Final Exam

Question 1

Landslides/Mass Wasting?

Answer 1

• Landslides occur throughout the world.
• They are most common in areas with steep slopes like mountains.
• Landslides are highly visible and ever present reminders of the dynamic nature of the Earth’s surface.
•  They also indicate how changing Earth’s surface of is as a result of constant interactions among water, air and rock.
• Landslides may not always be predictable or preventable, but knowledge of the processes and the relationship to the local geology can lead to good planning that will help reduce losses to life and property.

Question 2

What is a landslide or mass movement?

Answer 2

• Landslide same as mass wasting.
• Downslope movement of material
• Geologists use the phrase mass wasting or mass movement as the generic term
• Mass wasting or mass movement = the movement of Earth materials down slope as a result of the pull of gravity.
• Mass wasting is a natural process of the Earth’s dynamic outer layer, but human actions (which commonly involve slope modifications) can greatly increase the likelihood that mass wasting will occur.
• Mass wasting involves many different types of movement, materials, triggering events and triggering factors.

Question 3

What is the driving energy behind landslides?

Answer 3

• Gravity (The major source of energy) (it IS the driving force)
• Gravity pulls straight down – mass movement typically occurs on a slope
• The force of gravity is a vertical force that can be resolved into two vector forces:
  1.   The force vector parallel to slope that causes material to move downhill.
  2.   The force vector perpendicular to slope (~keeps material in place).
• 60% are caused by human activities
• Earthquakes are also cause them

Question 4

How do gravity and the slope work together to promote landslides?

Answer 4

-The steeper the slope the faster the material can move, mass movements are more frequent on steeper slopes
– Steeper slope yields longer slope-parallel component of gravity

Question 5

What happens to magnitude of two force vectors as slope angle increases?
-(Think back on gravity’s two vector forces)

Answer 5

• Slope parallel force gets larger
• Slope perpendicular force gets smaller
• As a slope becomes steeper the tangential (slope parallel) component increases relative to the perpendicular component and the shear stress is larger
• The steeper the slope the faster the material can move; landslides are more frequent on steeper slopes.

Question 6

What are some of the resistances to failure?

Answer 6

-Friction and the shear strength (shear strength is like papers on a slope, falling piece-by-piece) are the internal resistance of the body to movement
–Shear strength is a material’s ability to resist forces that can cause the internal structure of the material to slide against itself. Adhesives tend to have high shear strength. Fine grained sediments (e.g., mud and clay) tend to be weaker

-Shear strength is governed by factors controlled by the
–material type (hard rock vs loose sediment),
–particle shape (angular with corners vs round)
–particle size
–friction between particles (rough vs smooth outsides)
–cohesion between particles (clay vs. silica sand)
–the binding action of plant roots (plus transpiration).

-As long as the shear strength of materials is greater than the shear stress (down slope component of gravity) the particle(s) will not move, but the ratio may change with time and triggering events

-Increase the odds of landslides by steepening of the slope
–Removing support from low on slope by stream erosion, ocean wave erosion, or bulldozer

-Adding mass/weight high on a slope e.g., sediment deposition, building structures, swimming pool (IDK ABOUT THIS POINT)

Question 7

Where is there greater susceptibility?

Answer 7

• Areas with steeper slopes

- In some areas, relates to weaker (low strength) materials

Question 8

What are the types of landslides?

Answer 8

• Falls
• Topples
• Slides (includes rotational and translational)
• Lateral Spreads
• Flows

Question 9

What happens in Falls?

Answer 9

• Topples are included
• Free or rolling (tumbling) falling material
• Dominantly vertical drop
• “Scar” is site that fallen material formerly occupied

Question 10

What happens in slides?

Answer 10

• Move (slide) on top of/along a basal slip surface
• Material moves as a solid or semi-solid mass
• Some slides maintain pre-slide internal coherence
• Some slides breakup into jumble mass as they move
• Sub-types
• Rotational Slides:
  
  • CHECK PAPER WE DID IN CLASS
  • (aka slumps)
  • (thick soils/sediments, debris or earth (mud) slides)
  • Rotates on a curved failure surface
  • Head/Crown and failure scarp; toe
• Translation Slides:
  
  • (soils or bedrock ~ rock slide)
  • Slide surface is typically a plane of weakness
  • Bedding planes, faults etc.
  • Rocks slide along planar (bedding) surface

Question 11

What happens in lateral spreads?

Answer 11

• Differ from other types because they occur on nearly flat terrain
• Lateral extension of earth materials
• Operates by liquefaction (solid to liquid transition caused by disturbance of wet soils)

Question 12

What happens in flows?

Answer 12

• Earth Flows, Creep (very slow)
• Mud Flows (water-rich and rapid)
• Debris Flows/Avalanches (very rapid: fall > slide > flow)
  - Lahars are volcanic mudflow/debris flows

Question 13

Stability in slopes?

Answer 13

• Steep slopes can be quite stable when layers are inclined away from the slope of the road cut.
• Not only the layers between different rock types, but also the fracture pattern can effect this slope stability.

Question 14

Explain creep.

Answer 14

• Slow (cm/year) down slope movement of materials
• Creep is the slow downward progression of rock and soil down a low grade slope
• Mostly soil (plus plants, fence posts, buildings) but includes uppermost bedrock
• Creep mechanisms: Soils/loose sediments expand and shrink over time, due to
  
  • water in pore spaces freezes (expands ~9%) and thaws (shrinks)
  • expansion clays (expands when wet; shrinks when dry)
  • solar heating and thermal expansion
• Expansion and shrinking move materials down slope
• If temperature drops, volume shrinks
• If temperature increases, volume increases

Question 15

What are internal causes of landslide failure?

