Final Notes for Study Guide
Final Notes for Study Guide GEOL 110
Long Beach State
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Date Created: 05/03/16
21116 Low and High Pressure Centers Air movement can cause changes in pressure – Convergence occurs when air flows in increasing pressure – Divergence occurs when air flows out decreasing pressure • At surface, air moves from surface high pressures (H) to low pressures (L) – Air at low rises into atmosphere and then diverges in the upper atmosphere – A surface low is often associated with a high aloft and vice versa Unstable Air Tendency of air is to remain in place – Atmospheric stability – Air parcels resist movement or return to original spot after they move • In unstable air, parcels are rising until they reach air of similar temperature and density – Air is unstable when lighter, warm/ moist air is overlain by denser cold or dry air – Some air sinks and some air rises Fronts • Boundary between cooler and warmer air masses – Air masses do not mix – Warmer air will always be lifted by the colder, denser air mass – Air masses also have different humidity levels, densities, wind patterns, and stability • Different fronts – Cold front when cold air is moving into warm air – Warm front when warm air is moving into cold air – Stationary front where boundary shows little movement – Occluded front where rapidly moving cooler air overtakes another cold air mass wedging warm air in between. Hazardous Weather and Geographic Regions at Risk Severe weather refers to : – Thunderstorms – Tornadoes – Hurricanes (Chapter 10) – Blizzards – Ice storms – Mountain windstorms – Heat waves – Dust storms • Hazardous due to the energy they release and damage they are capable of causing Thunderstorms Most occur in equatorial regions – Most common in the afternoon or evening hours in spring or summer • Three conditions necessary 1.Warm and humid air available in lower atmosphere 2.Steep vertical temperature gradient such that the rising air is warmer than the air above it • Colder air over warmer, moist air 3.Updraft must force air up to the upper atmosphere • Formation – Moist air is forced upwards, cools and water vapor condenses to form cumulus clouds Stages 1. Cumulus stage • Moisture supply and updrafts continue, clouds grow • A continuous release of latent heat from condensation warms the surrounding air causing the air to rise further • Precipitation one of two mechanisms – Expanding the cloud into colder air causes water droplets to freeze;? larger snowflakes fall and melt as raindrops – Large droplets grow until they cannot be supported by updrafts 2. Mature stage • Downdrafts and falling precipitation leave the base of the cloud • Updrafts and downdrafts are present and continues to grow until it reaches the top of unstable atmosphere (tropopause) • Storm produces heavy rain, lightning and thunder, and occasionally hail 3. Dissipating stage • Upward supply of moist air is blocked by downdrafts • Thunderstorm weakens, precipitation decreases, and the cloud dissipates Cont. Types 1. Airmassthunderstorms a. – Most individual thunderstorms b. – Last less than 1 hour and do little damage 2. Severe Thunderstorms – Under right conditions, thunderstorms can be severe • Classified as severe by National Weather Service if: – Winds > 93 km (58 mi.) per hour, or : Hailstones > 1.9 cm (0.75 in), or: generates a tornado – Necessary conditions • Large changes in vertical wind shear – Greater the wind shear, the more severe the storm • High water vapor content in lower atmosphere • Updraft of air & Dry air mass above a moist air mass Cont. Severe thunderstorm types 1. Mesoscale convective systems (MCS) • Most common type • Large clusters of selfpropagating storms in which downdrafts from one cell leads to formation of another nearby –This continued growth means the storms can last for 12 hours or more 2.Squall lines Long lines of individual storm cells common along cold fronts • Updrafts form anvilshaped clouds extending ahead of the line – Downdrafts surge forward as gust front in advance of precipitation • Can also develop along drylines – Fronts with differing moisture content 3. Supercells • Upward spiraling column of air known as a mesocyclone • Smaller than MCSs and squall lines, but more damaging • Extremely violent and spawn most tornadoes • Last from 2 to 4 hour Cont. • Lightning – Common occurrence during thunderstorms • Flashes of light produced by discharge of millions of joules of electricity • Extreme heat from discharge causes air to rapidly expand – Produces thunder – Most is cloudtocloud – Cloudtoground is less common • But 25 million ground strikes in U.S each year • Complex process (simplified here) Kills about 100 and injures more than 300 each year in the United States Cont. Hail Hard, round, irregular pieces of ice originating from thunderstorms – Contain rings due to adding coatings during updrafts • Hail moves up and down in lower part of the storm adding layers of liquid water which then freezes – Cause mostly property damage • Averages 41 billion per year in the United States – Most common locations • North America: Great Plains in United States, Calgary region of Alberta, Canada • Other regions: Northcentral India, Bangladesh, Kenya, and Australia – Deaths not uncommon in Bangladesh and India because of poorly constructed dwellings Tornadoes Usually spawned by severe thunderstorms – One of nature’s most violent natural processes – 1992 to 2002, killed average of 62 people per year – Variety of shapes • Rope • Funnel • Cylinder • Wedge • Defined by vortex extending downward from the cloud and touching the ground – Called funnel clouds when it does not touch the ground • Form where there are large differences in atmospheric pressure over short distances Cont. 1. Organizational stage – Vertical wind shear causes rotation to develop within the storm – Strong updrafts in advance of the front tilt the