Key terms Final Flashcards
What are telluric currents?
Variations in the earths magnetic field that induce electrical (telluric) currents.
A current in the ground or on electrically conducting networks
What is a synonym for the earth’s magnetic field?
geomagnetic field
What is a geomagnetic hazard
Extreme variations of the earth’s magnetic field can have a significant impact on technological systems
What is the earth’s internal geomagnetic field?
earth’s core
What is the external geomagnetic field?
Ionosphere and magnetosphere
What type of variations does the internal geomagnetic field have?
Slow variations
What are disturbances affecting technological systems caused by?
Disturbances affecting technological systems are caused by variations of the external geomagnetic field. Short duration (hours,days) and driven by solar activity
What is solar wind?
stream of charged particles flowing away from the sun’s corona
What are coronal hole explosions?
Occur in small localized area of the sun’s surface. Violent explosions of heat up material and shoot it in outer space.
What are coronal mass ejections?
Star scale events. Charged particles and radiation are released from the sun’s Corona in the vicinity of sunspots
What is a magnetic storm?
Temporary ( a few hours to a few days) large scale perturbation of the external geomagnetic field due to strong gusts of solar wind
What is earth’s magnetosphere?
Region around the earth shielded from the solar wind by the internal geomagnetic field
What is the interaction between the solar wind and the earth’s magnetosphere?
Charged particles from the solar wind create currents in the ionosphere, Ionospheric currents and electromagnetic induction cause variations in the external geomagnetic field and then more electromagnetic induction induce telluric currents
What is space weather?
Changing conditions in space related to solar activity
What is a meteoroid?
Extraterrestrial debris orbiting the sun
What is the primary source of extraterrestrial debris?
Most meteoroids are asteroids or fragments from asteroids
What is an asteroid?
Small rocky body orbiting the sun. Asteroid < planet
What level of hazard do asteroids from the main belt pose for earth?
relatively low impact hazard to earth
What level of risk do near earth asteroids pose?
near earth asteroids pose a higher impact hazard than main belt asteroids
What are the two types of near earth asteroids?
Apollo asteroids which cross earth’s orbit and Aten asteroids which also cross earth’s orbit)
What is a secondary source of extraterrestrial debris?
A few meteroids are fragments from comets
What is a comet?
Small object composed of ice and rock debris moving through outer space
Where are comets in relation to the sun?
Very far away from the sun. Comets: stable water ice, material dispersed too thinly for planet formation
Did Swift tuttle comet cross earth’s orbit?
It did, in an 133 year round trip
What are impactors?
Most impactors are near earth asteroids or fragments of asteroids
What is cosmic dust?
Pass through the atmosphere unchanged and settles on the surface of the earth (0.001-1mm). Amounts to ≈ 10 to the power of 5-10 to the power of 6 kg/day (planet earth is gaining weight)
What are shooting stars?
Earth is protected by its atmosphere. Shooting stars melt in the atmosphere because of friction. They blaze during ~1 second, 100 km above ground, we see the streak of hot air (approx 1mm)
What are meteorites?
Pass through the atmosphere and fall on the earth’s surface. Might split into midair fragments. During entry, exterior melts and is stripped away (Cools while reaching the surface, Often covered by black, glazed crust, Sometimes thumb-print texture due to atmospheric turbulence)
What are the two different definitions of a meteorite?
1) meteoroid between 1mm and 100m in diameter
2) impactor that has hit the ground (meteorite)
What are asteroids
diameter > 100m. Not slowed down by the atmosphere and explode on contact with earth’s surface
What are the two definitions of asteroids
1) small rocky body orbiting the sun
2) impactor larger than 100m in diameter
What was important about Chelyabinsk, Siberia?
Massive firebal in the sky and impact. Powerful shock wave (1500 people injured mostly from shattered glass
What was important about Tunguska, Siberia?
No crater
How old is planet earth?
4.6 billion years (Ga)
What is the time unit used in geology?
1 million year (Ma)
What is important to know about the K/Pg boundary event?
Impact of global consequences (extinction) related to this impact
What is one of the causes of the extinction from the K/Pg event?
Stress on life from extensive volcanism in Decca
What scale is used to evaluate impact hazard?
The torino impact hazard scale
What is the typical diameter of a crater?
Crater diameter ~ 20x impactor diameter. Craters with diameter > 5km do not contain meteorites
What are some distinctive features of impact craters?
1) circular feature
2) crater is steep sided and closed
3) rim rocks are titled away from the crater
4) shattered rocks on the crater floor
5. large angular blocks of rock scattered around crater
6) presence of meteorite fragments
7) shock minerals (indicative of extreme T and pressure)
8) shatter cones
9) melted rock due to impact
What is a shatter cone?
