ESCL 2 Flashcards
assessing risk involves
(1) understanding the type(s) and extent of hazard, (2) assessing exposure and vulnerability of the potentially affected area and population, including infrastructure
and things like evacuation routes, etc., and (3) determining total potential loss/ risk based on all of these factors
mid continental earthquakes
would be more devastating becuase people are not prepared and do not expect an earthquake
earthquake risk in illinois
is actually very high
explosive volcanoes
Explosive eruptions occur where cooler, more viscous magmas (such as andesite) reach the surface. Dissolved gases cannot escape as easily, so pressure may build up until gas explosions blast rock and lava fragments into the air!
Lava flows are much more thick and sticky so do not flow downhill as easily. These eruptions build up more steeply-sloping Composite volcanoes like this one in Chile.
effusive volcanoes
Effusive eruptions occur when hot, (1200oC) runny basalt magmas reach the surface. Dissolved gases escape easily as the magma erupts, forming lava that flows downhill quite easily.
Effusive eruptions build up gently-sloping Shield Volcanoes like Hawaii.
List of Volcanic Hazards
Pyroclastic Density Currents (pyroclastic flows andsurges)Lahars.Structural Collapse: Debris flow-Avalanches.Dome Collapse and the formation of pyroclastic flows and surges.Lava flows.Tephra fall and ballistic projectiles.
Volcanic gas.Tsunamis.
subductionzone/ convergent boundary
higher viscosity with more silica slow to no movement cinder cone explosive
viscosity
ease of magma flow
divergent
lower viscosity with less silica fluid movement creates composite
geotectonic setting
formation of rock in earths crust
cinder cones
pyroclastic flow bits of violently erupted material higher viscosity mono inyo craters in california
shield volcanos
lower viscosity flows like in hawaii
`stratovolcano/ composite volcanos
are a mix with a cake like layer with both magma and gas mt fuji japan are the most dangerous
hot spot
area not at boundary will have high viscosity at land and low viscosity at sea
high silica content
high viscosity more explosive style
volatiles
trapped gases and water vaport leading to explosive eruptions
more explosive volcanoes
cause fissure eruption and lava fountain
hazard
damage
risk
people getting hurt
ocean volcanos
sea floor hot spots sea floor spreading mid ocean ridges non explosive volcanos low silica content convection of earths mantle that pushes plates and exudes magma
phreatic effects
steam explosion
lahar
wet mudflow mass of volcanic fragments stratovolcano trait
lateral blast
do not erupt at summit but on the side of volcano
glacial volcanos
flood and also phreatic effects
caldera
when large pool of magma melts mountain to a crater
active dormant extinct
currrently erupting 10,000 years ago and due will never again
Volcanic risk rating by scientists includes consideration of:
historical (oral, written, geologic) record of eruptions - size, type, etc.
evidence of prehistoric eruptions and types of eruption products
classification of volcano (current “restlessness”? i.e., earthquakes, gas emissions, ground swell/deformation, etc.)
demographics: population density, economics, potential losses (property, crops, etc.), infrastructure and vulnerability
why do people live near volcanos
fertile soil - why is this associated with volcanoes?
geothermal (hot springs and energy source)
many important mineral and rock resources – pumice, sulfur, metal ores, etc.
please note that tourism is not a geologic benefit!
also consider: “creation of new land” time scale
questions for geologic resources
what used where found how get how needed how useful what impacts
volcanic explosive index
measures amount of eject volume
