Natural Disasters Exam 4

USCU

volcanic activity is directly related to ______ _______

plate tectonics

what is magma?

underground rock

what is a volcano?

any place where magma reaches the surface

where do volcanoes occur at?

divergent boundaries, convergent boundaries, subduction zones, and hot spots

what 3 things matter most?

silica percentage, gas in magma, and temp

what is viscosity?

how thick a liquid is, resistance to flow

when silica goes up, what happens to viscosity?

it goes up, vise versa

what makes magma more explosive?

higher silica

what makes the explosion more violent?

the more gas trapped in the magma

what controls the gas?

viscosity and the location of the volcano

does granite have high or low silica?

high silica

does basalt have high or low silica?

low

does hot magma have high or low viscosity?

low

does cold magma have high or low viscosity?

high

what are the 3 types of volcanoes?

shield volcanoes, composite volcanoes, and cinder cone volcanoes

where do shield volcanoes form?

over ocean hot spots

shield volcanoes are the _____ and ____ dangerous volcanoes in the world

largest and least

shield volcanoes have ____ magma

basaltic (low viscosity, silica, and gas)

composite volcanoes are __ times smaller than a shield volcano

10

composite volcanoes are a combination of what?

lava flow (high silica and gas), and pyroclastic deposits (fire pieces, what comes out a volcano)

what makes the volcano steep?

pyroclastics

what makes the volcano strong?

lava

composite volcanoes are the ____ explosive and dangerous

most

where do composite volcanoes occur?

subduction zones

if composite volcanoes are on continents, where do they occur?

hot spots and divergent boundaries

what are cinder cone volcanoes made of?

pyroclastics and tephra

cinder cone volcanoes are the ______ volcanoes

smallest

cinder cone volcanoes have a long or short duration of activity?

short

what are fissure eruptions?

basaltic magma over a large area

where do fissure eruptions occur?

sides of shield volcanoes, mid-ocean ridges, and continental

thin fissures have small or large volumes flows?

small

thick fissures have small or large volumes flows?

large

lava flow is when?

magma reaches the surface

what are the types of lava flow?

basaltic, andesitic, and rhyolitic

what is basaltic lava flow?

low silica, high temp, low viscosity, and the fastest

what is andesitic lava flow?

little more silica than basaltic

what is rhyolitic lava flow?

same composition of granite, extremely high silica, and most dangerous.

volcanic ash eruptions can result in?

global climate change

ash fall can disrupt?

vegetation, respiratory and eye irritation, surface water, structural damage, jet aircraft, and climate change

fissure eruptions; ocean divergent=

very mild

shield volcanoes, ocean divergent and ocean hot spots=

mild

cinder and composite volcanoes; continent divergent=

moderate

composite volcanoes; ocean-ocean and ocean-continent subduction=

violent

composite volcanoes; ocean-continent subduction and continental hot spots=

very violent

what is the temperature of pyroclastic flow?

over 100mph with temps > 100 degrees celcius

what is poisonous gas?

carbon dioxide, carbon monoxide, and nitrogen and sulfur gases

what are lahars?

loose volcanic ash becomes saturated with water and moves down volcano

what are caldera eruptions?

extremely violent eruptions, huge amounts of ash

what are all of the volcanic hazards?

lava flow, pyroclastics, ash fall, pyroclastic flow, poisonous gas, lahars, and caldera eruptions

eruptions almost always preceded by increase in what?

earthquake activity

what is harmonic tremor?

harmonic (vibration-type) ground motion caused by underground flow of magma

how are volcanoes monitored?

seismology, ground deformation, and gas emissions

what do they look for in ground deformation?

uplift of the ground, filling of magma chamber, or increases in gases

what do they look for in gas emissions?

changes in volume and chemical composistion

how to minimize volcanic hazards?

USGS alert notification system (4 levels), and mapping hazards (land use planning and evacuation routes)

hazard mapping of the Nevado del Ruiz, Colombia volcano:

preliminary hazard map completed one month before eruption, not implemented, and no emergency response in place

eruption and lahars of the Nevado del Ruiz, Colombia volcano:

steam eruption at 3:05pm, explosive eruption at 9:08pm, pyroclastic flows melted the glaciers and formed lahars

how long did the lahars take to travel downhill of the Nevado del Ruiz, Colombia volcano?

several hours

what were the lessons learned from the Nevado del Ruiz, Colombia volcano?