A conical fragment of host rock fractured by the shock wave generated by the impact
Core features of Simple vs. Complex crater
Simple crater: Small impactor, diameter < 5km
Complex crater: large impactor, diameter > 5km
What is the most important way that gravity varies at different locations on the surface of the earth?
Heterogeneities in the subsurface
What is the instrument used to make gravity measurements in the field called?
a gravimeter
What is mass movement?
Collective name for a variety of processes for the downslope movement of earth materials under the direct influence of gravity
What is the driving force?
is the component of gravity parallel to the slope
What is the resisting force?
is proportional to inertia and friction and counteracts the driving force
What is friction?
force that resists motion between two surfaces in contact
What are the controlling factors of friction?
Surface roughness of the surfaces and presence of lubricants
What are the friction coefficients
mu=0.3, brick on moist clay is less stable
mu=0.5 brick on dry clay
mu=0.6 granite on granite more stable
What is Congelifraction?
Disintegration of a rock due to several cycles of water freezing and melting
What percentage do silicon and oxygen account for in the crust?
~75%
What is a silicate?
Group of minerals containing Si and O combined with other elements. Most abundant mineral group in the earth’s crust
What is clay?
General term which describe a variety of complex sheet silicates. Structure is a stack of thin sheets, sheet surface is negatively charged. Attracts water molecules and positively charged ions
Water is a bipolar molecule with a positive and negative side, describe positive and negative side
Positive side of water molecules attracted by negative charges on the surface of clay sheets
What binds the clay in a flocculated structure?
Salt binds the clay sheets and silt together
What type of rocks do mass movements occur in most frequently?
They occur in all three types but most often in sedimentary rocks
What are the particle sizes or rock, debris and earth?
Rock is the largest, then debris (coarse soil particles) and then earth (fine soil particles)
What are falls?
Rapid, free-fall mass movement. A bouncing rolling end over end motion. Fragments ranging in size from small grains to large blocks. They develop in material weakened by fractures
What is a slide?
Mass movement involving motion along a failure surface. Material remains as a block (preslide coherence maintained) and failure surface is well defined
What are lateral spreads?
Special case of translational slide in which movement of earth material results from liquefaction of subjacent material. Related to distinct geological conditions present in northern environments
What is liquefaction?
Phenomenon in which the strength of soil is reduced by rapid and violent shaking or loading. Occurs in saturated soils in which the space between particles is filled with water.
What are the 4 steps of lateral spreads?
1) marine calys deposited in glacial regions. Salt is present due to the sea water leading to flocculated structure
2) Glaciers melt. the earths surface is uplifted. Clays are above water level
3) clays are leached by fresh water from rain and snowmelt (salt removed)
4) clays instantly change to dispersed structure (liquefaction)
In a Marine environment clay is ____ because of ______ water whereas above sea level clay is ____ because of ____ water
Salt and Strong
weak and fresh
in a lateral spread, what is the failure like?
It is retrogressive, often starts on a river bank and proceeds rapidly inland
When glacier first melted in the ottawa area, there was up to 100m of what kind of clay and silt?
Marine clay and silt (leda clays) deposited
What are rotational slides?
Slide in which failure occurs on a very steep slope, along a concave rupture. Multiple blocks often fail and due to natural factors (e.g., wave erosion) or human activity (e.g., road cuts)
What are flows?
Mass movement involving continuous internal deformation of the moving material.
What is the main difference between slides and flows?
Slides have little deformation within the moving material whereas in flows material is thoroughly deformed during movement
What is a creep?
gradual, slow movement of earth and debris downhill
How does creep work?
Expansion under wet conditions, contraction under dry conditions. Net movement is down slope
What is rock, debris and earth flows?
A mixture of rock fragments, soil and water flowing downslope as a viscous fluid.
What is gelifluction?
type of flow observed in northern regions, linked to the melting of the top layer of permafrost. Water cannot infiltrate through the permanently frozen, impermeable layer below . Soil becomes saturated and weak and flows down gentle slopes
What are complex events?
Combination of falls, slides and/or flows. Most mass movements are complex of events
What is an avalanche?
Rapid complex event
What is subsidence (slow and rapid)?
Slow subsidence: gradual sinking of the land surface.
Rapid subsidence: surface collapse of underground cavities (manmade and natural)
What are sinkholes?
Circular area of subsidence caused by collapse into subterranean void. Occur typically in sedimentary rocks that can dissolve in water. Diameter ~ tens of metres
What is a snowpack?
