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Most of the Earth's explosive volcanoes are located in a zone that encircles the Pacific Ocean called the Ring of Fire. The types of volcanoes that commonly form in this zone are called _____________ that form by the melting of asthenosphere and lithosphere rocks during _____________.
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| stratovolcanoes, subduction |
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| Melting of the mantle forms the most common type of magma that is extruded onto the Earth's surface because ____________. |
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| high temperatures allow magma to rise to the surface before crystalizing completely to become solid rock, low percentage of SiO2 so it has low viscosity, extruded in rift zones where fractures provide avenues for flow |
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| Subduction zones are characterized by ______________. |
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| steep-sided volcanoes composed of alternating pyroclastic debris and lava flows, pyroclastic flows and calderas, andesitic to rhyolitic volcanic rocks |
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| Floods associated with melting of glaciers during a volcanic eruption are referred to as _________. |
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| What gases are commonly emitted in a volcanic eruption |
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water vapor, carbon dioxide, carbon monoxide and methane.
NO NITROGEN!!! |
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| What gas killed a lot of people and animals near Lake Nyos in 1986? |
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| During 1986 Lake Nyos eruption the most dangerous areas to be in were |
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| In valleys because the gas was more dense than air |
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| The violent flank eruption of Mount St. Helens in 1980 was set off by __________. |
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| an earthquake caused a collapse of part of the mountain, rapidly releasing pressure. |
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| Melting of thick caps of snow on volcanoes can generate what hazard |
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| When magma is too viscous to flow it can form a sticky blob that blocks the conduit of a volcano and forms a steep sided feature known as a ___________. |
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| what you find on a continent adjacent to a subduction zone |
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| a chain of steep-sided volcanoes subparallel to the subduction zone |
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| What killed 28k people in St. Pierre near Mt.Pelee and destroyed the town |
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Definition
| a gaseous flow of incandescent volcanic ash and dust |
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| What causes a pyroclastic flow to move at high velocities? |
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| Gravitational collapse of an eruption cloud, energy from the eruption, internal turbulance that keeps particles in the air, release of gas from magma particles and heating of surrounding air creating a "popcorn" effect |
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| Why are pyroclastic flows one of the most dangerous types of hazard associated with volcanic eruptions |
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| form with little or no warning and move at extrememly high velocities, cover large areas with a dense cloud of ash and dust that can choke an entire city, temperature of the cloud sveral hundred degrees causing fires |
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| Lahars created on stratovolcanoes have high destructive energy because |
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| they are a dense mass of water and rock that flows down steep slopes over thousands of feet of elevation |
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| What continental hot spot in the United States has posed the greatest threat in historic times |
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| melting of snow cap on volcano, flow of pyroclastic material into a river, heavy rainfall during an eruption of pyroclastic material, collapse of crater lake or dam |
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| Describe a pyroclastic flow |
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| a flow of hot gas and ash |
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| Name some hazards to humans that are related to volcanic eruptions |
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Definition
| burial by volcanic generated mudflows, asphyxiation from volcanic gases, tsunami, being struck by pyroclastic debris |
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| Two most frequent causes of death from volcanic eruptions are |
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Definition
| pyroclastic flows and tsunami's |
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| Downslope movements of earth materials can be triggered by |
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| earthquakes, sonic booms, heavy rainfall, volcanic eruptions |
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| Creep is typically caused by |
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Definition
| slow movement of soil downslope by contraction and expansion of clay rich soils |
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| The upper part of a landslide is a zone of ________ and the lower part is a zone of_____________ |
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| Water can weaken earth materials and cause subsurface erosion by __________ |
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| piping, dissolving the cement between grains |
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| What orientation of rock layers poses the greatest potential hazard for mass movement |
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| layers dip in the same direction as the slope, but the dip of layers is less than the slope |
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| What are some clues to look for when looking for signs of creep |
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| trunks of trees are curved downslope, telephone poles tilted downslope, fence lines form a u-shape that points downslope, surface of the ground is bumpy and resembles pudding |
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| The rate of mass movement will tend to _________ with an increase in water content |
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| Name something that can enhance the strength of a hillside |
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| the cohesion of the mass and its weight |
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| Which country has had the highest number of recorded fatalities due to mass movements in the past 500 years |
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| Near vertical movement of material from a steep cliff or slope |
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| viscous, turbulent movement of material over the landscape |
