Quiz 1 Flashcards
What is a natural hazard?
A natural, but extreme geological or meteorological event greatly exceeding human expectations in terms of magnitude or frequency and potentially causing significant material damage to humans and their property with possible loss of life.
Hazard mitigation
The effort to reduce loss of life and property by lessening the impact of disasters (can’t control natural events)
Five common approaches to natural hazard mitigation and management?
Accept the loss
Zoning regulations
Engineering solutions
Install and use warning systems/evacuation
Develop public use and abandonment of hazardous areas
Generalized form of scientific method(s) is
Formulate question Research the question Form a hypothesis Conduct an experiment to test hypothesis Analyze data Draw conclusions Reiterate, if needed Communicate results
Natural disaster
Major adverse event that affected humans resulting from geological or meteorological process.
Criteria:
-10 or more people killed
-100 or more people affected
-state of emergency declared or international assistance requested
Catastrophe
Massive disaster the requires significant outlay of money and long time (years) to recover
Why is studying the science of natural hazards important?
To help predict natural hazards, monitor and map hazardous events and processes, consequences of hazards can be minimized
What can be done to decrease risk associated with a natural disaster?
Mitigation - achieved through risk analysis, which results in information that provides a foundation (reduce risk)
- FEMA (Federal Emergency Management Agency)
- Moving people away from hazardous areas
- Make people aware of possibilities
What types of energy drive natural disasters?
Sun (nuclear fusion)
Gravity (including rides)(related to relief)
Natural radioactive decay/Earth’s internal heat (isotopes lose proton, so they decay ex: volcanic eruptions)
Impacts
What is plate tectonic theory?
Concept that earth’s surface is divided into a few large, thick plates slowly moving and changing in size. Intense geological activity at pates.
Types of plate boundaries
Convergent
Divergent
Transform (conservative)
How are plate boundaries recognized?
Mostly by locations of volcanoes and earthquakes
Driving mechanisms for plate tectonics?
Slab Pull (convergent) heavier plate moves under lighter one
Ridge Push - little mound being formed (little volcano or mountain)
Mantle convection (radiogenic heat) - heat released from radioactive elements.
Six common types/shapes of volcanoes
Fissure Shield Dome Ash-finder (cinder cone) Composite Caldera
What materials make up volcanoes?
Lava, ash, or both
What are the differences in shapes of the different types?
Fissure-super gentle slope (not even circle opening)(ex:Columbia River Plateau
Shield: Wide and low, gentle slopes with basaltic lava flow (circular opening)(ex: Kilauea
Dome: Steep, convex slope from thick, fast cooling lava; hardened, thick layers of rock (like little lava cake)(ex: Mt. Lassen)
Ash-cinder: steep, conical hill; small crater; lava flow comes from base (Mt. Tabor)
Composite: little branches of lava; steep hill; rough landscape, higher viscosity, so violent eruptions (Mt. St. Helens)
Caldera: Hole in ground (ex: Yellowstone)
Which type has little or no volcanic edifice?
Fissure volcano.
How does explosiveness relate to magma viscosity?
Magma with high viscosity= more violent eruptions
Magma with low viscosity = less violent eruptions
How does explosiveness relate to temperature?
Higher temperature=lower viscosity, so less violent eruptions
Lower temp =higher viscosity, so less explosive
(Think of honey)
Important aspects of household preparedness?
Personal hazard preparedness kit
Two places to meet (near home and farther away)
Emergency contact person
Practice evacuating
Describe stratovolcano/composite volcano.
Moderate in violent, but dangerous, moderate viscosity magma; lava and pyroclastic flows, steep sides
Explain a pyroclastic flow
A dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from volcano with great speed
What is a caldera?
How does it form?
Where? Relative to other volcanoes?
Relatively viscous lava, very violent, lava and pyroclastic flows (tuff).
Formed by collapse of volcano into itself, making a volcanic crater. Usually, triggered by emptying of magma chamber beneath volcano, as result of large volcanic eruption.
Can be part of larger volcanoes or independent.
Explain a lava dome.
High viscosity magmas, high violence, but small. Steep.
How does volatile/gas content relate to explosivity?
More dissolved gas = more explosive, due largely to trapped gases.
How doesn’t gas content relate to volcano type?
Stratovolcanoes and calderas have issues with trapped gases, so they’re more explosively. Shield volcanoes release gases, so less violent.
What are the most common gases in magmas/emitted from volcanoes?
Water vapor (steam), carbon dioxide (CO2). Together, they make up 98%. CO2 heavier than air, so can cause Geohazard. SOMETIMES hydrogen sulfide (rotten egg smell)
Why is CO2 that builds up in a crater lake a problem?
How can it be mitigated?
Because CO2 can leak into water that could be major source for town. Could lead to geohazard if earthquake occurs (gases could be released throughout nearby town)
Pump that lifts water from bottom of lake to the to, mixing the water.
Explain VEI
Volcanic Eruption Index.
(0-8). Used to relate eruptions, based on how much material is ejected, to what height, and how long eruption lasts.
What are some volcanic hazards?
Pyroclastic flows
Acid rain
Ash clouds
Lava flow
Two main types of igneous rocks based on WHERE they form?
Extrusive (volcanic rocks; aphanitic textures = small crystals, even glassy). Formed due to rapid cooling.
Intrusive (plutonic rocks; phaneritic textures = large crystals) formed due to slow cooling.
Based on COMPOSITION, main types of igneous rocks?
Felsic composition: High SiO2 (right in Al, K, Na) lighter in color.
Mafic composition: Low in SiO2 (rich in Mg, Ca, Fe) darker in color.
Where do volcanoes originate?
Why do they form in certain places?
Molten rock, magma, from within earth.
Convergent boundaries push together; hot spots because plume arises (either at relatively fixed location, or may be fixed and moves around).
Differences between oceanic and continental crust?
Continental: felsic (granite); less dense, more buoyant; mostly made by partial melting of mantle (chemically different because only portion of mantle is melted); thicker.
Oceanic: magic (basalt); more dense, less buoyant; made at spreading centers; thinner.
Explain convergent and divergent margins.
Subtypes of convergent margins.
Convergent: move towards each other.
Divergent: move away from each other (ex: mid-Atlantic ridge).
Oceanic-oceanic; oceanic-continental; continental-continental.
What type of magma is expected at each type of location?
Convergent: buoyant magma (rhyolitic magma in continental crust with high gas and silica continent)
Divergent: Basaltic magma
What causes a hot spot?
In what type of crust to hotspots form?
Mantle plumes, which are upwelling of abnormally hot material/rock within earth’s mantle.
Oceanic crust.
How can you identify volcanoes that are active, extinct, and dormant?
Active: HAVE erupted in past 10,000 years.
Dormant: Have NOT erupted in past 10,000 years, but are expected to erupt again; no erupted recorded in history, show no signed of current activity; but not deeply eroded.
Extinct: Not expected to erupt again; deeply eroded.
One type of information used to forecast volcanic eruptions?
Ground deformation (bulging/tilting of ground)
Seismicity
Changes in volcanic gas composition
Increase in surface temperature
Tilt meter and GPS.
Tilt meter: tries to detect inflation of underlying magma chamber, addition of material or explosion of gas.
GPS: Geodesy and other measures show that the plates move in different directions; tries to detect same as tilt meter.