Is composed of several layers with different characteristics. Thickness, density, hardness, cohesion, strength etc. Formed under different weather conditions and properties can change over time.
what is cohesion?
Property of the particles of a material to stick together. Low cohesion snow is fresh “powder” snow and 95% volume is void space
What is Hoar?
Relatively large crystals formed by the deposition of water vapour into ice. Often grow on existing crystals and some hoar crystals are feather shaped
What is the level of strength of the hoar layer?
Hoar remains a relatively weak layer
What is sluff
Avalanche too small to bury a person
Which is generally more destructive, wet or dry snow?
Wet snow (speed 30-65km/h) is more destructive than dry snow (65-100km/h). Wet snow is generally more destructive because of the greater force of impact of the denser material
How are the size of avalanches ranked?
Logarithmic scale based on the mass of snow
What type of avalanche is most often associated with low cohesion snow
Point release avalanche
What type of avalanche is most often associated with cohesive snow
Slab avalanche
What kind of avalanches are the most dangerous?
The most dangerous avalanches are slab avalanches
What kind of mass movement do point release avalanches have similarities with?
Flows of earth materials
What kind of mass movement do slab avalanches have similarities with?
Slides of earth materials
What condition that decreases stability might develop between snowfalls?
In areas of low friction, there could be several potential failure surfaces. one of which is the melt-freeze crust might develop between snowfalls`
What could happen if the slope angle of the start zone is 25-50 degrees?
Infrequent, large dry slab avalanches. Recreational use
What’s a cornice?
Snow structure formed by wind loading snow on the downwind side of an obstacle, often a mountain ridge line
What kind of weather conditions trigger avalanches?
Most avalanches occur naturally during or soon after snow storms
What are hurricanes?
Tropical cyclones. Means of exporting heat from tropics to mid-latitudes. An energy conversion system
What are synonyms for hurricanes?
Hurricane (atlantic and east pacific) Cyclones (indian ocean, south pacific, Australia) Typhoons (west pacific
What is the primary energy source of hurricanes?
Ocean heat. Hurricanes gain energy as they travel over the ocean
How do hurricanes release energy
They release energy as rain
What is the pressure gradient at the eye of the hurricane?
Its a low pressure region
What is the coriolis effect
The coriolis effect refers to the impact of earth’s rotation on winds. In the NA, winds are deflected to the right when flowing towards the eye.
Explain the force body diagram of a hurricane
1) pressure gradient points to the eye
2) coriolis force
3) Centrifrugal forces pull to the right
4) Friction slows down wind
Balance of forces cause surface winds to spiral inward counter clockwise (CCW)
What are the birth ingredients for a hurricane?
1) water temp >= 27C
2) warm, humid, unstable air
3) in the northern hemisphere, surface winds rotating counterclockwise
4) significant coriolis effect to sustain rotating surface winds
5) weak high altitude winds`
What is a tropical disturbance?
Poorly organized cluster of thunderstorms. Weak surface winds (<37km/h). Diameter 200-600km. Frequent in tropical regions
What is a tropical depression?
Clearly defined low pressure central area. Organized wind circulation initiated (vertically and laterally, 37-63km/h) Depressions are numbered
What is a tropical storm?
Classical hurricane structure but no eye. Counterclockwise winds (64-118km/h). storms are named
What is a hurricane?
Classical hurricane structure with a well-developed eye. Eye forms when winds >118km/h. Hurricanes are named
What are rainbands?
dense clusters of thunderstorms spiralling slowly counterclockwise. Hurricane diameter ~500km and most intense rain fall
What are the strongest winds in the hurricane structure?
Winds spiral up along eye wall and these and these are the strongest winds
When do hurricanes decline?
Hurricanes decline rapidly after they make landfall
Where are the strongest winds in a northern hemisphere hurricane?
strongest winds on the right side
What is the hyrdologic cycle?
it describes the constant exchange water between oceans, atmosphere and continents. Energy is derived from the sun and water is a key factor in several geological processes
What processes are involved in the hydrologic cycle?
Evaporation and precipitation.Runoff and infiltration. Transpiration. Sedimentation and volcanism
What paths does water take after precipitation on land?
A portion flows across the surface into streams this is runoff. A portion soaks into the ground this is infiltration.
More _______, less flooding hazard
infiltration
What percentage of water is in rivers and streams?
0.0001% in rivers and streams
What is the drainage basin?
area of land that convey all runoff into a particular body of water
What is drainage density?
Measure of the tendency of a drainage basin to flooding. Drainage density= Length of all stream segments/area of basin
What results in low drainage density?
