UBC EOSC 114-Midterm 2

fragments of rock that have fallen from a cliff or steep slope and accumulated at its base.
Variables that underpin landslide classification.
mechanism of movement, type of material, amount of H2O, and rate of movement
free fall and bounding of rock/blocks of sediment from the face of a cliff
downslope movement of a coherent block of rock/sediment along a failure plane
type of slide where the failure plane is curved
slow to rapid downslope movement of sediment
a very slow flow
a German term for deep-seated rock creep
pivoting of a rock mass about a point
subaqueous landslides
landslide that occurs on the floor of a lake or sea
shear strength
it resistance to failure by sliding or flow along potential slip planes
factor of safety (FS)
resisting forces/driving forces, <1=unstable slope
driving and resisting forces are determined by:
type of material; slope angle and topography; climate; vegetation; water; time
rotational slides
blocks of sediment/weak rock move along a curved rupture surface
translational slides
blocks of strong rock move along a weak plane
reasons vegetation is a factor
reduces the impact of falling rain; plant roots add strength and cohesion to slope materials; adds weight to a slope which can increase failure likelihood
reasons water is a factor
many landslides occur when slope materials become saturated; other landslides develop months/years after deep infiltration of water into a slope; erosion of the toe of a slope by a stream reduces the slopes stability.
factors that increase incidence of landslides
urbanization in landslide-prone areas; clear cutting; changing global climate increases precipitation in some areas
landslide triggers
intense rainfall, rapid snowmelt, water-level change, volcanic eruption, seismic loading, rapid erosion
indications of potentially unstable slopes
crescent shaped cracks or terraces on a hillside; a recessed crest of a valley wall; tongue-shaped area of bare soil/rock on a hillside, large piles of talus at the base of a cliff, tilted tress, pistol butt trees, exposed bedrock, tongue-shaped masses of sediment at base of a slope, hummocky land surface at the base of a slope
landslide prevention techniques
drainage control, grading, slope supports
cloud-to-cloud lightning
occurs when the voltage gradient within a cloud or between clouds overcomes the electrical resistance of the air.
sheet lightning
cloud-to-cloud lightning that is obscured by the cloud itself
cloud-to-ground lightning
occurs when the negative charges accumulate in the lower portions of the cloud and because there is a charge difference between the cloud and the ground there's lightning
runaway breakdown
occurs when a large number of fast-moving electrons accumulate in a small volume and the release energy
stepped leader
a channel of ionized air that approaches teh ground in a series of nearly invisible bursts
strokes/return stronkes
downward flow of electrons during a cloud-to-ground lightning discharge
dart leader
forms from the leftover negatively charged ions near the base of the cloud that are not neutralized by the first stroke
positive lightning stroke
winds can carry positive charges ahead of the storm, these positive charges induce negative charges at the surface resulting in lighting, very dangerous
ball lightning
appears as a round glowing mass of electrified air that seems to roll through the air or along the surface for around 15 seconds.
St. Elmo's fire
ionization in the air can cause tall objects to glow as they emit a continuous barrage of sparks
very large and short lived electrical bursts that rise from cloud tops
blue jets
upward-moving electrical ejections from the tops of the most active regions of thunderstorms
caused by the large increase in temperature during a lightning stroke which leads to the air expanding explosively and producing a noise
heat lightning
lightning that seems to occur without thunder
air mass thunderstorm stages:
cumulus stage; mature stage; dissipative stage
air mass thunderstorm
short-lived storms that stop themselves by creating downdrafts that cut off the supply of mositure into the clouds
severe thunderstorms
occur when the downdrafts actually intensify the storms
cumulus stage
unstable air begins to rise, the rising air cools to form cumulus clouds, these clouds move water vapor the the middle troposphere, the atmosphere becomes humid enough that the clouds grow vertically
mature stage
precipitation begins to fall, downdrafts form in areas of intense precipitation, precipitation lightning and thunder are most intense
dissipative stage
when downdrafts occupy the entire base the supply of water vapor is cut off, precipitation diminishes, sky begins to clear
mesoscale convective systems
clusters of thunderstorms that form from common origin
squall lines
a linear band of thunderstorms
mesoscale convective complexes
oval clusters of thunderstorms
intensely powerful storm that has a single updraft zone
conditions necessary for a severe thunderstorm
wind shear, high water vapor content in lower troposphere, trigger uplift, potential instability
outflow boundary
line seperating an air mass cooled by a thunderstorm and the surrounding air.