Answer 15

• Water
• Role of water can be to increase or decrease likelihood of landsliding
• WATER IS COMMONLY PRESENT within rocks and materials near the earth’s surface. It can act to either increase or decrease the likelihood of mass wasting.
• Loading - increase in likelihood
• Adding water from rain or snowmelt increases the weight or load of the rock or sediment by filling pores; it weighs more than air so mass is heavier
• This loading causes many mass movements to occur during or shortly after a prolonged rainfall.
• Increase in water pressure (aka – pore fluid pressure) - increase in likelihood
• If the voids along a surface separating two rock masses are filled with water and the water is under pressure, a buoying effect may result.
• i.e., the water pressure may be high enough to support the weight of the overlying rock mass thereby reducing the friction along the points of contact. The result can be a sudden failure.
• An analogous situation can make driving in a heavy rainstorm extremely dangerous.

Question 16

How does water both increase and decrease the likelihood of landslides?

Answer 16

• The amount of water can either increase or decrease the strength of the rock or sediment by reducing or increasing cohesion among particles.
• e.g., particles like dry sand when piled up or poured out will form a cone-shaped mound. The steepness of the cones sides, called the angle of repose, is determined by the characteristic of the material, mostly the size and angularity of the grains.
• Sand tends to pile to 32-34 degrees. Add a little water and the angle of repose is greater. Like making a sand castle.
• However, the addition of too much water saturates the sand, the spaces fill with water and the sand grains loose contact with each other, becomes a slurry.

Question 17

What is material strength? How does it contribute to or resist landslides? Which types of materials are weak and strong?

Answer 17

-Strength measures the resistance of a material to failure, given by the applied stress (or load per unit area)

• Stronger the material strength (which is determined by weathering) the less likely a landslide will occur, or at least less dangerous
• Weaker the material, the greater the landslide
• Inherently weak materials: clay minerals(can be of cliff) and sand (of hill)
• Inherently strong materials: Rock
• They form during chemical weathering of rocks
• Influenced by weathering

Question 18

Weathering

Answer 18

• Physical/Mechanical
• Chemical
• Exfoliation - cracks develop parallel to the surface, a consequence of the reduc>on in pressure during uplift and erosion (connected with chemical weathering probably)

Question 19

Physical/Mechanical Weathering

Answer 19

-Can be caused by the effects of changing temperature on rocks, causing the rock to break apart. The process is some>mes assisted by water.

• Two main types:
  1) Freeze-thaw occurs when water seeps into cracks, freezes and expands, repeats, eventually breaking the rock apart.

2) Exfoliation - cracks develop parallel to the surface, a consequence of the reduc>on in pressure during uplift and erosion

Question 20

Chemical Weathering

Answer 20

• Any of various processes that cause exposed rock to undergo chemical decomposition, changing the chemical and mineralogical composition of the rock.
• A compositional change in the minerals that make up a rock due to reaction agents.
• Major agents are oxygen, water, carbon dioxide and organic acids from decaying plants.
• These agents cause chemical reactions which change what a rock is made up of and commonly weaken the material.
• Chemical weathering occurs when rust forms on a pipe or your car.
• When chemical weathering changes the rock’s composition it also usually changes the rock’s appearance and strength. Changes color, density, hardness among other things

Question 21

Three major chemical weathering processes?

Answer 21

Oxidation

Hydrolysis

Solution

Question 22

Explain Oxidation.

Answer 22

• Also, actually the process of rusting

- Oxygen and water react with the minerals in a rock

Question 23

Explain Hydrolysis.

Answer 23

-The chemical breakdown of a compound due to reaction with water. (online definition)
H2O (water) is a unique molecule or compound. In the molecule the + charges (H) lie to one side and the – charges (O) lie to another side, a polar molecule, but the overall molecule is neutral. So, it attaches to things because of the charge and dissolves the mineral by carrying away tiny parts.

Question 24

Explain Solution.

Answer 24

-In this process CO2 combines with water to form carbonic acid. Over time this weak acid dissolves rocks, especially limestone.

–Limestone is a rock that forms mostly in the oceans, but also in lakes. It is made of calcium carbonate, and it can dissolve with vinegar, any acid.

Question 25

What are five common earthquake triggers?

Answer 25

They relate to prediction: no triggers = no landslide (for the most part)

Earthquakes and other shocks

Volcanic eruptions

Slope modifications and undercutting

Overloading

Changes in hydrologic characteristics

Question 26

Earthquakes and Other Shocks

Answer 26

• An explosion, an earthquake, a blast, electrical storm or even a truck passing by can increase shear stress and contribute to slope failure.
• The associated intense shaking can increase the water pressure along surfaces or in pore spaces and lead to reduced friction or liquefaction.
• The shaking can cause the grains to lose contact with each other reducing friction, causing liquefaction and abrupt slope failure. Any structures on or in their path are destroyed.
• A moderate sized earthquake by itself might not trigger mass movement but could do so in an area of heavily fractured rocks where the fractures are tilted downhill

Question 27

Volcanic Eruptions

Answer 27

• Volcanoes have sloped sides, and therefore, have a tangential (down slope) component of gravity.
• Materials (debris, ash and crystals, pyroclastic materials) tends to be inherently weak.
• Summit glaciers and snowfields melt during eruptions adding water to the system.
• Also lots of shaking and resultant decrease in friction in the mass.
• The high velocity (>100 km/hr) and great momentum allows these landslides to run up slopes and to cross valley divides up to several hundred meters high.

