Tectonics 3.1.2 Flashcards
name the three types of lava
Basaltic, Andesitic and Rhyolitic
Name the lava that has a medium silica content
Andesitic lava
Name the lava that has a low silica content which means it has low viscosity
Basaltic lava is runny due to the low silica content and low viscosity
Name the lava that has a high silica content meaning it has high viscosity
Rhyolitic lava is really thick due to the high silica content which makes means it has high viscosity
describe the characteristics of where Basaltic lava occurs
Basaltic lava occurs in an effusive eruption from a shield volcano. The magma is fluid and allows pressure release so it’s less explosive
Describe the characteristics of where Rhyolitic and Andesitic lava occurs
Both types of lava occur at explosive eruptions at composite or cinder cone volcanoes. It is highly explosive due to the high silica content, which means it solidifies on the way to the surface, building up the pressure as the gas is trapped in air pockets
list 5 features of a composite volcanoes
- Occurs at convergent boundaries where there’s subduction zones
- very high and consist of many layers from hardened lava, tephra, ash and pumice
- steep gradient of up to 30
- High silica and water content
- Explosive eruptions
list 4 characteristics of a shield volcano
- occurs at divergent boundaries experiencing ridge push or at hotspots
- fluid lava as it is Basaltic
- Effusive eruptions, low viscosity
- gentle slopes 2-10
List characteristics of a cinder cone volcano
- Found on the sides of a composite or shield volcano
- it is a steep conical hill of tephra that has accumulated around a vent
- medium to high viscosity
- explosive and only last one eruption as they are weak
name the 4 primary volcanic hazards
- Tephra
- Lava flow
- Pyroclastic flow
- Volcanic gases
name the 2 secondary volcanic hazards
- Lahars
- Jokulhlaups
explain features of tephra
Tephra is combination of ash and volcanic bombs, which is ejected out as fragmented material
explain features of pyroclastic flow
Pyroclastic flows are hot rock fragments (lava and ash) which glows as it surges downhill rapidly, it is red hot up to 1000 degrees c
explain features of volcanic gases
volcanic gases is dangerous because they are denser than air, so sinks
Lake Nyos is an example of how dangerous it is, as it suffocated a town of 1,700 people (where 1747 people in total died from this eruption)
Explain features of a lahar
A lahar occurs when ice and snow melts or when ash is washed down by rainfall turning it into a mudflow of sediment and ash, that rapidly runs down the volcano
Explain the features of a Jokulhlaup
It is the same as a lahar, but it is a full glacier that melts and rushes down the volcano
name the two primary impacts of volcanic hazards
- Social impacts- 91,000 deaths due to suffocation and thermal injuries from major hazards between over just a century- shows how regions are affected
- Environmental impacts- local/regional scale impact due to landslides and lahars reshaping the landscape, destroying vegetation in the process
name the three secondary impacts of volcanic hazards and in what scale
- Economic- a regional scale impact is significant due to the financial loss estimated $65 million a year due to clean ups and repairs
- Environment- Large global impact due to the GHG emissions being released
- Social- average of 15,000 people left homeless every year is a local scale impact
When comparing eruptions case studies you must remember these 7 characteristics
- date- if they are similar or not
- measure of eruption using VEI
- Characteristics of the eruption
- what precautions have been taken
- death toll
- homelessness
- other factors and the scale of those impacts
E15 is a good eruption to compare to, as Iceland is a HIC and prepared
List the 7 features for E15
- 2010, Iceland one month
- VEI 4
- Ash plume 30km high, composite, subglacial, so vaporised the glacier in the crater
- 700 evacuated, given 30 min warning of floods
- 0 deaths
- 0 homeless
- Ash plume was blown southeast to Europe, led to airspace shutting down for 6 days
- 95,000 flights cancelled, leaving 1 mill people stranded
- $5 billion economic loss to European’s economy
Name two eruptions that are ideal to compare against E15
- Lake Nyos 1986- 1,746 people died, mainly due to suffocation of a a whole town as 100,000 tons of carbon was released, lake chemistry altered
- White Island, NZ 2019- 22 deaths, pyroclastic flow, phrenic eruption (steam blast eruption)