horizontally rotating air vertically – Wall cloud rotates and funnel descends 2. Mature stage – Visible condensation funnel extends to ground – Moist air drawn upward – In stronger tornadoes, smaller whirls may develop within tornado • Suction vortices • Responsible for the greatest damage 3. Shrinking stage – Supply of warm air is reduced and tornado begins to thin • More dangerous because wind speeds increase as diameter decreases 4. Rope stage – Downdrafts cause tornado to move erratically and disappear Cont. Classification of tornadoes – Classified according to most intense damage that they produce – Assigned value on Enhanced Fujita (EF) Scale • Survey determines levels of damage experienced by 26 types of buildings, towers, and poles and hardwood and softwood trees Waterspouts • Tornadoes that form over water • Develop beneath fair weather cumulus clouds as a result of wind shear Cont. • Occurrence of tornadoes – Found throughout the world, but much more common in the United States • Has the just the right combination of weather, topography, and geographic location – Most U.S. tornadoes occur in midwestern states between Rocky Mountains and Appalachians • Spring and summer in late afternoon and evening are most common times • Highest risk is in “Tornado Alley” – stretches from north to south through the Great Plains states – Several tornado prone areas in Canada • Include Alberta, southern Ontario, and southeastern Quebec – Waterspouts • Most take place in tropical and subtropical waters Blizzards and Ice Storms • Blizzards – Severe winter storms with large amounts of falling or blowing snow, high winds, low visibilities for extended period of time • Whiteout– Extremely low visibility – Official thresholds differ • In United States: winds > 56 km (35 mi.) per hour, visibilities < 0.4 km (0.25 mi.) for at least 3 hours • In Canada: winds > 40 km (25 mi.) per hour, visibilities < 1 km (1.6 mi.) for at least 4 hours – Ground blizzard • High winds picking up previously fallen snow • Develop numerous times each winter in Antarctica, Alaska, parts of Canada, and Great Plains states Cont. Causes of blizzards – Interaction between upperlevel low pressure trough and surface low pressure – Colorado and coastal storms derived from moist ocean air – Alberta Clippers are drier with less snow and cold temperatures – Nor’easters on East Coast have hurricane force winds, heavy snows, intense precipitation, and high waves • Wind chill – Wind cools skin, evaporates moisture, reduces time it takes for frostbite to form – A reason blizzards are generally more dangerous than other snowstorms Cont. Ice storms – Prolonged periods of freezing rain • Upon contact with cold objects, rain immediately freezes to form a coating of ice – Develop during winter on the north side of a stationary or warm front – Three conditions for freezing rain 1.Ample source of moisture 2.Warm air over shallow layer of cold air 3.Objects on land close to or at freezing Fog A cloud in contact with ground Air cooling to condensation or adding water to cooled air through evaporation • Cooling – At night heat radiates from land – Warm air blows over cold water – Humid air rises up a mountain side • Evaporation – Cold air flows over warm body of water – Warm rain falls through cool air Drought Extended period of low precipitation Makes a shortage of water, food, and power Affects more people than any other natural hazards. Mountain Windstorms Develop seasonally on the downwind side of mountain ranges or glacial ice fields • Mountains block prevailing winds and can, under specific conditions, cause winds to move quickly down slopes – Chinooks, east of Rocky Mountains – Santa Ana, in Southern California • Can cause roof and tree damage, blow cars off highways, contribute to large wildfires Dust storms – Strong windstorms in which dust reduces visibility for significant amount of time – Can be several hundred kilometers in diameter and carry 100 million tons of dust – Safety hazard for travel – Affect climate and human health • Sandstorms – Desert phenomenon where sand transported in a cloud – Rarely extends > 2m (6.5 ft.) above land – Along with dust storms, occur mostly in midlatitude, semiarid, and arid regions GEOL 110 Chapter 7 Mass wasting La Conchita, Southern CA: Landslide Disaster •400,000ton landslide on January 10, 2005 –Same location as a 1995 landslide –Destroyed about 30 homes and 10 lost their lives •Study done after 1995 landslide –Showed landslides were common here –Complete stabilization would be about $150 million •Went with less costly strategies •2005 landslide showed approach was ineffectual •Still a highly desirable place to live –Property values dropped after each landslide –However, rebounded in a few years Intro. To Landslides •Mass wasting –Comprehensive term for any type of downslope movement of earth materials –Rapid downslope movement of rock or soil as a coherent mass –Include earth flows, rock falls, and avalanches •Described collectively as landslides Slope Processes •Slopes are most common landforms on Earth •All slopes are constantly evolving and materials are always in motion downslope •Slopes are composed of different segments: –High cliff or free face –Talus slope –Convex slope –Straight slope –Concave slope Types of Landslides Falling –Free fall of earth material •Sliding –Movement of material as a coherent block •Slumping: sliding along a curved surface •Soil slip: sliding along tilted surface 413 9.7 Linkages with other Hazards Shortterm events – Flooding • Slowmoving thunderstorms producing a lot of rain in a relatively short time • Stagnation of thunderstorms – storms track over the same area – Mass movements – Wildfires • Can start from lightning strikes • Longterm changes in global climate – Drought, dust/sandstorms, and heat waves • Tropical and extratropical cyclones 9.8 Natural Service Functions of Severe Weather Contribute to health of forests – Wildfires clear