Question 28

Slope Modifications and Undercutting

Answer 28

• Slopes are modified by natural processes or human actions.
• Translational slides, especially, can occur where roads have been cut into regolith or unstable rock, creates an ar>ficial slope that exceeds the angle of repose or exposes natural planes of weakness.
• Natural over steepening by undercutting of waves or streams.

Question 29

Overloading

Answer 29

Placing a building or mass of material at the top of a slope can contribute to slope failure because of the additional weight and a steepening effect.

Question 30

Changes in Hydrologic Characteristics

Answer 30

• Rain and snow melt
• Typically subsurface water or drainage changes
• Ground may be saturated and become unstable
• A slope steepened by construction might not fail, except during a period of high precipitation.

Question 31

What are five critical aspects of prediction?

Answer 31

Slopes

Topographic Features and Vegetation

Geology and Structure

Water Buildup

Natural Triggers in Area

Question 32

How do slopes work? E.g., Does a steeper or gentler slope promote landsliding?

Answer 32

• It promotes it. The steeper the slope, the greater its potential for downslope movement.
• Construction commonly oversteepens slopes

– relates to selecting a home location

-If the artificial slopes are not protected, mass movement will occur.

Question 33

What features of vegetation and topography can indicate that a past landslide happened in a location? How do topographic features and vegetation “work”?

Answer 33

• The material on and below a steep slope should be examined prior to construction to check for evidence of landslides
• the scarp is a key
• hummocky topography is a key
• distinctly different ages of vegetation on either sides are a clue.
• also look for the turned / twisted up trees and vegetation
• tilting of recent power poles or fence posts
• road surfaces with cracks and fractures the continue off the road.

Question 34

How do changes in geology and structure characteristics relate to landslides?How does geology and structure “work”?

Answer 34

Soluble rocks, like limestone, and weak rocks, like mudstone, have a greater potential for sliding. The potential is increased if layers (bedding) or joints or other fractures are inclined downslope – toward valleys.

Question 35

How do changes in hydrologic characteristics relate to landslides? How does water buildup “work”?

Answer 35

• If surface materials on slope are wet, then failure could occur.
• How to determine without expensive drilling? Springs on the slope, areas of wet ground, pools of standing water = high water saturation

Question 36

How do natural triggers in an area “work”? How do they affect landslides?

Answer 36

-Earthquakes, volcano in the area, usually high rainfall or fast snowmelt, etc.

Question 37

Why is not building in potential landslide areas a good mitigation technique?

Answer 37

• So that people are not hurt in case a landslide does occur
• Where there is no building, people will not go
• From slide: don’t build in areas of previous slides or hazardous areas, but can’t always do so restrict usage - park not irrigated farm on top of a susceptible cliff, etc.

Question 38

What are components of a landslide early warning system and in what situations do they work?

Answer 38

• Look at picture in phone to see components of the system

- Mostly work where mass movement is triggered by rain.

Question 39

How are potential landslides monitored?

Answer 39

LiDAR is an “acronym” for Light Detection and Ranging. Using a narrow laser beam to probe through dense ground cover, such as trees, LiDAR can produce accurate terrain maps even where forest cover gets in the way of traditional photography. The technique produces a very accurate Digital Elevation Model map (DEM).

Question 40

How is drainage improved in potential landslide areas? Why is that important?

Answer 40

• Reduce water build up in slopes through engineering techniques.
• Use perforated pipe in the slope to allow water to flow away quickly and easily.
• Pump wells and empty water elsewhere.
• Important because: use a drain system to have rain by pass slope, so landslide is less likely or less effective
• Drains are usually combined with other measures such as anchors and soil removal.
• Look at picture in phone

Question 41

What are other techniques used to prevent or minimize landslide damage?

Answer 41

• (Aside from don’t build in potential landslide areas, early warning systems, and improved drainage)
• Slope Reduction: Grade into gentler slopes to reduce mass movement danger; If room is not available for extensive grading can terrace or bench (ENTER AND INDENT)–Stair steps improve stability and stop sliding materials; also prevents water erosion.
• Protect surface from rain and snow: Seal crevices, and add layers of concrete and crushed rock 8-10 cm thick; shotcrete.
• Retaining walls: Good for sediment or loosely consolidated rock; Many different materials are used, but if blocks must be interconnected – typically with rod or rebar going through them; Best to include drains, so fluid pressure doesn’t build up behind the wall
• Add vegetation
• Rock Bolts: Good for inclined layers; Holes drilled into rock below the slip surface, steel rods placed into them and concreted in; Can see along road to Hoover Dam
• Cable nets and wire fences
• Intercept ditches and berms
• Rock sheds and tunnels: Allow mass to move over or past the area
• Remote sensing and other tools that show features of landslide activity

Question 42

What are key elements in landslide preparedness BEFORE it happens?

Answer 42

AT ALL TIMES: Education – understand that landslides are possible if you live near steep hills (small or large)

• Learn whether debris flows have occurred in your area by contacting local officials, emergency management officials, state geological surveys or departments of natural resources, and university departments of geology.
• Slopes where debris flows have occurred in the past are likely to experience them in the future.
• Rockfalls occur in our area (Vegas). Debris flows commonly accompany flash floods.
• Support local efforts to develop and enforce land-use and building ordinances that regulate construction in areas susceptible to landslides.
• Buildings should be located away from steep slopes, streams and rivers, intermi”ent-stream channels, and the mouths of mountain channels.
• Watch the patterns of stormwater drainage and locations of large boulders on slopes near your home and note especially the places where runoff water converges, increasing flow over soil-covered slopes. Watch the hillsides around your home for any signs of land movement.
• Learn about the emergency-response and evacuation plans for your area and develop your own emergency plans for your family and business.

