2a + B- Volcanic Activity + Hazards Flashcards
Lava flows as a hazard
- balsatic/basic lava can flow very far
- acidic lava is very thick = does not flow far
- main hazard to infrastructure, property, crops
Pyroclastic flows as a hazard
- hot gas + rock fragments travelling at high speed (100km/hr) = following shape of land
- inhalation of gas = death
Tephra as a hazard
- material ejected from volcano = ash or volcanic bombs
- ash can cause difficulty breathing
- smothers crops + disrupt ground/ air transport
Toxic gasses as a hazard
- range of dangerous gasses ejected from eruption
-chance of acid rain - can cause death
Lahars volcanic hazard
- mud flows
- often include large rocks + boulders
- high speeds = destroy + bury everything in path
Floods as volcanic hazard
- eruptions beneath ice = rapid melting
- water build up until it finds exit
- gushes out in torrent
Tsunami as hazard
- eruptions off an island displace lots of water = tsunami wave
Travel at 7000km/hr and can get to 25m by land
How do eruptions at hotspots happen and give an example
- hot spot = particularly hot section of mantle
- melt through crust causing volcanic activity
- movement of plates can move volcanoes away from hotspots causing extinct volcano
- hawaii
How do rift valleys form
Give an example
- rising magma creates domes
- plates continue to spread = rock fractures + dome subsides
- forms steep sided valley
- Africa rift valley
How are strato / composite volcanoes formed
- steep sided volcano made up of layers of ash + lava ejected during eruption
How are Sheild volcanoes forms
- Broard- based volcano with gently sloping sides
- formed by free flowing/ low viscosity lava travelling long distances
What is a super volcano and give example
- Volcano that erupts more than 100km^3 in a single eruption
eg: Yellowstone = erupted 700,000 years ago so overdue
Yellowstone is a result of Hotspot = however chance of a super-Volcano type eruption is very low =more likely to be a lava flow
What 2 factors make the VEI
Magnitude = amount of material erupted
Intensity= speed at which material is erupted
Combines Magnitude with Intensity into single number 0-8
its Logarithmic = increase in one number = 10x explosivity
What scale is the VEI on
- combines 2 factors for a number 0-8
- logarithmic scale so each increase in number represents a x10 increase in explosivity
How are volcanic arcs formed
- descending plate melts
- rises and forms land = new islands/ volcanic arc
