Geol 118 Final Exam
End of Mesozoic/ beginning of Cenozoic
(100 - 50 m.y.a.) - very warm interval, resulted in flooding of much land on continents (glaciers melt, sea level rises). Major reason for warming is > levels of CO2 gas (7 - 10x today's level) from > volcanism by rapid sea floor spreading associated with opening of Atlantic ocean. (Other factors = warm, deep ocean water melted ice crystals with methane trapped inside (methane gas hydrates), releasing another greenhouse gas; distribution of land + ocean masses, < reflectivity of Earth + change in ocean circulation patterns.)
River stream
- flowing water at Earth's surface usually confined to channel; water derived from rain or melted snow that runs over Earth's surface or through ground into river. Rivers flow downhill due to gravity, eroding + transporting sediment, eventually to ocean. Sediment carried by river = river's load - grains (clay through boulders) that are carried up in water (suspended load) or near bottom (bed load) by grain hopping or rolling. With > velocity, river can carry greater load and larger grains. Load also includes dissolved salts (dissolved load).
Meteorite Impacts: Origin of Earth/ Solar System (lithosphere, hydrosphere and atmosphere)
4.6 billion years ago, Earth (and solar system) formed by collisions of many meteorites (pieces of rock and metal, photo) and comets (dirty ice balls, photo).
Composition of Earth's Current Atmosphere
78% Nitrogen 21% Oxygen .9% Argon .04% CO2 <.01% Others Excludes water
Radiation
All objects emit e-m radiation, nature of which depends on their temperature. With > temperature, object emits > amount of radiation (> intensity) with shorter wavelength.
Effect on Sea Level impact on Climate Change
If current glaciers were to melt, that water (now on land) would drain into oceans, causing sea level to rise, which would result in flooding of many coastal cities. Alternatively, if glaciers were to become much larger (as in Ice Age), water from oceans gets transferred to ice on land, causing drop in sea level. During Ice Age (past 2 m.y.), glaciers covered ~1/3 area of continents, reducing sea level by ~100 m compared to today. East Coast of USA was 100 km east of NYC, France and Britain joined by land (today English Channel), and Alaska and Siberia were joined by land.
Trough
Lowest point of a wave
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Mississippi River Flood of 1993 (link #2, #3, #4, #5, #6, #7; Flood! PBS/NOVA, 12:15-30:58, 31:45-34:00) During summer of 1993, record floods plagued upper portion of Mississippi River. Worst flood disaster in history of USA (and costliest and most widespread natural disaster in history of IL) in terms of area affected, number of rivers which recorded record stage and discharge (~150 rivers involved), amount of damage, and flood duration (weeks to months). Property damage $12 - 20 billion and ~50 deaths. > 50,000 homes were seriously damaged or destroyed, 54,000 people were evacuated from home at some point. Worst hit areas were Iowa, Missouri, and Illinois. High rainfall over large area for 6 month period before flooding and then many rainstorms in June through August, including several very intense ones. Stationary front over Midwest, warm moist Gulf of Mexico air mixed with cold Canadian air. Many gaging stations measured record discharge, 46 stations recorded >100 year flood (see data for a few). Many levee failures (85% of those built by US Army Corps of Engineers held, but only 22% of those built by local communities held - ~1,000 failed levees). Damage to agricultural land (sand eroded from river channel and deposited over crops in floodplain, also massive soil erosion), impact on transportation (bridges over Miss. River were closed, Interstate highways, river barges, railroads, and airports were all closed). See 6 maps of Midwest showing damage to agriculture, commercial properties, public facilities, residential properties, transportation, and utilities. Des Moines, Iowa = largest US city to lose its water supply due to flooded water treatment plant. > 250,000 people lost drinking water for 12 hot days. Economic losses in Des Moines alone totaled ~ $716 million. Flood relief involved attempts to save levees with support from sandbags. Valmeyer and Prairie Du Rocher, IL - levee district - area (in shape of letter c) protected by single levee. Individual districts are in shape of letter c. Levee broke on upstream side, floodwaters picked up speed and overtopped next levee. Wall of water crashed into Valmeyer, causing major damage (Valmeyer has since moved out of floodplain with federal help). US Army Corps of Engineers quickly determined that onrushing floodwaters would soon overtop next levee and inundate historic town of Prairie Du Rocher. So they deliberately broke levee at southern point to send floodwaters northward and slow down onrushing water from north. ~15 minutes of video describing the compelling story of Valmeyer and Prairie Du Rocher. Valmeyer after flood. Quincy, IL - 5-mile wide floodplain that was filled, couldn't cross bridge over Mississippi River into Missouri St. Louis, MO (photo #1, #2) - protected by 52-ft high floodwall, which almost collapsed and came close to being overtopped. Grafton, IL (photo #1, #2) - town with no protection, frequent flooding, supposed to be relocated with government aid (FEMA), but didn't. Alton, IL - most of town is above floodplain, except for downtown business district, grain elevator, and water treatment plant. Alton constructed emergency levee out of sandbags (700 ft long, 9 ft high) which spared downtown area. Slides of Mississippi Flood, 1993 Red River of the North Flood, Spring 1997 (link #2, #3) Red River of North begins near where North Dakota, South Dakota and Minnesota meet and flows north, forming border between ND and MN. Eventually empties into Lake Winnipeg in Manitoba, Canada. During April of 1997, area experienced worst flood disaster for area due to heavy winter snowfall (3.5 times average), then blizzard in April (~25 cm) and quick warming caused snow melt to fill river. Frozen ground enhanced runoff and farther north, Red River was still frozen so nowhere else for floodwater to go. Floodwaters at Grand Forks, ND were ~26 ft above flood stage. Because area is so flat, large area was underwater (photos #1, #2, #3, #4, and #5). >24,000 homes in Grand Forks were partially or completely destroyed by flooding and flood-induced fire; 50,000 people were evacuated and damage = several $ billion. Link to lots of photos.