Question 43

Features that might be noticed before major landslides?

Answer 43

• Springs, seeps, or saturated ground in areas that have not typically been wet before
• New cracks or unusual bulges in the ground, street pavements or sidewalks
• Soil moving away from foundations
• Ancillary structures such as decks and patios tilting and/or moving relative to the main house
• Tilting or cracking of concrete floors and foundations
• Broken water lines and other underground utilities
• Leaning telephone poles, trees, retaining walls or fences
• Offset fence lines
• Sunken or down-dropped road beds
• Sudden decrease in creek water levels though rain’s still falling or just recently stopped. -Sticking doors and windows, and visible open spaces indicating jambs and frames out of plumb

Question 44

What are key elements in landslide preparedness WHILE it happens?

Answer 44

• Stay alert and stay awake! Many debris-flow fatalities occur when people are sleeping. Listen to a radio for warnings of intense rainfall. Be aware that intense short bursts of rain may be particularly dangerous, especially after longer periods of heavy rainfall and damp weather.
• If you are in an area susceptible to landslides, consider leaving if it is safe to do so. Remember that travel during an intense storm is hazardous.
• Listen for any unusual sounds that might indicate moving debris, such as trees cracking or boulders knocking together. A trickle of flowing or falling mud or debris may precede larger flows.
• If you are near a stream or channel, be alert for any sudden increase or decrease in water flow and for a change from clear to muddy water. Such changes may indicate debris-flow activity upstream, so be prepared to move quickly. Don’t delay! Save yourself, not your belongings.
• Be especially alert when driving. Embankments along roadsides are particularly susceptible to landslides. Watch the road for collapsed pavement, mud, fallen rocks, and other indications of possible debris flows.

Question 45

What are key elements in landslide preparedness AFTER it happens?

Answer 45

• It is best to stay away from the slide area, as there may be danger of additional slides; however, this is not always possible or desirable. Check for injured and trapped persons near the slide area. Give first aid if trained, and call for help.
• Remember to help your neighbors who may require special assistance— infants, elderly people, and people with disabilities.
• Listen to a ba”ery-operated radio or television for the latest emergency information.
• Remember that flooding may occur aCer a mudflow or a landslide.
• Check for damaged utility lines. Report any damage to the utility company.
• Check the building foundation, chimney, and surrounding land for damage.
• Replant damaged ground as soon as possible because erosion caused by loss of ground cover can lead to flash flooding.
• Seek the advice of geotechnical expert for evaluating landslide hazards or designing corrective techniques to reduce landslide risk Homeowner

Question 46

What to do if you suspect imminent landslide danger?

Answer 46

• Evacuate, if possible
• Contact your local fire, police, or public works department
• Inform affected neighbors

Question 47

Where in a hurricane is the wind the strongest?

Answer 47

• Right side of the storm because the propagation of the hurricane also contributes to its winds.
• “Right side of the storm” is defined with respect to the storm’s motion: if the hurricane is moving to the west, the right side would be to the north of the storm; if the hurricane is moving to the north, the right side would be to the east of the storm, etc.
• Eye of the storm is the most dangerous area though

Question 48

What are the main ingredients needed to form a hurricane?

Answer 48

• Apre-existing weather disturbance (e.g., thunderstorm),
• Warm tropical oceans,
• the temperature of the water at the ocean surface needs to be at least 80°F
• Moisture, and
• Relatively light winds aloft
• If the proper conditions last long enough, they can combine to produce the violent winds, incredible waves, torrential rains, and floods that we associate with tropical cyclones / hurricanes.

Question 49

How do hurricane paths over the Atlantic vary during the hurricane season?

Answer 49

-In the Atlantic Ocean, easterly trade winds steer them to the west

Question 50

How does the Bermuda High impact hurricane paths?

Answer 50

-The Bermuda High, a semi-permanent high pressure area over Bermuda in summer and fall that steers many storm systems westward across the Atlantic, has a major effect on Hurricane paths.

Question 51

Describe a Cape Verde-type hurricane.

Answer 51

• Most common type of hurricane to strike eastern North America
• Initiate south of ~30oN latitude
• Begin as storms in western Sahel region in Africa
• Travel west on the northeast trade winds
• If atmospheric conditions are favorable (minimal wind shear, low Saharan dust, moist air mass), these thunderstorm complexes eventually evolve into tropical cyclones.
• Build strength over warm far eastern Atlantic ocean (near Cape Verde Islands)

Question 52

Describe a Caribbean and Gulf of Mexico-type hurricane.

Answer 52

• Hurricanes that form in the Caribbean/Gulf
• During the early and late stages of hurricane season, which runs from June 1 through November 30, storms are typically less numerous and are more likely to originate in the Caribbean or Gulf of Mexico.
• Formed by the Intertropical Convergence Zone
• ICZ = winds from the northern and southern hemisphere, trade winds converge
• Convergence creates low pressure areas&raquo_space;> tropical storms
• ICZ moves with seasons (earth’s tilt); at Caribbean latitudes in autumn

Question 53

What are the six types of hurricane hazards?

Answer 53

• Wind
• Wind-borne debris
• Tornadoes
• Storm Surges and Flooding
• Heavy Rains and Flooding
  
  • Such storms contain much moisture and can produce major precipitation events, sometime far inland
  • Rains produce river flooding and urban flooding

-Mudflows and Landslides

Question 54

What is the cause of storm surge and how does it work?

