Create an account
Variables that underpin landslide classification.
mechanism of movement, type of material, amount of H2O, and rate of movement
driving and resisting forces are determined by:
type of material; slope angle and topography; climate; vegetation; water; time
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
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
occurs when the voltage gradient within a cloud or between clouds overcomes the electrical resistance of the air.
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
occurs when a large number of fast-moving electrons accumulate in a small volume and the release energy
a channel of ionized air that approaches teh ground in a series of nearly invisible bursts
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
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
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
air mass thunderstorm
short-lived storms that stop themselves by creating downdrafts that cut off the supply of mositure into the clouds
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
precipitation begins to fall, downdrafts form in areas of intense precipitation, precipitation lightning and thunder are most intense
when downdrafts occupy the entire base the supply of water vapor is cut off, precipitation diminishes, sky begins to clear
conditions necessary for a severe thunderstorm
wind shear, high water vapor content in lower troposphere, trigger uplift, potential instability
caused by a gust front lifting warm air, formed above the gust front and ahead of the main portion of thunderstorm
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
a violently rotating funnel-shaped column of air extending downward from a severe thunderstorm to the ground
an area on the flank of a supercell storm characterized by rotating clouds, precede tornado formation
a localized wall of condensed water vapor at the base of a severe thunderstorm, commonly associated with tornadoes
forms when a narrow rapidly rotating vortex emerges from the base of the wall cloud, tornado that hasn't touched the ground
small, intense, rotating wind cells that are responsible for much of the damage done by 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
steep-sided, explosive volcano formed of pyroclastic deposits and lava flows
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
a large crater produced by a violent volcanic eruoption or the collapse of the summit area of a volcano after an eruption
dense avalanches of hot gas, ash, and volcanic rock that cascade down the slopes of a volcano during an explosive eruption
dense clouds of hot gas and rock debris produced by explosive interaction of water and magma
gas, ash, and rock fragments blown horizontally from the side of the mountain at the start of an eruption; very fast and destructive
deposition of a layer of fine air-borne rock and glass that have been erupted from a volcano
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
Please allow access to your computer’s microphone to use Voice Recording.
Having trouble? Click here for help.
We can’t access your microphone!
Click the icon above to update your browser permissions and try again
Reload the page to try again!Reload
Press Cmd-0 to reset your zoom
Press Ctrl-0 to reset your zoom
It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.
Please upgrade Flash or install Chrome
to use Voice Recording.
For more help, see our troubleshooting page.
Your microphone is muted
For help fixing this issue, see this FAQ.
Star this term
You can study starred terms together