-Small eruptions can generate large lahars on glacier and ice-
covered mountains
•Lahars pick up large amounts of sediments from erosion of
the valleys they travel through
•Lahars in river valleys can travel very fast and 100 km or
more

-Hazard maps are no use if they are not shared,
implemented, and if warnings are not properly issued

how was the Mt. Pinatubo, Philippines volcano monitored?

by the Philippine Institute of Volcanology and Seismology (PhilVolS), and PhilVolS called in USGS when activity increased in April 1991

were hazard maps and warning systems in place for the Mt. Pinatubo, Philippines volcano?

yes

earthquake activity of the Mt. Pinatubo, Philippines volcano

increasing earthquakes that migrate directly beneath top of volcano

ground deformation of the Mt. Pinatubo, Philippines volcano

tilting of the surface showed magma moving under the volvano

gas emissions of the Mt. Pinatubo, Philippines volcano

rapid changed in sulfur dioxide emissions

when the pyroclastic valley fill deposits were contacted with rain or groundwater, what happened?

steam explosions occurred

what was the cost damages to planes?

$100 million

what was the sulfur impacts?

20 million tons of sulfur, dropped global temps by 1 degree farahenheit from 1991-1993

what did the eruption forecast prevent?

saved 20,000 or more lives and $250 million in property damages

how many deaths were there?

300

The Ring of Fire is made mostly of ___________ volcanoes.

composite

what are ways that magma forms?

increased temp, addition of water, and decreased pressure

opening on a volcano through which lava flows

vent

small circular to oval depression on a volcano that is less than 1 km across

crater

the top of a volcano

summit

large circular to oval depression on a volcano that is more than 1 km across

caldera

the sides of a volcano

flank

Which of the following hazards had major impacts during the eruption of Mt. Pinatubo in 1991

pyroclastic flows, ash fall, lahars

whats the technical term for landslides?

mass wasting

what are landslides?

downslope movement of rock or soil under the force of gravity

what are the controlling factors for landslides?

material properties, vegetation, water, and time

what are the types of material that move in landslides?

rock, soil (loose earth material), and debris (non earth materials)

the weaker and softer material is, the more likely there will be a landslide, T or F?

True

is vegetation good for slopes?

it depends

what are the types movement of landslides?

fall, slide, slump, and flow

what are the kinds of landslides?

falls, transitional slides, slumps, earth flows, and debris flows

what are Fall Landslides?

vertical movement of a rock under the force of gravity, free falling movement, and creates talus slopes

what are the most common kind of falls?

rockfalls

what are Transitional Slides?

movement of intact material along a slanted plane (a whole piece of cake sliding off a tilted plate)

what is the slowest kind of landslide?

creep

what are slumps?

rotational movement of material in one piece along a curved failure surface, material in body of slide will be rotated but otherwise unaltered

what is Earthflow?

form on hillsides in humid regions, commonly involve materials rich in clay and silt, slow

what are Debris Flows?

consist of soil, rock, and debris with a large amount of water, rapid movement, serious hazard in dry areas with heavy rains

what are primary effects of landslides?

loss of life and destruction of property

what are secondary effects of landslides?

dam rivers, cause flooding, block roads, impacting economy

how do humans increase landslides?

clearing vegetation, construction that oversteepens slopes, adds weight, adds water

how to identify potential landslides?

-crescent shaped crack on hillsides

-tongue-shapped area of bare soil on hillsides

-linear path of cleared vegetation extending down a hill

-exposed bedrock with layering parallel to slope

-large boulders at base of cliff

what does landslide prevention include?

drainage control, slope supports, grading (changing the shape of the slope), and landslide deflection

what kind of landslide was the first landslide in La Conchita, CA in 1995

slump earth flow (complex landslide- 2 landslide movement)

what kind of landslide was the second landslide in La Conchita, CA in 2005

started as an earth flow and became a debris flow

the 1995 landslide deep-seated slump-earthflow moved an estimated ___ ft in a few minutes, up to __ ft thick

200, 35