Answer 54

• Storm surge, along with winds and rain cause most damage
• Storm surge is an offshore rise of water associated with a low pressure weather system, like tropical cyclones.
• Storm surges are caused mostly by high winds pushing on the ocean’s surface that cause water to pile up higher than the ordinary sea level
• They are not considered tsunamis because different things cause them (strong with from hurricane for storm surge vs. earthquake for tsunami)

Question 55

What type of mitigation is particularly important in hurricanes?

Answer 55

1. EVACUATION (is most important) - continued
   - Take your disaster preparedness kit with you Disaster Shelter in a box
2. Construction improvements – better roofs, better connections between roofs and building, stilts a bit of an option.
   - Hurricane straps, clips and anchor bolts may be required to get hurricane insurance
3. Prohibit building very near the coast.

Question 56

What is the purpose of contralanes and how do they work?

Answer 56

• Everyone gets out (still slow though), no one gets in

- A lane in which traffic flows in the opposite direction of the surrounding lanes

Question 57

Hurricane Season?

Answer 57

• June to November
• Between 80 and 100 tropical storms develop each year around the world. Many of them die out before they can grow too strong. 40 to 50 storms intensify to hurricane levels.
• Atlantic - Caribbean Sea - Gulf of Mexico
• The Atlantic hurricane season runs from June 1st through November 30th.
• Eastern Pacific (East of 140°W)
• The Eastern Pacific hurricane season runs from May 15th through November 30th.
• Typhoon season – mostly May - June and October - December, but can run all year
• Hurricanes are the costliest STORMS

Question 58

Hurricane Size

Answer 58

• Vary widely in physical size
• Some are compact, with only a few bands of wind and rain trailing behind them.
• Others are looser – the bands of wind and rain spread out over hundreds or thousands of miles
• Hurricanes not based on size, but wind velocity!

Question 59

Storms, depressions, and hurricanes

Answer 59

• A tropical depression is designated when the first appearance of a lowered pressure and organized circulation in the center of the thunderstorm complex occurs, with a sustained wind speeds below 39 mph.
• The rotation of a tropical storm is more recognizable than for a tropical depression. Most of the problems a tropical storm cause stem from heavy rainfall.
• As surface pressures continue to drop, a tropical storm becomes a hurricane when sustained wind speeds reach 64 knots (74 mph). A pronounced rotation develops around the central core.

Question 60

Hurricanes

Answer 60

• A tropical cyclone in which the maximum sustained surface wind (using the U.S. 1-minute average) is 64 knots (74 mph or 119 km/hr) or more.
• A cyclone is a large, atmospheric wind-and pressure system characterized by low pressure at its center and by circular wind motion, counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere due to Coriolis effect.
• The term hurricane is used for Northern Hemisphere tropical cyclones east of the International Dateline. The term typhoon is used for Pacific tropical cyclones north of the Equator west of the International Dateline.

Question 61

Coriolis Effect

Answer 61

An apparent deflection of moving objects when the motion is described relative to a rotating reference frame, like the earth. In a reference frame with clockwise rotation, the deflection is to the left of the motion of the object; in one with counter-clockwise rotation, the deflection is to the right

Question 62

Hurricanes Explained

Answer 62

• Hurricanes convert heat energy from the ocean into winds and waves – so heat/sun is the drive
• Relates to transfer of heat from topics to mid latitudes
• Tropical cyclones use warm, moist air as fuel, so they form only over warm ocean waters near the equator
• Heat energy is transferred from tropics to mid latitudes because of wind patterns
• When ocean surface is warmed to at least 80oF, the warm, moist air above it rises upward from near the surface.
• As the warm air rises, an area of lower air pressure forms below.
• Air from surrounding areas with higher air pressure pushes in to the low pressure area. Then this inflowing air becomes warm and moist and rises, too.
• The warm air continues to rise, and surrounding air swirls in to take its place.
• As the warmed, moist air rises and cools off, the water in the air forms clouds.
• The whole system of clouds and wind spins and grows, fed by the ocean’s heat and water evaporating from the surface.
• Stop or slow when they reach land because heat is lost.
• Tropical cyclones are “warm core” storm systems, powered by energy from condensation of high moisture air, which condenses at higher altitudes.
• Characterized by the release of latent heat of condensation of moist air. n  A gigantic vertical heat engine powered by Earth’s gravity, rotation and condensation. This system sustains itself until the energy supply is stopped.
• Condensation creates higher wind speeds, which pushes the cycle of storm to continue in a positive feedback loop. Once cyclones reach land, or even when they reach cold water, they typically dissipate because they lack the condensation needed to continue

Question 63

Hurricane vs. Tropical Storm

Answer 63

• > 39 mph winds = tropical storm

- >74 mph winds = hurricane

Question 64

Water temperature and hurricane strength.

Answer 64

If a hurricane moves over warm water, it tends to get stronger but over cooler water or land, it usually gets weaker.