old growth – Windstorms topple dead trees • Source of water – Blizzards and other snowstorms, thunderstorms, and tropical storms primary source for some areas • Aesthetic value – Clouds, snow, lightning • Tourism – Tornado chasing Forecasting and Predicting Weather Hazards Timely and accurate prediction is extremely important to spare human lives – Events still difficult to forecast – Behavior is unpredictable – Doppler radar has significantly improved ability to predict paths • Detects clouds, rain, ice particles, etc. • Uses wavelength of reflected waves to determine directions • Used to make short term predictions • Can detect a mesocyclone within a thunderstorm and issue tornado warnings up to 30 minutes in advance Watches and warnings – Watch: possibility of severe weather developing – Warning: severe weather has been spotted, take action Adjustment to the severe weather Hazard Cannot prevent severe weather, but can take steps to reduce associated death and damage • Mitigation – Longterm actions to prevent or minimize death, injuries, and damage are considered mitigation – Different for each weather hazard but some general techniques • Building new structures (Example: windproofing) • Ensuring utilities can continue to function in severe weather • Warning systems • Hazard insurance Preparedness and personal adjustments Ch 10 Hurricanes and Extratropical Cyclones Hurricane Sandy •Seven days from formation to landfall –Landfall just south of New York City –Storm had swelled to largest Atlantic hurricane on record •“Superstorm Sandy” –Great size, atypical path, merged with an arctic cold front –No longer hurricaneforce winds upon landfall, but was second most expensive storm to strike the United States (after Katrina) •Damage in the United States –Triggered intense snowstorms resulting in power outages –Large waves and heavy wind and rain caused flooding and coastal erosion 10.1 Intro to Cyclones •An area or center of low pressure with rotating winds –Counterclockwise in Northern Hemisphere –Clockwise in Southern Hemisphere •Tropical or extratropical –Based on origin and core temperature •Characterized by intensity –Sustained wind speeds and lowest atmospheric temperature (cont.) •Tropical Cyclones –Form over warm tropical or subtropical ocean water (5°–20° latitude) –Have warm central cores –Tropical depressions, tropical storms, hurricanes –High winds, heavy rain, surges, and tornadoes –Derive energy from warm ocean water and latent heat •Extratropical Cyclones –Form over land or water in temperate regions (30°–70° latitude) –Associated with fronts and cool central cores –Strong windstorms, heavy rains, surges, snowstorms, blizzards –Most do not produce severe weather –Derive energy from temperature contrasts along fronts •Scientific classification and description have roots in regional names •Extratropical cyclone that moves along northward along East Coast U.S. –Hurricanes •Tropical cyclones in Atlantic and eastern Pacific Oceans –Typhoons •Tropical cyclones in Pacific Ocean west of International Dateline and north of the equator –Cyclones •Tropical cyclones in Indian Ocean SaffirSimpson Scale classifies hurricanes based on wind speed Naming Cyclones •Tropical storms and hurricanes given names established by international agreement through World Meteorological Organization –Named once winds exceed 63 km (39 mi.) per hour –Names assigned sequentially each year from list for each origin –Male/female names alternated –Names are reused every 6 years –Names of big storms are retired (example: Katrina) Tropical Cyclones cont. •Tropical disturbance –Typically 200 to 600 km (120 to 370 mi.) –A organized mass of thunderstorms persisting for > 24 hours –Associated with elongated area of low pressure (trough) –Has a weak rotation due to Coriolis effect Cont. •Tropical Depression –Tropical disturbance wind speeds increase and begins to spin –A low pressure center is formed •Tropical Storm –Winds increase to 63 km (39 mi.) per hour –Storm is given a name –Wind speeds are not at hurricane strength, but rainfall can be intense •Hurricanes –Not all tropical storms develop into hurricanes •Classified when winds reach 119 km (74 mi.) per hour –Environmental conditions •Thick layer of warm ocean water –At least 26 degrees C (~80 degrees F) –Extend to depth of 46 m (~150 ft) •Steep vertical temperature gradient –Atmosphere must cool quickly with increasing altitude •Weak vertical wind shear –Strong winds aloft prevent hurricane development Earth Materials Transported by Rivers •Rivers transport materials along with water •Total load consists of: –Bed load •Materials that roll, slide, bounce along bottom –Suspended load •Silt and clay particles that are carried in the water –Dissolved load •Materials carried as chemical solution River Velocity, Discharge, Erosion and Sediment Deposition Rivers Primary erosion. Transportation in the rock cycle Velocity controlled •Discharge –Water volume flowing through a cross section per unit time –Constant along river if no additions or deletions –Changes in area lead to changes in velocity •Crosssectional area decreases, velocity increases •Crosssectional area increases, velocity decreases •Stream flow widens and slows from high to low gradient –Forms at base an alluvial fan or delta Channel patterns and Floodplain Formation •Streams and rivers develop distinct channel patterns •Meandering Pattern Most common are meandering and braided –Curving channel bends called meanders •Migrate back and forth across the floodplain •Velocity greater on outside of curves causing erosion (cutbank) •Rivers slow on inside of curves causing deposition (point bars) –Floodplains are created during overbank flows 418 Development of Extratropical Cyclone Geographic Regions at Risk for cyclones •Most serious threat in North America –Eastern contiguous United States –Puerto Rico –Virgin Islands –U.S. territories in the Pacific Ocean •They are a lesser