Tectonic Processes & Hazards - EQ1 - 1.3B - Volcanoes Flashcards
To be a hazard, it must..
affect people in some way, for example how damage of livestock affects the farmer and food supplies
In most cases, only …………………………… found at ………………………… represent a significant tectonic hazard.
In most cases, only large composite volcanoes found at destructive plate margins represent a significant tectonic hazard.
In most cases, only large composite volcanoes found at destructive plate margins represent a significant tectonic hazard. These eruptions often have…
- lava flows, pyroclastic flows, lahars and extensive ash and tephra fall that can affect areas up to 30 km from the volcanic event
Give a case study for the hazard of ash clouds
(79 AD) Mount Vesuvius, Italy
What was the danger of ash clouds in the case study of Mount Vesuvius
- Population can be poisoned by the deadly gas and
- subsequently buried under meters of ash during eruption
Give a case study for the hazard of steam eruptions and mud flows
Mount Rainier, Washington (1984)
What was the danger of steam eruptions and mudflows in the case study of Mount Rainier, Washington (1984)
- Mixtures of volcanic debris and water can form when heat from a volcano melts ice or snow on the mountain.
- The resulting meltwater can flow rapidly down the slopes, inundating the land and washing away buildings.
Give a case study for the hazard of pyroclastic flows
Mount Merapi, Indonesia (2010)
What was the danger of pyroclastic flows in the case study of Mount Merapi, Indonesia (2010)
- Pyrocastic flows send floods of hot rocks and gas down the mountain’s steep flanks- incinerating anything in the path population and buildings.
Give a case study for the hazard of lava flows
Mount Nyiragongo, Congo (2002)
What was the danger of lava flows in the case study of Mount Nyiragongo, Congo (2002)
- The laval flow forces people to evacuate and leaves people homeless due to the collapsed destroyed buildings
What are primary hazards from volcanoes?
- lava flows
- pryoclastic flows
- tephra and ash falls
- gas eruptions
What are secondary hazards from volcanoes?
- lahars
- Jökulhlaups
Where do lava flows occur
- subduction zone volcano (composite)
- hot-spot volcano (shield type)
What are lava flows
- Streams of lava that have erupted from a volcano onto the Earth’s surface
- They are very hot (reaching up to 1170°C) and can take years to cool completely
- Extensive areas of solidified lava can extend several kilometres from volcanic vents if the lava is basaltic and low viscosity
- It can flow at up to 40 km/h
What is the danger posed by lava flows
- Lava flows are generally not a threat to humans, because most of them move so slowly that people can easily get out of their way
- Nevertheless, they do destroy everything in their path so settlements can be lost
……….. are considered to be the most dangerous volcanic hazard
Pyroclastic flows
What are pyroclastic flows
- Flows consist of a dense mixture of superheated tephra (extremely hot up to 700°C)
- and poisonous gases erupted from a crater,
- moving down the sides of volcanoes
- and into the surrounding area at great speed (up to 700 km/h).
What is the danger of pyroclastic flows
- Any buildings or people in the way are destroyed through impact, burying, incineration or poisoning
- but because they move so quickly, they are far more dangerous than lava flows
- The deposition of material may also block river channels and cause flooding
Where do pyroclastic flows occur
- Subduction zone volcano (composite)
What is tephra
Tephra are pieces of volcanic rock and ash that blast into the air during volcanic eruptions.
What is ash
- The smallest fragments erupted from a volcano
- Ash can be forced to a high altitude and are so light that they can be carried around the planet in the atmosphere.
What is the danger of ash
- Ash falls are very disruptive
- Where the ash lands, it covers everything causing poor visibility and slippery roads
- Roofs may collapse under the weight, and engines may get clogged up and stop working (as was the fear with the Eyjafjallajökull ash cloud)
- Ash clouds disrupt flight paths of aeroplanes as it damages engines and fuselages.
What is the danger of tephra
- The larger pieces tend to fall near the volcano, where they can cause injury or death (as well as damaging structures).