Small overall stream segment length. Which is a lower flooding hazard
What results in high drainage density
Long overall stream segment length and higher flooding hazard
What is discharge?
Volume of water flowing in a stream per unit time (Q= A x V)
what is load?
Sediments transported by a stream
What is channel gradient?
Slope= Δelevation / Δdistance . Higher gradient at the head and lower gradient at the mouth
What does sinuosity mean?
Having lots of curves or turns
When does flooding occur most and less often?
Flooding occurs most often due to weather conditions, discharge temporarily exceeds the capacity of a channel to contain the flow. This is called a hydrometeorological flood.
Flooding occurs less often when there is a local obstruction to flow. This is called a natural dam flood.
What is a a hydrometeorological floods?
In canada most floods are related to weather phenomena. 2 mechanisms often acting in combination: 1) abundant rains 2) spring melt. April and may particularly vulnerable
What are snowmelt runoff floods
in the spring, flooding occurs when the amount of meltwater runoff exceeds the capacity of streams to contain the flow
What are storm rainfall floods?
During torrential rains, amount and duration of precipitation exceeds infiltration capacity of the ground
What is a flash flood?
Flood that rises and falls rapidly (minutes) with little or no advance warning, usually as a result of intense rainfall over a relatively small area
What are rain-on-snow floods?
Combination of snowmelt-runoff and storm rainfall floods. Rain is augmented by melt water to generate substantial runoff
What are ice jam floods?
resulting from the temporary obstruction of river flow by ice buildup. water levels rise upstream, behind the blockage and river might overflow its banks. Coincide with spring melt and some localized areas especially prone to the formation of ice jams
What rivers are at particular risk of having an ice jam flood?
Rivers flowing from south to north
What are natural dam floods?
resulting from blockage by: mass movement, glaciers advance and retreat and lava flows
What is an outburst flood?
A type of downstream natural flood. Flooding when dam fails
What is a Jokulhalup?
outburst flood resulting from a volcanic eruption underneath a glacier (extreme discharge and short duration- a few days)
What are dams?
control discharge by holding
flood water in reservoirs and releasing it at a set rate
What are levees?
dikes that confine flood water by increasing the height of the channel
What is a floodway?
artificial channel open to waterflow at peak discharge to handle excess volume
What is climate?
meteorological elements and phenomena averaged over a long period of time for a region of the earth’s surface
Climate vs. Weather?
Climate= long term variations (30 years) weather= short term variations (a few days to years)
how does air overcome gravity
Rising air looses energy and becomes cooler. Sinking air gains energy and becomes
warmer
What are the characteristics of warm air?
Expands in volume (less dense and low pressure), rises, holds more humidity, molecules move more (unstable)
What are the characteristics of cold air?
Contracts in volume (denser, high pressure) sinks, holds less humidity, molecules move less (more stable)
What is wind?
Horizontal movement of air from regions of high pressure to regions of low pressure
What is a cyclone?
Counterclockwise surface winds, forms in low P zone, air rising (water vapour condenses into rain and upper level outflow of air)
What is an anticyclone?
Clockwise surface winds, forms in high p zone, air descending (dry and windy conditions on the ground)
What is rain accompanied by?
a large release of latent heat
What is latent heat?
energy absorbed or released during a change of state
What is a thunderstorm?
Meteorological event associated with a localized storm cell, producing thunder and lightning. Thunderstorms are composed of individual cells developing over 20-30 minutes. As one cell dies another may develop nearby
What are the 3 stages of development in a thunderstorm
1) cumulus stage
2) mature stage
3) dissipating stage
Describe the cumulus stage
Thunderstorms occur when warm and moist air is lifted upward. By mechanical lifting (cold, dense air undercuts warm, less dense air. Or bu thermal lifting (warm, less dense air flows up and over cold dense air along a gentle slope)
What type of lightning bolts are a danger to people?
Cloud to ground/ground to cloud
What is a tornado?
Funnel cloud coming out of a cumulonimbus and extending toward the ground with air spinning at high speed
What type of thunderstorm are most tornadoes associated with?
Most tornadoes are associated with supercell thunderstorms
What type of clouds are tornadoes produced within?
Most tornadoes are produced within cumulonimbus clouds during supercell thunderstorms
What are ice storms and freezing rain?
precipitation that falls in liquid form and freezes upon contact with the ground or a cold object. Precipitation reaches the ground as a
supercooled liquid. Droplets of liquid water at T<0°C. Creates a thin, smooth veneer of ice (no air bubbles)
What are the conditions for the formation of freezing rain?
Temperature hovering around T=0°C. Forecasting freezing rain is difficult. A layer of warm air sandwiched between two layers of cold air