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| Movement on top of a basal slip surface as a semisolid mass |
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| Whatr are possible surfaces along which slides can move |
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| planes between layered rocks, fractures, soil seperated from rock by a 2 meter thick layer of clay, water-saturated succesion of rocks lying on granite |
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| Massive rock falls that are transformed into long, fluidized flows of rock and debris are called |
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| Large blocks of snow that behave like rock slides are known as |
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| Which country has the highest reported number of deaths per year related to snow avalanches |
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| The mass movements at Turnagain Heights, Alaska which were triggered by the M9.2 earthquake in 1964, is a good example of _____________ |
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| what dissolved gas helps in the dissolution of limestone |
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| Name an ineffective greenhouse gas |
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| Climate variations on the scale of decades may be caused by |
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| a time of abnormally low rainfall |
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| The U.S. Dust Bowl era occured when |
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| in the midwest during the 1930's |
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| What caused the Sub-Sahelian drought in Africa between 1968-1975 |
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| political instability and regional conflicts |
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| Humans produce the largest amount of CO2 by |
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Definition
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| Some effects of global warming may be |
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| increase in droughts, increase of rainfall, sea level rise, shifts in forests and agriculture patterns |
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| Earth's early atmosphere was rich in |
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| Earth's present atmosphere is rich in |
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| Climate variations on the scale of hundreds of years may be caused by |
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| changes in ocean currents |
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| Carbon dioxide has been locked up over geological time as |
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| Earth's early greenhouse climate resulted in a climate that of which planet |
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| A sedimentary rock that indicates a warm climate is |
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| The initiation of a glacial period requires |
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| polar landmasses, restricted ocean circulation, decreased greenhouse gases |
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| Three factors that added to the Late Paleocene torrid age |
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equatorial oceans, release of greenhouse gases from large volcanic eruptions, decrease in ice sheets and snow
NO LARGE METEORITE IMPACT |
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| The Late Cenozoic Ice Age began about |
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| Climate cycles with periods of about 100,000 years during the last 1 million years are probably caused by |
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| Solar radiation variation caused by orbital variations |
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International Panel on Climate Change
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| Positive Feedback Mechanisms |
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| something that results during a process that ultimately speeds up the process, or makes it continue in the direction that it is going |
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| What are the four Volcano Alert Levels |
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Green - Normal
Yellow - Advisory
Orange - Watch
Red - Warning |
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| 7 Types of Volcanic Hazards |
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Definition
Ash Fall
Lahar
Tsunami
Pyroclastic Flow
Landslide |
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| Where does most volcanism occur? |
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Definition
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All violent volcanoes associated with subduction zones.
mostly stratovolcanoes and caldera volcanoes. |
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| caused by the juan de fuca plate subducting under the continental crust of the North American plate. |
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| Signs of potential eruption |
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steam vents & high heat flow within volcano
volcanic gas concentrations increase
"young" pyroclastic and lava flow events
quakes increase and get shallower
shifting of the earth caused by magma |
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| The deadliest and most dangerous volcanic hazard |
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| failed rift, africa started to split then stopped, craters filled with water volcanic gases get trapped in the water |
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indirect result of volcanic activity, crops and agricultural systems fail.
1815 volcano tambora, 100k die from bad crops |
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greenhouse effect
natural and critical process that keeps earth's atmospheric temperature's at livable levels |
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Green House Gases
H20 - water vapor
C02 carbon dioxide
CH4 methane
N20 nitrogen oxide |
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arid, desert like conditions prevailed |
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deposits left by ancient glacieres |
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| warm, tropical, marsh or swamp conditions |
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the last 65 million years
much warmer then now, but its when the cooling trend started |
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epoch that lasted from 2 MY to 16,000 BP.
30% of earth covered in ice, present day 10%
had intervals of warming proved by expanding and retreating glaciers |
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100k year cycles that match orbital changes of the earth around the sun |
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hot spot on exposed spreading ridge, island of heimay on southern coast |
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earthflows - slow moving
mudflows - saturated, faster moving
debris flow - very fast moving |
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