threat to Hawai’i and Atlantic Canada •On the Pacific coast, hurricanes strike Baja California and the west coast of the Mexican mainland Cont. •Most hurricanes that affect East and Gulf Coasts form off the western coast of Africa •They take one of three tracks 1.West toward East coast of Florida, sometimes passing over Caribbean •Move out into the Atlantic Ocean to the northeast 2.Westward over Cuba and into the Gulf of Mexico to strike the Gulf Coast 3.Westward to the Caribbean and then northeastward skirting the East Coast •May strike the continent from central Florida to New York Cont. •Northwest Pacific is much more active than North Atlantic •Indian Ocean is also a very active hurricane zone •South Atlantic and southeast Pacific, rarely have hurricanes because of cold ocean water •Hurricanes do not form close to the equator because of the absence of the Coriolis effect Hazard Greatest in Right Forward Quadrant of Atlantic Hurricanes •Local rise in sea level resulting from storm winds •Can be > 3 m (10 ft.) •Because of spinning, surge is greatest in right quadrant of storm as it makes landfall •Height is greatest near time of maximum winds •Height is also greater if landfall coincides with high tide Storm Surge •Largest effect from stress exerted by wind on water –Fetch refers to the area over which the wind blows –Larger fetch results in larger storm surge •Smaller effect from low atmospheric pressure in storm pulling up on water surface •Also depends on shape of coastline •Continual increase in sea level as storm approaches •Overwash can create washover channels, isolating one area from another Heavy Rains •Average hurricane produces trillion gallons of water each day •Rainfall from cyclones can cause inland flooding •Flooding affected by: –Storm’s speed –Land elevation over which the storm moves –Interaction with other weather systems –Amount of water in soil, streams, and lakes prior to storm Linkages and Natural Services •Coastal erosion –Some of the fastest rates during the landfall of cyclones •Some sand replaced during fairweather conditions •Other sand is removed entirely •Flooding –Saltwater from storm surge –Freshwater from heavy rains •Mass wasting –Heavy rains can cause devastating landslides and debris flows •Primary source of precipitation •Redistribute warm air from tropics •Maintain ecosystems –Winds carry plants, animals, and microorganisms –Waves stir up deeper, nutrientrich waters –Winds topple weak and diseased trees in forests –Waves break apart some corals Human Interaction with Cyclones •Human i–Population growth greatest in coastal areasdly in the past four decades –About 53 percent of United States population live in coastal counties •Urban development in coastal areas –Urbanization of vulnerable coastlines increases magnitude of the effect of cyclones –Destruction of sand dunes makes areas more susceptible to hurricane winds –Construction (increase) of seawalls and bulkheads reflect waves and contribute to beach erosion –Poor building materials and practices can make hurricanes more dangerous to people cont. •Global warming may contribute to higher intensity and frequency of hurricanes in the future –Raising temperatures of the seas surface •Possible that warmer ocean water will increase hurricane intensity –Contributing to rising sea level •Increase the reach of large waves that ride the surge Forecasts and Warnings •Cannot prevent the cyclone hazard •Enforcing building codes and evacuation procedures Need for accurately forecasts and warnings •Forecast includes: –If it will make landfall –Where and when it will strike –Wind strength –Width of affected area –Rainfall amount –Storm surge •Monitored by U.S. Hurricane Center, Canadian Hurricane Center •Hurricane watch means likely hurricane in 36 hours •Hurricane warning given when hurricane is likely within 24 hours or less Cont. •Hurricane forecasting tools –Weather satellites •Detect early warning signs •Can not show wind speed –Aircraft •U.S. Air Force, NOAA airplanes fly into the storm to collect data –Doppler radar •Give information on rainfall, wind speed, and direction of the storm –Weather buoys •Continuously record weather conditions –Computer models •Make predictions about storm tracks •Global Forecast System (GFS) model runs four times a day •Still not completely accurate in predicting storm intensity Cont. Storm Surge predictions = Time and elevation of surge Based on wind speed, fetch, ave, water depth, central pressure, forward speed Adjustment to Cyclones Hurricanes and Extratropical Cyclones •Community adjustments to cyclone hazard –Warning systems •Give public maximum possible advance notice •Media broadcasts, local use of sirens –Evacuation plans and shelters •Developed prior to hurricane season •Public transportation provided during hazard –Insurance –Building design •Withstand hurricaneforce winds •Allow passage of storm surge •Recommendations available from Partnerships for Advancing Technology in Housing (PATH) •Personal adjustments to cyclone hazard –Be aware of hurricane season –Prepare homes and property for hazard –Obtain flood insurance –Install heavy shutters that can be latched –Learn evacuation route –Make a family emergency plan –Collect emergency supplies Chapter 11 Coastal Hazards Folly Island and Submerging Coast Barrier island south of Charleston, SC Barrier to ocean waves that would strike the mainland About 10 km (~6mi) long, less than 1 km (0.6mi) wide Most of the island has an elevation of l.5.3 m (~510 ft.) Typical Atlantic Barrier Island Eroding at a high rate (proceed to the slides where 11.1 occurs to the powerpoint) 420 Waves cont. (slide 15) Variations along a coastline Irregularities in topography ocean floor and coast cause variations in wave height as it approaches shore A single wave is called a wave front Irregular Coastlines have headlands The shape of the coast is similar underwater to that of the coastline Water gets progressively