Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
36 Cards in this Set
- Front
- Back
|
Explain what magma density and magma viscosity are
|
- Density: less dense, rises
- Viscosity: Resistance to flow. I.e. low viscosity lava is runny |
|
|
List the different categories of volcanic rocks and explain the differences between the magmas they came from
|
- Felsic rock (from Felsic magma: high visc.) - rich in low density minerals (quartz, felspar), light colour, low density
eg. granite - Mafic rocks (from Mafic magma: low visc.) - rich in denser minerals (olivine, pyroxene) dark colour, denser. eg. gabbro |
|
|
Mafic rock
|
(from Mafic magma: low visc.) - rich in denser minerals (olivine, pyroxene) dark colour, denser. eg. gabbro
|
|
|
Felsic rock
|
(from Felsic magma: high visc.) - rich in low density minerals (quartz, felspar), light colour, low density eg. granite
|
|
|
Explain why some magmas erupt explosively (as pyroclastic material) and some magmas erupt effusively (as lava)
|
- low viscosity magmas flow easily out of the volcano, while high viscosity builds up pressure, air bubbles, explodes
|
|
|
Explain the differences between pahoehoe and a'a lavas
|
- Pahoehoe flow smooth and ropey (low viscosity)
- A'a: while how and smooth underneath, have crumbling rocks on top (high viscosity) |
|
|
Describe the distribution of the world's active volcanoes
|
- Plate boundaries primarily - Ring of Fire
|
|
|
List the three types of plate boundaries and the different types of volcanoes that occur at these plate boundaries
|
- Divergent boundaries: pull away from each other
- Convergent boundaries: one pushes under another. Many volcanoes seen at subduction zones - Transform boundaries: sliding past each other |
|
|
Describe the type of volcanoes that occur at hot spots
|
- Usually shield volcanoes
|
|
|
Describe the morphology, dominant rock type and typical eruption style of the different types of volcanoes
|
- Cinder cones: mafic (basalt), explosive Layers of pyroclastic ejecta. Erupt for a few years then never again --> Paracutin, Mexico
- Shield: mafic, non-explosive. Erupts often, predictable, flows down slopes smoothly --> Hawaii - Stratovolcanoes: intermediate, mixed. Large, steep edifice. Erupt every 10 - 1,000 years. Interbedded lava flows, pyroclastic flows, lahars. May erupt many times, active for 100,000 years ---> Mt. Baker - Calderas: felsic, explosive --> Yellowstone |
|
|
Lahars
|
h
|
|
|
Pyroclastic flows
|
h
|
|
|
Calderas
|
h
|
|
|
Describe the tectonic setting of Southern BC (Cascadia) and determine the dominant type of volcano that occurs here
|
- Juan de Fuca plate
- Stratovolcanoes are dominant |
|
|
Explain what lava flows, fire fountains, lava boys and volcanic ash are and how they form
|
- Lava flows
- fire mountains - lava bombs - volcanic ash |
|
|
Lava flows
|
- more slowly, rarely kill
- formed by flow out of earth, or drops from fire fountain coalescing. - can cause massive property damage |
|
|
Fire fountains
|
- when basaltic lava contains a significant amount of gas, small explosive eruptions with lava upshots may occur
|
|
|
Lava bombs
|
large chunks of rock, cooled lava, fall from explosion
|
|
|
Volcanic ash
|
Covers a large area downwind of the volcano and can be very deadly
- the loud of small, still incredibly hot material that rises from explosion - darkness, suffocation, roofs collapse |
|
|
Describe the different types of volcanic eruptions and how they are related to magma properties
|
- Effusive (low visc.): outpouring of molten magma from the vent
- Explosive (high visc.): gas driven violent eruptions - Fissure eruptions: Often extend radially from volcano centre. Related to regional tectonics |
|
|
Pyroclastic flows
|
- Avalanches of hot pyroclastic material, air, and gas.
Most common origin: collapse of volcanic column |
|
|
Lahar
|
- Indonesian word for volcanic debris flow. Flows of water and loose volcanic debris. Prevalent at snow/ice clad volcanoes. Can happen in pulses
|
|
|
Jokulhlaups
|
flood
|
|
|
Dome collapse
|
followed by pyroclastic flow
|
|
|
Later blast
|
-Comparatively cool to other activity. Fast and devastating
|
|
|
Volcanic gases
|
- typically highly acidic (pH 1). Kills plants and animals. Major constitutes include H2), CO2, SO2, HF.
People die from asphyxiation. |
|
|
Explain what a volcanic hazard map is and why they are useful
|
- Maps the different hazards to the areas they can affect. Nearby populations can be evacuated accordingly
|
|
|
Explain how the size of a volcanic eruption is estimated
|
- VEI - Volcano Explosivity Index
- Volume of ash produce - Volume of eruption cloud above the vent - Duration of the eruption - Logarithmic scale like Richter. 4 is 10 times larger than 3. |
|
|
List the different volcano monitoring techniques and the instruments that are used and explain what they are used for
|
- Seismic monitoring: most important tool for monitoring and forecasting. Ideal seismic network have 6+ stations within 15KM of each other to locate depth of quakes
- TM (tiltmeter): Measures changes in angle and slope - GPS (global positioning system): measures changes in position - EDM (electronic distance meter): meausres changes in distance between two points - InSAR (Interferometric Synthetic Aperture RAdar): Measurements by satellites detect changes in elevation (cm to m) |
|
|
Seismic monitoring
|
most important tool for monitoring and forecasting. Ideal seismic networks have 6+ stations within 15KM of each other to late depth of quakes
|
|
|
TM (Tiltmeter)
|
Measures changes in angle and slope
|
|
|
GPS (Global positioning system)
|
measures changes in position
|
|
|
EDM (electronic distance meter)
|
measures changes in distance between two points
|
|
|
InSAR (Interferometric Synthetic Aperture Radar)
|
Measurements by satellites detect changes in elevation (cm to m)
|
|
|
Discuss the way British Columbia's volcanoes are monitored
|
- gas monitoring - by measuring the amount of a specific gas in plume and wind speed, we can calculate the emission rate. Look through volcanic gas by examining light from sun: CO2 and SO2 have distinct signals when they deflect light
- COSPEC - correlation spectrometer - Fourier transform infra-red spectrometer (gas) - Direct sampling |
|
|
Evaluate the hazards to Vancouver associated with an eruption from Mt. Baker
|
- Significant lahar hazard in surrounding valleys (Abbotsford)
- Lava and Pyroclastic Flow hazard is low risk, uninhabited area - Ash fall hazard for all of Greater Vancouver Area & S. BC. YVR closed, traffic chaos, UBC/SFU closed, Respiratory problems |