Beaches
Most dynamic environment due to continuous erosion,transport and deposition of sediment by waves or tides. Can undergo great changes in shape,location, or both during single storm or gradual continuous change due to rising sea level.
Effects of Meteorite Impact during time of the dinosaurs
Most important effects = impact sent large amounts of dust into upper atmosphere; melting of crust and asteroid; shock waves reflected upward, sending molten rock skyward, igniting global fires, and sending soot into upper atmosphere. Dust and soot in atmosphere formed thick, dark cloud that blocked out Sun around globe for months; cloud blocked photosynthesis and caused global cooling. Plants died, disrupting food chain. Dinosaurs and other organisms starved and froze to death
Coastal Processes
Most important process in coastal areas is action of waves. Lesser importance is tides.
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Problem - Many nations in world have coastal zones; 30 of our 50 states have coastlines along major water body (Atlantic + Pacific oceans, Gulf of Mexico, + Great Lakes); ~ 50% of USA population lives in coastal counties + population density >>. Coastal erosion = ongoing, gradually developed geologic hazard in USA + world. In USA, much of Atlantic + Gulf coast are severely eroding + other coasts (Pacific + Great Lakes) are moderately eroding. Housing developments lost to sea. Storms + hurricanes can cause great erosion at specific localities, but by themselves cannot account for continuous, large-scale erosion. Causes of large-scale coastal erosion (1) Global rise in sea level - sea level rose through last century by 2 - 3 mm per year due to global warming. Since 1880, sea level has risen by ~20 cm. Small rise in sea level can cause large change in position of coastlines for flat areas (USA map of coasts vulnerable to rise in sea level). Models predict >> rates of rising sea level (3 - 5 x increase) due to enhanced Greenhouse Effect. Future possibility of flooding of major cities throughout world. (2) Dams (loss of sediment supply) - sediment for longshore drift is supplied mainly by rivers that enter lake or ocean (+ eroding cliffs). Dam construction traps sediment before it reaches coastline. Many of America's rivers have been dammed, therefore > sediment is supplied from eroding cliffs, resulting in > coastal erosion. Prediction of Coastal Erosion - very complex, involves prediction of future sea levels + knowing many processes over large zone of coastline: nature + amount of sediment supply (rivers, sea cliffs); nature of wave energy (predominant direction, size); nature of coastline (straight, curved) + offshore topography; nature of sediment transport (amount of longshore drift, direction of longshore currents); nature of sediment loss (amount of sediment loss, directions of offshore currents). Without this information it is very difficult to produce successful results of mitigation (usually information is unavailable or unused, if available). Mitigation of Coastal Erosion - accelerating coastal erosion has lead to many efforts (often very costly) to prevent erosion + save property. Many efforts fail or transfer problem to another location (interfere with dynamic coastal environment, table of potential negative effects). (1) Seawalls - onshore wall of concrete or rock debris parallel to coastline (photo #1, #2, #3, #4). Purpose = protect land behind wall from wave energy, but commonly fail because wave energy comes around sides + is reflected downwards, causing erosion. Also, sediment supply is cut off. Example = Galveston, TX - City developed on barrier island. In 1900 large tropical storm washed away 2/3 of city buildings + killed 6,000. In 1902 Galveston built largest seawall ever on barrier island (16 km long, 6 m high, $15 million, photo). Seawall protected city from later storms, but beach gradually eroded. Continued development in hazardous areas. Same story for seawall (5 - 6 m high, 8 km long) along Atlantic coast-Sea Bright NJ (protect railroad + town). Residents of Daufuskie Island, SC sued state to build seawall to protect their property (seawalls banned in SC). State basically won. Video of breached seawall at Seabright, New Jersey during Hurricane Sandy in 2012. (2) Groins - wall of concrete, rock, wood, or sandbags built perpendicular to beach to trap moving sand + widen beach (sketch, photo #1, #2, #3). Groins usually successful on upcurrent side, but sediment supply for downcurrent side of beach is cut off + erosion occurs there. Downcurrent erosion can < by artificially filling beach soon after groin construction or engineering capability for allowing sediment to bypass groin (permeable groin). (3) Jetties - pair of long groins that protect harbor channel from sedimentation (photo). Because of size, jetties completely cut off longshore sediment transport, problem of upcurrent deposition + downcurrent erosion >> than for groins. Can't get around problem by artificially filling next to jetty or creating permeable jetty. Why? Example = Ocean City, MD, located on highly developed barrier island next to jetty-protected harbor. Since jetty construction in 1930's, barrier island on downcurrent side (little development) has retreated landward by ~500 m. (4) Breakwater - offshore wall parallel to coast, to absorb wave energy + provide quiet water for harbors (photo). Problem = quiet water means deposition occurs + endless cycle of dredging or sediment bypass begins (aerial photo of sand filled harbor areas. (5) Beach nourishment - bring sediment from offshore (photo, relatively cheap but commonly too fine-grained + quickly erodes away) or from other land location ($$). Examples of failed beach replenishment programs: Ocean City, NJ paid $5 million for replenished beach-storms washed it away 2 months later. Wrightsville Beach, NC = 10 beach replenishments over 25 years. In 1974 beach nourishment of Mt. Baldy area (IN Dunes National Lakeshore) brought in >250,000 yd3, + lost ~1/3 of it during first year. Important to match characteristics of sediment already on beach. Miami Beach = enormous + expensive (~$60 million) beach replenishment program, largely successful (over past 15 years or so); sand imported from Bahamas (before + after photos). Top window on this page gives an overview of shores and coastal processes as well as animated model to "Save My Beach" using groin, seawall, and breakwater.