Question 65

Hurricane Forecasting

Answer 65

-U.S. National Weather Service and National Hurricane Center does all of forecasting

-OBSERVATIONS (data) AND ANALYSIS (quality and processing of data)
Satellites
Buoys and ships at sea
Land based weather stations including islands outboard of major landmasses
Reconnaissance aircraft (very brave people flying into hurricanes)
Radiosonde – instrument packet carried by weather balloons
Doppler Radar – land based, measures wind speed

-COMPUTER MODELING 
Data input to a large number of different modeling programs (different approaches to modeling storm strength and storm tracks)
Large data sets/complicated calculations = long computational time (hours per model) ¨  Model’s predictability decreases into the future
Models are updated as storm evolves

-ISSUING AND UPDATING WATCHES AND WARNINGS
Provide public and government agencies (state, local, national – FEMA for example) with predictions
Time/location of landfall
Magnitude of storm – width of storm, wind speeds, storm surge
Allows public and government agencies to make decisions about
Evacuations (general, low lying areas)
Preparing shelters or homes to ride out storm
Storm proofing buildings (e.g. cover windows) with or without evacuation

Question 66

HURRICANE PREPAREDNESS

Answer 66

-Recommended Supplies to Include in a Basic Kit:
Water, one gallon of water per person per day, for drinking and sanitation

Food, at least a three-day supply of non-perishable food

Battery-powered radio and a NOAA Weather Radio with tone alert, and extra batteries for both

Flashlight and extra batteries

First Aid kit

Whistle to signal for help

Infant formula and diapers, if you have an infant

Moist towelettes, garbage bags and plastic ties for personal sanitation

Dust mask or cotton t-shirt, to help filter the air

Plastic sheeting and duct tape to shelter-in-place

Wrench or pliers to turn off utilities
Can opener for food (if kit contains canned food).

• Clothing
• Medicine
• Important documents

Question 67

What is a tornado?

Answer 67

• A narrow, violently rotating column of air that extends from the base of a thunderstorm to the ground. (a type of storm) (“narrow” is key word to differentiate between tornado and hurricane)
• Tornadoes are the most violent of all atmospheric storms.
• Because wind is invisible, a tornado is hard to see unless it forms a condensation funnel, which is made up of water droplets, dust and debris.
• A cloud of debris can mark the location of a tornado even if a funnel is not visible.
• Consequently, a tornado looks like a rotating, funnel-shaped cloud that extends from a thunderstorm to the ground with whirling winds that can reach >300 miles per hour.
• Damage paths can be in excess of one mile wide and 50 miles long.
• Tornadoes can cause deaths, injuries and destroy a neighborhood in seconds
• Every state in the U.S. is at some risk from this hazard.

-Advance warning is critical for safety.
–Before a tornado hits, the wind may die down and the air may be still.
–Occasionally, tornadoes develop so rapidly that little, if any, advance warning is possible.

• Tornadoes generally occur near the trailing edge of a thunderstorm.
• Clear, sunny skies are commonly seen behind a tornado.
• # 2 killer. Heat is #1(cause 60 human deaths per year)
• They form from thunderstorms

Question 68

Clouds

Answer 68

• Cumulonimbus has anvil top and is commonly associated with tornadoes
• Part of the hydrologic cycle
• Clouds are classified according to their height above and appearance (texture) from the ground
• Cirro: curl of hair, high
• Alto: mid
• Strato: layer
• Nimbo: rain, precipitation
• Cumulo: heap

Question 69

Key features used to identify a dangerous storm?

Answer 69

• INFLOW BANDS are ragged bands of low cumulus clouds extending from the main storm tower usually to the southeast or south. The presence of inflow bands suggests storm is gathering low level air from several miles away.
• The BEAVER’S TAIL is a smooth, flat cloud band extending from the eastern edge of the rain-free base to the east or northeast. Usually skirts around the southern edge of the precipitation area. Also suggests the presence of rotation
• A WALL CLOUD is a large, localized and persistent lowering cloud formation that develops beneath the base of a cumulonimbus cloud and is attached to the rain-free base of the thunderstorm. Usually is to the rear of the visible precipitation area. (It’s a tornado in baby stage).
  - A wall cloud that may produce a tornado usually exists for 10–20 minutes before a tornado appears. A wall cloud may also persistently rotate (often visibly), have strong surface winds flowing into it, and may have rapid vertical motion indicated by small cloud elements quickly rising into the rain-free base.
• As the storm intensifies, the updraft draws in low-level air from several miles around. Some low-level air is pulled into the updraft from the rain area. This rain-cooled air is very humid; the moisture in the rain-cooled air quickly condenses below the RAIN-FREE BASE to form the wall cloud.
• The REAR FLANK DOWNDRAFT (RFD) is a downward rush of air on the back side of the storm that descends along with the tornado. The RFD looks like a “clear slot” or “bright slot” just to the rear (southwest) of the wall cloud. It can also look like curtains of rain wrapping around the cloud base circulation. The RFD causes gusty surface winds that occasionally have embedded downbursts. The rear flank downdraft is the motion in the storm that causes the hook echo feature on radar.
• A CONDENSATION FUNNEL is made up of water droplets and extends downward from the base of the thunderstorm. If it is In contact with the ground it is a tornado; otherwise it is a funnel cloud. Dust and debris beneath the condensation funnel confirm a tornado’s presence.

Question 70

Tornado Dissipation

Answer 70

• The exact manner is still debated by tornado scientists.
• Thunderstorms can kill or help tornadoes
• We do know tornadoes need a source of instability (heat, moisture, etc.) and a larger-scale property of rotation (vorticity) to keep going.
• Many processes around a thunderstorm can possibly rob the area around a tornado of either instability or vorticity.
• One is relatively cold outflow–thunderstorm-cooled air.
  - At ground level, shelf clouds and roll clouds can be seen at the leading edge of outflow boundaries.
• Storm observers have documented the demise of numerous tornadoes when the mesocyclone weakens after they become wrapped in outflow air–either from the same thunderstorm or a different one.
• In some kinds of thunderstorm outflow may help to cause tornadoes, but in other forms of outflow may kill tornadoes.
• As the RFD completely wraps around and chokes off the tornado’s air supply, the vortex begins to weaken, and become thin and rope-like. This stage may last no more than a few minutes, after which the tornado dies.
• During this stage the shape of the tornado becomes highly influenced by the winds of the parent storm, and can be blown into fantastic patterns.
• The storm contracts into a rope-like tube and, like the ice skater who pulls her arms in to spin faster, winds can increase at this point, so damage may still occur.
• As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the inflow powering it.
• Sometimes, in intense supercells, tornadoes can develop cyclically. As the first mesocyclone and associated tornado dissipate, the storm’s inflow may be concentrated into a new area closer to the center of the storm. If a new mesocyclone develops, the cycle may start again, producing one or more new tornadoes. Occasionally, the old (occluded) mesocyclone and the new mesocyclone produce a tornado at the same time.