gust front
leading edge of strong and variable surface winds produced by downdraft
shelf cloud
caused by a gust front lifting warm air, formed above the gust front and ahead of the main portion of thunderstorm
roll cloud
caused by horizontally rotating air beneath the leading edge of the gust front
doppler radar
emits electromagnetic waves to detect the velocity of precipitation that is falling toward/away from the receiver
appear as a mall appendage attached to the body of the storm on a radar image, usually indicate tornado formation is imminent
the zone with no radar return is where the inflow of warm surface air enters the supercell
described as a boundary seperating air masses based on moisture content
a localized area of strong winds in a downdraft beneath a thunderstorm
powerful horizontal winds produced by strong downdrafts associated MCSs
downbursts with diameters <4km, dangerous for airplanes
a violently rotating funnel-shaped column of air extending downward from a severe thunderstorm to the ground
tornados spin
counterclockwise in the Northern Hemisphere (cyclonically)
tornadoes result from
large differences in atmospheric pressure over short distances
an area on the flank of a supercell storm characterized by rotating clouds, precede tornado formation
wall cloud
a localized wall of condensed water vapor at the base of a severe thunderstorm, commonly associated with tornadoes
funnel cloud
forms when a narrow rapidly rotating vortex emerges from the base of the wall cloud, tornado that hasn't touched the ground
suction vortices
small, intense, rotating wind cells that are responsible for much of the damage done by a tornado
Fujita scale
describes the intensity of a tornado
severe storm and tornado watches
an alert that weather conditions are favorable for such events; continue on life as normal while keeping an eye out
severe storm and tornado warnings
an alert that a severe thunderstorm has already developed; take immediate safety precautions
tornado outbreak
an event in which a single weather system produces at least 6 tornadoes
a rapidly rotating column of air extending down from a thunderstorm to a body of water
damaging flows of volcanic debris and water
molten rock formed deep within the Earth's crust or mantle
shield volcanoes
gently sloping, broad, convex volcano consisting of basalt lava flows
basaltic magma that erupts from volcanos
fragmented volcanic material blown out of a volcano
pyroclastic deposits
accumulations of tephra
stratovolcano/composite volcano
steep-sided, explosive volcano formed of pyroclastic deposits and lava flows
volcanic domes
volcano formed from viscous magma with a high silica content, generally explosive
cinder cones
conical volcano consisting of pyroclastic deposits, usually only erupt once or twice
a flat-bottomed, roughly circular volcanic crater produced by a single explosive eruption, commonly filled with water
huge outburst floods that are caused when subglacial volcanoes erupt and melt large quantities of ice
depressions at the tops of volcanoes that form by explosion or collapse of the summit area
steep-sided, flat toppoed volcanoes associated with glaciers
a large crater produced by a violent volcanic eruoption or the collapse of the summit area of a volcano after an eruption
volcanic vents
openings through which lava and pyroclastic debris erupt
lava flows
molten rock that flows downslope from a volcanic vent, cools, and solidifies
basaltic lava flow with a ropy surface texture
basaltic lava flow with a broken, blocky surface texture
pyroclastic flows
dense avalanches of hot gas, ash, and volcanic rock that cascade down the slopes of a volcano during an explosive eruption
pyroclastic surges
dense clouds of hot gas and rock debris produced by explosive interaction of water and magma
lateral blasts
gas, ash, and rock fragments blown horizontally from the side of the mountain at the start of an eruption; very fast and destructive
ash fall
deposition of a layer of fine air-borne rock and glass that have been erupted from a volcano
a tropical cyclone with sustained winds of at least 118km/h
a region of relatively clear skies, slowly descending air, and light winds
eye wall
the portion of a hurricane bordering the eye; it is the region with the highest winds and heaviest rainfalls
double eye walls
the presence of two eye walls; usually indicates a hurricane is achieving maximum strength
hot towers
localized portions of the eye walls that rise to greater heights than the rest of the eye wall; indicates a greater likelihood that the hurricane will intensify