shallower close to shore As the wave approaches the shore, it slows at the headland first This causes the wave front to bend around the headland (refraction) •Effects of wave refraction –Wave normals, perpendicular to wavefronts pointing toward shoreline –Wave refraction causes normal to converge and diverge –Convergence •Wave heights and energy increases •Waves are bigger here –Divergence •Wave heights and energy decreases •Breaking waves –Plunging breakers •Waves that pick up quickly •Typical on steep beaches •More erosive –Spilling breakers •Waves that spill gently •Typical on wide, flat beaches •More likely to deposit sand Beach Form and Processes •Beach consists of loose material which has accumulated by wave action on shoreline •Type of beach material depends on source of sand –White beaches from shell and coral (Pacific Islands) –Black beaches from volcanic rock (Hawaii) –Brown beaches from quartz and feldspar (Carolina) •The beach onshore –Landward extent of a beach on seashore or lakeshore •Line of sand dunes •Line of permanent vegetation or Sea cliff or bluff forms from erosion of rock or sediment –Beaches are divided into •Berm –Beach portion that slopes landward and formed by deposition of sediment by waves •Beach face –Beach portion that slopes toward water –In the swash zone where waves swash and backwash •The beach offshore –Swash zone •Zone where waves swash and backwash on the beach –Surf zone •Where turbulent waves move after waves break –Breaker zone •Where the waves become unstable, peak, and break •Longshore bar forms beneath breakers •Longshore trough forms landward from bar •Sand transport –Littoral transport •Sand movement parallel to shore •Beach drift –Sand moving in zigzag pattern in swash zone •Longshore drift –Transport of sand by longshore currents –Longshore currents •Current that flows parallel to shoreline as a result of up & back movement of water in swash zone –Updrift and downdrift •Indicate the direction in which sediment is moving or accumulating along the shore 11.3 Sea Level Change •The level of the sea is constantly changing •Relative sea level –Position of the sea at the shore –Influenced by movement of both the land and water •Eustatic sea level –Global sea level –Controlled by processes that affect overall volume of water in the ocean and shape of the basins •Eustatic sea level (global sea level) –Rises or falls when the amount of water in the world’s oceans increases or decreases –Climate/average air temperature •Temperature increases cause volume of water to expand •Temperature decreases cause contraction of water •Changes in temperature cause ice on land to melt or snowfall to increase –Volume of water in ice sheets, glaciers increases, ocean water linked –Tectonic processes •Changes ocean basin shape over long period of time •Relative sea level –Glacier melt or earthquakes can cause uplifting of land •Decrease in sea level –Rates of deposition, erosion, or subsidence makes the level rise or fall –Tides caused by gravitational pull of the moon cause daily and seasonal changes –Weather conditions •Changes in wind speed –High winds pile up water and increase water height in open water –Swell increases both water level and wave heights when it reaches the shore •Changes in atmospheric pressure –Can add a meter or more to height of storm surge Energy Behavior Temperature depends on amount of energy absorbed or reflected • Reflection depends on albedo – Describes the reflectivity of surfaces – Dark woodlands reflect 5 percent to 15 percent – Light grasslands reflect 25 percent • Absorption – Energy that is not reflected is absorbed – Different objects absorb different wavelengths – Hotter objects radiate energy more rapidly and at shorter wavelengths 9.3 Atmosphere Thin gaseous envelope that surrounds Earth – Gas molecules – Suspended particles of solid and liquid – Falling precipitation • Causes weather experienced every day • Responsible for trapping heat that keeps the Earth warm • Knowledge of structure and dynamics critical to understand severe weather Composition of the Atmosphere Composed mostly of nitrogen and oxygen – Smaller amounts of argon, water vapor, and carbon dioxide – Other trace elements and compounds • Water vapor – Important for cloud formation and circulation – Comes from evaporation off of Earth’s surface – Humidity describes amount of moisture in atmosphere at particular temperature • Relative humidity is the ratio of water vapor present to the amount that saturates the air • Increases at night because of cooler temps, decreases during the day due to heating Structure of the Atmosphere Water vapor content and temperature vary from Earth’s surface to it’s upper limits • Troposphere – All of Earth’s surface is within this layer – Upper boundary is tropopause – Temperature decreases with increasing altitude – Most visible characteristic is presence of clouds • Made from very small water droplets or ice crystals that condense from the atmosphere • Cumulus: puffy fair weather clouds • Cumulonimbus: tall, dark storm clouds – Contains most of the atmospheric carbon dioxide and methane Cloud Type Associated with Severe Weather Four aspects of atmosphere directly related to severe weather – Atmospheric pressure and circulation patterns – Vertical stability of the atmosphere – Coriolis effect (is a result of the earth's rotation. As air moves from high to low pressure in the northern hemisphere, it is deflected to the right by the Coriolis force.) – Interaction of different air masses Atmospheric Pressure and Circulation Atmospheric pressure also called barometric pressure – Weight of a column of air above a given point – Force exerted by molecules on surface • In the atmosphere, pressure decreases with increasing altitude – Nearly all of the weight of the atmosphere is in the lower atmosphere – Density and pressure decrease rapidly as you go to higher elevations Cont. Changes in air temperature