Question 71

How long does a tornado last?

Answer 71

• Tornadoes can last from several seconds to more than an hour.
• Most tornadoes last less than 10 minutes.
• The longest-lived tornado in history is really unknown, because so many of the long-lived tornadoes reported from the early mid 1900s and before are believed to be tornado series instead.

Question 72

How do scientists, or people, determine a tornado’s strength?

Answer 72

• The most common and practical way to determine the strength of a tornado is to look at the damage it caused. From the damage, we can estimate the wind speeds.
•  An “Enhanced Fujita Scale” was implemented by the National Weather Service in 2007 to rate tornadoes in a more consistent and accurate manner.
• The scale uses letter number combinations of EF-0 to E-5
• The biggest tornado did not kill the most people. Location matters, not size.

Question 73

Describe the EF (Enhanced Fujita) scale.

Answer 73

• The scale is based on damage and wind speed is estimated from that.
• LOOK AT PICTURE
• The EF-Scale takes into account more variables than the original Fujita Scale when assigning a wind speed rating to a tornado, incorporating 28 damage indicators such as building type, structures and trees.
• For each damage indicator, 8 degrees of damage are used.
• The original F-scale did not take these details into account. The original F-Scale historical data base will not change
• Many tornadoes cannot be measured because they last for short amount of time.

Question 74

Significant Tornadoes

Answer 74

• A tornado is considered “significant” if it was rated EF2 or greater on the Enhanced Fujita scale, or at least F2 on the old Fujita scale.
• No tornado is strictly insignificant. Any tornado can kill or cause damage and some tornadoes rated at a relatively low EF in open areas probably could do greater damage if they hit an area with more structures, and thus, be rated higher.
• Some workers rate killer tornadoes of any damage rating as significant.
• Those definitions are arbitrary, mainly for parsing out more intense tornadoes in scientific research.

Question 75

What is a waterspout?

Answer 75

• A waterspout is a tornado over water; may form without supercells.
• They have a lower EF number than the most intense Great Plains tornadoes, but still can be quite dangerous.
• Although waterspouts are always tornadoes by definition, they are not officially counted in tornado records unless they hit land.
• Waterspouts are common along the southeast U. S. coast, especially off southern Florida and the Keys, but can happen over seas, bays and lakes worldwide. Waterspouts can overturn boats, damage larger ships, do significant damage when hitting land, and kill people.
• The National Weather Service commonly issues special marine warnings when waterspouts are likely or have been sighted over coastal waters, or tornado warnings when waterspouts can move onshore.

Question 76

Where are tornadoes commonly located?

Answer 76

• Tornadoes occur in many parts of the world, including Australia, Europe, Africa, Asia, and South America. New Zealand reports ~20 tornadoes per year. Two of the highest concentrations of tornadoes outside the U.S. are Argentina and Bangladesh.
• Remember that violent or killer tornadoes do happen outside the U.S. every year
• About 1,200 tornadoes hit the U.S. each year. Official tornado records only date back to 1950, so we don’t know the actual average each year before that.
• Tornado Alley is a nickname invented by the media for a broad area of relatively high tornado occurrence in the central U.S.
• Dixie Alley tends to be used for areas in the SE U.S. where tornadoes are common
• Various Tornado Alley maps look different because tornado occurrence can be measured many ways: by all tornadoes, county segments, strong and violent tornadoes only, and databases with different time periods.
• Violent or killer tornadoes happen outside Tornado Alley every year.

Question 77

The sound of a tornado?

Answer 77

• Loud rushing sound: train, water fall
• Due to wind shear Ø a change in wind speed and/or direction over a short distance.
• The sound also depends on what the tornado is hitting and the debris carried
• Current research into using sound in the warning system

Question 78

Tornado Season?

Answer 78

• Refers to the time of year the U.S. experiences the most tornadoes.
• Southern Great Plains - May into early June is common.
• Gulf Coast - earlier in the spring.
• In the northern plains and upper Midwest-June or July.
• But, tornadoes can happen in any month of the year.
• Can happen at any time, but most occur from 2–9 p.m. in Tornado Alley.

Question 79

Tornado forecasting

Answer 79

• Scientists still can’t predict/forecast them
• Current average lead-time for tornado warnings is 13 minutes
• When predicting severe weather (e.g., tornadoes) a day or two in advance, look for development of temperature and wind flow patterns in the atmosphere which can cause enough moisture, instability, lift, and wind shear for tornadic thunderstorms (the four needed ingredients).
• “How much is enough” of each of those is not a hard fast number, but varies a lot from situation to situation, and sometimes is unknown.
• A variety of weather patterns can form tornadoes; often, similar patterns may produce no severe weather at all.
• To further complicate it, the various computer models we use days in advance can have major biases and flaws when the forecaster tries to interpret them on the scale of thunderstorms
• STUDY PICTURE
• To figure out where the thunderstorms will form, we must:
  (1) find the location, strength and movement of the fronts, outflows, and other boundaries between air masses that may provide lift;

(2) figure out the moisture and temperatures, both near ground and aloft, which help storms form and stay alive in this situation;
(3) find the wind structures in the atmosphere which can make a supercell (rotation needed) and then MAY produce tornadoes;
(4) make an educated guess where the most favorable combination of ingredients will be and when; and then
(5) draw the areas on a map and send the forecast.

