Eg Mauna Loa in Hawaii
13
Q
Composite volcano
A
- Classically shaped
- Destructive plate boundaries
- Violent eruptions with volcanic bombs and lahars
- Andesitic lava
- Eg Mt Etna
14
Q
Acid volcano
A
- Steep sided cone
- Continental crust
- explosive and unpredictable
- Rhyolitic lava
- Eg Puy de Domes
15
Q
Cinder cone
A
- A symmetrical cone
- Concave sides
- Destructive boundaries
- Lava escapes from the base of the cone
- EG Paricutin