and air movement are responsible for horizontal changes in pressure – Temperature influences pressure because cold air is more dense and exerts greater pressure on surface – Global variations in temperature cause global winds • At equator, air is warm and low in density – Creates low pressure zones at the equator – Air rises, condenses, forms clouds and rain – Cooler, drier air sinks at latitudes around 30° causing deserts – Similar vertical circulation cells observed at middle and high latitudes Cont. Jet streams – Midlatitude air masses of different temperatures colliding near tropopause • Westerly winds encircling the globe due to Coriolis effect • Greater the temperature difference, faster the flow Northern Hemisphere has two jet streams – Polar jet stream • Stronger of the two and boundary between cold arctic polar and warm subtropical and tropical air masses – Subtropical jet stream • Weak during the summer months but strongest in winter when temperature gradient between lowlatitude and midlatitude air masses is greatest (427) Chapter 12: Climate Change Tuvalu, South Pacific •One of the smallest nations on Earth –Located in South Pacific Ocean between Hawai’i and Australia –9 small islands, 6 are atolls –Polynesian settled the island about 2000 years ago •Highest elevation is about 4.5 m (~15 ft) above sea level –Average elevation is 1.8 m –Has experienced serious flooding in recent years during storms and high tide –Tuvalu may not be able to support its population in 50 to 100 years due to the rise in sea level 12.1 Global Change and Earth System Science: An Overview •Earth sciences –Two central goals 1.Understand how Earth works and how it has evolved from a landscape of barren rock to the complex landscape dominated by the life we see today 2.Apply that understanding to better manage our environment –Now generally recognized that human activity effects are extensive and not just local or regional –Earth system science: study of how systems are linked to affect life on Earth •The atmosphere •The oceans •The land •The biosphere 12.2 Climate and Weather •Climate refers to characteristic atmospheric conditions over a long period of time –Years or decades –Example: Pacific Northwest generally has mild temperatures, high humidity, and lots of rain •Weather refers to atmospheric conditions over short periods of time –Days or weeks –Example: Visiting Seattle for a week you may only experience bright, sunny, dry conditions Climate Zones •Temperature and precipitation simplest way to classify zones –However, it may be much more complex •Climate can be affected by processes and changes that maintain the climate system –Ocean currents –Mountain ranges –Plateaus Earth’s climate System and Natural Processes •Climate major influence on natural processes –Flooding dependent on rainfall amount and intensity –Landslides common in areas with rainy climates –Wildfires more likely in dry areas •Knowing the climate can indicate things about the hazards to expect •Climate classification supplies information about the relationship between climate and vegetation 12.3 The Atmosphere and the Cryosphere : Atmospheric Composition •Permanent gasses –Gasses whose proportions stay constant •Nitrogen and oxygen –Have little effect atmospherically •Variable gasses –Gasses whose proportions vary with time and space –Play important roles in atmospheric dynamics •Carbon dioxide, water vapor, ozone, methane, nitrous oxide, and halocarbons. •Aerosols –Particles whose proportions vary with time and space Glaciations •Cryosphere –The part of the hydrosphere where water stays frozen yearround –Permafrost, sea ice, ice caps, glaciers, and ice sheets •Glaciers flow from high areas to low areas under the weight of accumulated ice –Have budgets with inputs and outputs •New snow forms ice at high elevations •Ice melts, evaporates, and breaks off at lower elevations •Glaciers retreat and advance •Glacial intervals – Periods with major continental glaciations •Interglacial intervals –Warmer periods with less glaciations •Multiple advances and retreats of glaciers –Rare during Earth’s 4.6 billion year history –Several in the last 1 billion years –We are now living during one of those events that began 2.5 million years ago •Pleistocene Epoch –The last series of glacial and interglacial periods –Multiple ice ages –Glaciers covered 30 percent of Earth –Maximum extent 21,000 years ago –Global sea level >100 m (330 ft.) lower than today •Today –Glacial ice covers only about 10 percent of Earth –Nearly all the ice is contained in Antarctic ice sheet –In an interglacial interval •However, probably still living in a glacial event •Glacial Hazards –Glacier movement and melting have been responsible for property damage, injuries, and deaths –Hazards include: •People can fall into deep crevasses •Glacial Ice can fall from above •Can expand to overrun villages, etc •Produce an ice jam to cause flooding •Blocks of ice may fall off in avalanches •Calving produces icebergs in ocean CHAPTER 8 SUBSISTENCE AND SOILS A particular event that is an example is the subsidence aftermath of Hurricane Katrina in Louisiana. NASA investigated this particular state to investigate the soil and land from this state, and prevent and predict possible hazards. Venice is Shaking •Beautiful and famous city in Italy –Subsiding (sinking) at rate of 1.5 mm (~0.06 in) per year in some areas –Built on 118 small islands in a coastal lagoon –Extremely prone to flooding •Has been happening naturally for millions of years –However, over pumping of groundwater significantly increased rate of subsidence –Human response has been to raise buildings and streets •Frequency of floods has increased SOLUTION Mose System, which is building huge engineering barriers when there is an increase of tide Soil and Hazards •Soil –Solid earth material that has been altered such that it can support rooted plant life –Any solid earth material that can be