Question 80

What are the four ingredients necessary for a tornado to form?

Answer 80

1) Moisture
2) Instability
3) Lift
4) Wind Shear

Question 81

What is Doppler Radar and how does it help in tornado forecasting?

Answer 81

• Doppler radar: bounces a microwave signal off a desired target and analyzes how the object’s motion has changed the frequency of the returned signal. This change gives highly accurate measurements of a target’s radial velocity relative to the radar (toward or away).
• Doppler radar can detect the large rotating updraft that occurs inside a supercell, a mesocyclone.
• The radar indicates strong winds blowing toward and away from it in a way that indicates whether an intense circulation probably exists in the storm and a tornado is possible.
• Possible doesn’t mean certain, so forecasters must also depend on spotter reports and in-house analysis of the weather situation over the region containing thunderstorms, to make the best informed warning decisions.
• Doppler radar can show the precipitation in a thunderstorm (through its ability to reflect microwave energy, or reflectivity) and motion of the precipitation along the radar beam. In other words, it can measure how fast rain or hail is moving toward or away from the radar.
• From a volume scan (a series of sweeps, each tilted a little higher than the last), it can show detailed structures and movements in storms.
• The farther away from the radar a storm is, the more coarse the view, because:
• (1) The radar beam spreads out with distance, like a flashlight beam, causing small features to be missed at a distance; and
• (2) the beam shoots straight as the earth curves away from beneath – a horizon that forces the radar to miss more and more of the low and middle levels of a storm with distance.
• The National Weather Service operates a series of WSR-88D radars (the radars were deployed in 1988). Doppler radar measures both the reflectivity of clouds and the speed at which the echoes are moving towards or away from the radar (called the radial velocity). Since the size of a thunderstorm is much greater than the resolution of the radar, meteorologists can use these radial velocities to determine if a storm is rotating.

Question 82

Tornado Watch

Answer 82

• Tornadoes are possible. Prepare for severe weather. Remain alert for approaching storms. Watch the sky and stay tuned to NOAA Weather Radio, commercial radio or television for information.
• Issued by the NOAA Storm Prediction Center meteorologists who watch the weather 24/7 across the entire U.S. for weather conditions that are favorable for tornadoes. A watch can cover parts of a state or several states.

Question 83

Tornado Warning

Answer 83

• A tornado has been sighted or indicated by weather radar, and there is a serious threat to life and property to those in the path of the tornado. ACT now to find safe shelter!
• Issued by your local NOAA National Weather Service Forecast Office meteorologists who watch the weather 24/7 over a designated area. A warning can cover parts of counties or several counties in the path of danger.

Question 84

What is needed to be prepared BEFORE a tornado?

Answer 84

• Build an emergency kit and make a family communications plan.
• Listen to NOAA Weather Radio or to commercial radio or television newscasts for the latest information. In any emergency, always listen to the instructions given by local emergency management officials.
• Make sure everyone understands the siren warning system, if there’s such a system in your area. -Be alert to changing weather conditions. Look for approaching storms.
• Look for the following danger signs:
• Dark, often greenish sky
• Large hail
• A large, dark, low-lying cloud (particularly if rotating)
• Loud roar, similar to a freight train.
• If you see approaching storms or any of the danger signs, be prepared to take shelter immediately.

Question 85

What is needed to be prepared DURING a tornado?

Answer 85

• If you are under a tornado warning, seek shelter immediately!
• Many injuries associated with high winds are from flying debris, so remember to protect your head.
• Go to a pre-designated area such as a safe room, basement, storm cellar, or the lowest building level. If there is no basement, go to the center of a small interior room on the lowest level (closet, interior hallway) away from corners, windows, doors, and outside walls. In a high-rise building, go to a small interior room or hallway on the lowest floor possible.
• DO NOT STAY IN A MOBILE HOME DURING A TORNADO.
• Put on sturdy shoes.
• Do not open windows.
• If no shelter available, there is no single research-based recommendation for what last-resort action to take because many factors can affect your decision. Possible actions include:
• Varies on whether you should be in or out of a vehicle. If you are in, use your seat belt.
• Be in an area noticeably lower than the level of the roadway and cover your head with your arms and a blanket, coat or other cushion if possible.
• Avoid areas with many trees.
• Protect your head with an object or with your arms.
• Never try to outrun a tornado in urban or congested areas in a car or truck. Instead, leave the vehicle immediately for safe shelter.
• Watch out for flying debris. Flying debris from tornadoes causes most fatalities and injuries.

Question 86

What is needed to be prepared AFTER a tornado?

Answer 86

• Injury may result from the direct impact of a tornado or it may occur afterward when people walk among debris and enter damaged buildings.
• A study of injuries after a tornado in Marion, Illinois, showed that 50 percent of the tornado-related injuries were suffered during rescue attempts, cleanup and other post-tornado activities. Nearly a third of the injuries resulted from stepping on nails. Because tornadoes often damage power lines, gas lines or electrical systems, there is a risk of fire, electrocution or an explosion. Protecting yourself and your family requires promptly treating any injuries suffered during the storm and using extreme care to avoid further hazards.
• Injuries: Check for injuries. Do not attempt to move seriously injured people unless they are in immediate danger of further injury. Get medical assistance immediately. If you are trapped, try to attract attention to your location.