HAZARDS 4 - Volcanoes Flashcards
(26 cards)
What is basalt?
Dark black to grey dense to fine grained igneous rock
What are seismographs?
An instrument that measures and records all details of earthquakes, such as fore and duration
What is distribution?
The way something is spread out or arranged over a geographic area / spatially
What is a supervolcano?
A volcanic centre that has an eruption of magnitude 8 on the VEI
What is an extinct volcano?
A volcano that hasn’t erupted from the volcano
What is an active volcano?
Having recent history of eruptions > likely to erupt again + erupted in living memory
What is a dormant volcano?
Erupted since the last ice age > currently not erupted within historical data
What is magnitude?
The amount of material erupted from the volcano
What is a Lahar?
Hot or cold mixture of water and rock fragments that flow quickly down the slopes of a volcano
What is the distribution of volcanoes?
- along converging and diverging plate boundaries
- 95% on plate boundaries
- difficult to predict
What is núee ardente (growing cloud)?
Incandescent cloud of gas, ash and lava
What are the 5 ways to predict volcanoes?
- Seismic activity
- microquakes, rising magma + fracturing of rocks - Ground deformation
- bulging of the land caused by rising lava - Upward movement of iron-rich magma measured
- Rising groundwater temperature or gas content
- e.g. sulpher - Warning signs such as small eruptions, emission of gases, landslides and rock falls
What are mudflows and lahars?
Flows of ash, cinder, soil and rock that has been changed to clay by acids in volcanic gases and hot spring waters
What is an effusive eruption and its characteristics?
- lava based, little violence
- basaltic lava
- constructive + hotspots
- shield volcanoes (lower)
What is an explosive eruption and its characteristics?
- more pressure build up, explosion of ash, rocks, gases and lava
- acidic lava
- destructive margins
- composite volcanoes (taller)
What is tephra?
Rock fragments and particles ejected by a volcanic eruption
What is a shield volcano?
A broad domed volcano with gently sloping sides, characteristics of the eruption of fluid, basaltic lava
What is a composite volcano?
A conical volcano built up by many layers (strata) of hardened lava and tephra
What is a pyroclastic flow?
A dense, destructive mass of very hot ash, lava fragments and gases ejected explosively from a volcano and typically flowing at great speed
What is a caldera?
A large volcanic crater, especially one formed by a major eruption leading to the collapse of the mouth of a volcano
What are fissure eruptions?
Basaltic lava creating vast extensive lava eruptions. Cover hollows in the existing landscape
What are acid dome volcanoes?
Steep sided convex cones associated with thick, silica-rich gases lava that solidifies quickly. Deadly explosive and can cause pyroclastic flow
What are the impacts of volcanoes?
- Climate change
- Seismic activity
- Polluted water resources
- Pollution > acid rain
- Landslides
- Tsunami
- Lava flows
- Lahars
- Debris avalanches
- Pyroclastic flows
- Flooding
- Gases
- Ashfall
What are the two elements measuring risk of disaster?
Natural hazards and vulnerability