removed without blasting Helps evaluate natural hazards •Soil is produced through weathering –Physical and chemical breakdown of rocks –Changed by residual or transported activity of soil organisms Residual/ Transported Soil and Hazards cont. •Soil development depends on: –Climate –Topography –Parent material •The rock or alluvium from which the soil is formed –Time •Age of the soil –Organic processes •Activity of soil organisms Soil Horizons •Soil profile –Created from vertical and horizontal movements –Distinct layers parallel to the surface •Layers in a profile are soil horizons –O: organic materials –A: mineral and organic materials –E: forms zone of leaching with the A layer –B: enriched in clay, iron oxides, etc., resulting from leaching •B:tenriched with clay materials •B k accumulation of calcium carbonate (kjust CaCO3), (caliche CaCO3 layers/lenses/ chunks) –C: partially altered (weathered) parent material –R: unweathered parent material HardpanImpermeable, clayCaCO3/ Iron Oxide/ Silica •Can be an important diagnostic tool for analyzing a soil profile, but can be misleading –O and A horizons are dark Soil Color Continued –E horizon is white –B horizon varies from yellowbrown to light redbrown to dark red –K horizon may be almost white •Soil color can also indicate drainage –Welldrained are aerated: red color –Poorly drained are wet: yellow color Soil Texture •Defined by proportions of sand, silt, and claysized particles –Clay: less than 0.004 mm –Silt: 0.004 to 0.074 mm –Sand: 0.074 to 2.0 mm –Gravel, cobbles or boulders: greater than 2.0 mm •Estimated in the field and refined in laboratory •Particles cling together in peds or aggregates Soil analyses help to recognize hazards (This image is used to analyze the texture of soil ) (This visual describes the description of each soil horizon ) Relative Soil Profile Development •Soils differ in development –Weakly developed soil •A horizon directly over a C horizon (without B) •Few hundred to several thousand years old –Moderately developed soil •A overlying an argillic B ttat overlies the C horizon •More than 10,000 years old (at least Pleistocene) –Welldeveloped soil •Btredder, more translocation of clay to B, andtstronger structure •Between 40,000 and several hundred thousand years and older •Soil chronosequence: youngest to oldest –Give information about the recent history of an area Water in Soils Properties of Soil •Saturated –All the pore spaces in a block of soil are completely filled with water –Unsaturated otherwise •Moisture content –Amount of water in a soil –Important to strength of soil and potential to shrink and swell •Water flow –Saturated flow if all the pores are filled with water –Unsaturated flow otherwise (more common) (this image shows the air relationships when there are solids near each other along with water ) Classifying Soils •Soil taxonomy –Used by soil scientists –Based on physical and chemical properties of soil profile Classifying Soils (cont. ) –Useful for agricultural and land use •Engineering classification of soils –Used by engineers (and for hazards) –Based on particle size or the abundance of organic material Soil Erosion as a Hazard •Can agricultural systems maintain and improve soil fertility while minimizing erosion? –Appears many practices are mining the soil –Could erode foundation of our civilization •Soil Erosion –Grainbygrain removal of mineral and organic material by wind and/or water –Removal of soil material at an unacceptable rate –Removal of soil material at a rate faster than it is being produced Cont. •Problem in urban environments –Vegetation often removed prior to development –Persists where protection is not a high priority •Rates of soil erosion –Most concerned with top, organically rich soil •Takes about 500 to 1000 years to form 50 mm (~2 in) of soil •Rate of soil for agricultural land is 0.05 to 0.1 mm per year •Accelerated erosion can remove centuries of soil in less than a decade –Rates measured as volume, mass, or weight •Amount removed from a location within a specified time and area •Can predict soil moved from original location through Universal Soil Loss Equation Introduction to Subsidence and Soil Volume Change •Subsidence –Ground failure characterized by sinking or vertical deformation of land associated with •Dissolution of rocks beneath the surface: karst topography •Thawing of frozen ground •Compaction of sediment •Earthquakes and drainage of magma •Soil volume change –Result from natural processes •Changes in water content of soil •Frost heaving –These are probably not life threatening, but is one of the most widespread and costly natural hazards Kru st •Rocks are dissolved by surface or groundwater –Evaporites: rock salt and gypsum, dissolved by water –Carbonates: limestone and dolostone and marble, dissolved by slightly acidic water •Acid comes from carbon dioxide from plant and animal decay •Common in humid climates •Rocks are dissolved and groundwater level drops, leaving behind caverns and sinkholes –Pits in that are near surface •Sinkholes in large numbers form a karst plain (This image shows a formation of Karst Topography) Krast (cont.) •Sinkholes –Vary in size from one to several hundred meters in diameter –Can open up extremely rapidly •Two Basic types –Solutional sinkholes •Acidic groundwater becomes concentrated in holes in joints and fractures in the rock •Water is drawn into a cone above the hole in the limestone –Collapse sinkholes •Develop by the collapse of material into an underground cavern 1. What happens as a tsunami is near a land? The height of the waves INCREASES due to a DECREASE in both water depth and tsunami velocity 2. Which of the following has the least relative hazard from Tsunamis? Atlantic Coast in the U.S. (ex. Florida) 3. Which is not a way a tsunami hazard can be minimized? Clearing all coastal vegetation 4. What is a problem with building seawalls to protect against a tsunami? They could lead to a false sense of security if not high enough 5. How could a community/ state/ country BEST use a runup map to prepare for a tsunami? Locate the areas most likely to be inundated to possibly move critical services outside these areas. 6. What did scientists discover about tropical ecology after the 2004 Indonesian Tsunami? Coastal mangrove forests partly protected villages from the energy of the tsunami where the waves were smaller. 7. What is a difficulty in the probabilistic approach to tsunami hazard risk? Tsunamis are generally rare events at one particular location 8. Which is the difference between a tsunami watch and a tsunami warning? Watch an earthquake that can cause a tsunami has occurred; Warning a tsunami has been detected and is spreading across the ocean towards the area 9. Even if a community is “tsunami ready”, what is still a potential problem? Education of the hazard and what to do in a watch or warning 10. When a tsunami watch or warning is issued, you can take your own personal actions. Which is NOT an action you should take? 11. How can tsunami waves be so deceiving? All the above (the trough, which is the lowest point may arrive first, They look small out of the sea due to the distance to the horizon, The time between waves may be as long as an hour, They do not break like regular ocean waves) 12. What was NOT a problem associated with the 2011 Japanese Earthquake and tsunami? Fudai Village had built a higher wall than people thought was needed in the 1960s GEOL 110 2116 Lec. 3 (CHAPTER 1 CONTINUED) Observe precursor events Events that precede a hazardous event Example: earthquakes often precede volcanic eruptions Forecast or Predict event Forecast gives certainty of event Prediction will give an estimated time for events Warning the Public Involves statements to media and public at large DATA>SCIENTISTS>PREDICTION REVIEW GROUPPREDICTION>TO THE PUBLIC AND REGIONAL OFFICIALS Risk=(probability of event) x (consequences) Consequences : damages to people, property, economic, etc. Acceptable Risk Is the amount of risk that one or society is willing to take Frequent problem : lack of reliable data for either the probability or consequences Why is this important?> to evaluate the data whether or not the information should be passed on publically or not, depending on the specific event or risk. Hazards are link to each other: Some events may cause others Ex: Hurricanes and flooding Hazards linked to earth materials Ex: Some rock types are prone to landslides or liquefaction. Increases of number of people at risk More loss of life in highly populated compared to hazardous event in a less dense area Examples: Mexico City: 10,000 killed in 1985 with 8.0 earthquake Turkey: more than 17,000 killed from 1999 earthquakes World’s population has more than tripled in past 70 year. Population grows exponentially Increases exposure to hazards, increased pollution, reduced availability of food and clean drinking water, and a greater need for waste disposal and energy resources. Impact of hazards depend on: Magnitude: Amount of energy released Frequency: Interval between occurrences Other factors: climate, geology, vegetation, population, and land use Primarily reactive approach in dealing with hazards: Search and rescue Firefighting Providing emergency food, water,and shelter Need to increase efforts to anticipate disasters and their effects (planning) Landuse planning limitations Hazard resistant construction Hazard modification control Total losses are direct losses and losses related to human actions Effects from a disaster can be: Direct (felt by fewer people): people killed or dislocated, buildings damaged, etc Indirect (affect many more people): emotional distress, donation od money or goods, taxes for recover, etc. Recovery from disaster Emergency work Restoration of services and communication lines Reconstruction Options for avoiding and minimizing effects of disasters depends on: Perception of hazards Attitudes of people to be affected Awareness Anticipatory options include: Landuse planning Insurance Evacuation Disaster preparedness Artificial control There are some benefits for hazards Examples: Flooding provides nutrients for soil Landslides create dams to create lakes Volcanoes make new land and enrich soil Global climate change is likely to change the incidence of some natural hazards Sealevel rise increases coastal erosion Deserts and semiarid regions are likely to expand Warmer ocean water is likely to increase storm activity CHAPTER 2 California straddles the boundary between 2 tectonic plates San Andreas fault: Boundary between North American and Pacific plates Los Angeles and San Francisco located on opposite sides of the fault Movement of San Andreas fault in 1906 Caused this major earthquake Earthquakes not understood at the time Scientific investigations led to identification of fault and new understanding of earthquakes San Andreas fault system Many of moderate to large earthquakes in Los Angeles on this fault Mountain topography in coastal CA result of fault Earthquakes since 1906 have cost hundreds of lives and billions of dollars in property damage Future of the Fault Los Angeles and San Francisco. will be side by side in 20 million years May be a shift in the plate boundary and a change of topography 13. Magma starts to form if rocks are close to their melting temperature and the pressure from above is decreased in the process is called Decompression melting 14. Which is NOT a sinking plate in the “Ring of Fire”? Australian 15. In order of increasing silica content, the 3 major types of magma are Basaltic, andesitic, rhyolitic 16. What is the role of drainage basin? Collect rain and other precipitation to drain into rivers or streams 17 Along the same river with no additions or deletions of flow, which situation has the greatest discharge? The discharge will be the same
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