End of Cenozoic
Quaternary past 2my climate oscillations from very cold (extensive glaciers) to warm
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See meteorite impact craters on Moon (photo #1, #2, #3, #4, #5) and on Earth (photo #1-Meteor Crater, #2-MC up close, #3, #4, #5, #6; Asteroids: Deadly Impact-National Geographic video: 6:10-7:21). (2) Role in evolution and origin (?) of life - meteorite impacts caused several mass extinctions (global dyings) during Earth history and perhaps even origin of life because some meteorites (carbonaceous chondrites) contain protein-related amino acids, building blocks of life (3) Economic Resource - certain metallic ore deposits (4) Potentially catastrophic future natural disaster - Meteorite impacts can potentially produce most catastrophic consequences of any natural disaster, potential to cause mass extinction of many organisms including human beings Terms - meteorite (link #2) = (Greek, meteoron = phenomenon of sky) piece of rock or metal (large or small) that has collided with Earth. stony meteorites resemble igneous rocks of Earth's mantle carbonaceous chondrites (photo #1, #2) = type of stony meteorite with round blebs of rock , i.e., chondrules (photo #1, #2), and abundant dark, fine-grained carbon-rich material, including organic compounds and other volatile compounds, requires formation in cold/outer regions of solar system Iron (metallic) meteorites (photo #1, #2-cut and etched, #3-cut and etched) resemble Earth's core, (stony-iron meteorites include rock and iron metal). Meteorites typically have blackened outer crust from heating due to high pressure and melting during entry into Earth's atmosphere. meteoroid = piece of rock or metal floating in space (on collision course with Earth). meteoritics = scientific study of meteorites and meteoroids. meteor (shooting star, photo #1, #2, #3) = very small (commonly ~1 mm, but ~always <1 m) pieces of rock or metal that vaporize (due to heating from intense pressure) upon entering Earth's atmosphere. meteor shower (photo) = large numbers of meteors all coming from ~same direction. asteroid (link #2, #3) = usually, but not always large (dust-size - ~1,000 km) piece of rock or metal that is usually in orbit around Sun, located in Asteroid Belt (figure), between Mars and Jupiter; ~100,000 asteroids in Asteroid Belt probably represent rocky fragments that failed to accumulate into planet (due to gravitational pull of Jupiter and relatively small volume); some asteroids are similar to Earth with iron core separated from rocky outer layer. Introduction Meteorites have played important role in human history, e.g., Islam religion has sacred rock in Mecca, Saudi Arabia, thought to be iron meteorite. On June 30, 1908, mysterious explosion occurred in Tunguska region, central Siberia. Massive fireball streaked across sky, causing incredible blast of heat and exploded ~8 km above ground; sound from explosion heard up to 1,000 km away. No deaths only because closest human was tens of km away; trees in area >1,000 km2 were destroyed and charred on one side; no crater. Explanation = 30 - 50 m comet (or stony meteorite) exploded above Earth's surface; comets (weak bodies) can easily disintegrate in Earth's atmosphere without striking Earth, producing no crater.
Greenhouse Effect
Some of incoming sunlight (visible light with short wavelength) gets absorbed by Earth, then is reradiated as longer wavelength infrared (heat) radiation, which is trapped by greenhouse gases (mainly H2O vapor and CO2, but also methane/CH4, nitrous oxide/N20, ozone/O3, and chlorofluorocarbons/CFC) in atmosphere, causing heating
Features of Beaches
Spit Barrier Islands Sea Cliffs
Volcanism
Volcanic eruptions release gases (mostly H2O, CO2, CO, and N2) as well as lava and volcanic ash. Volcanic eruptions were source of most gases in our atmosphere (except O2).
What Processes affect abundance in CO2 in atmosphere
Volcanism Chemical weathering Burning Fossil Fuels Photosynthesis Respiration
Respiration
adds CO2 - reverse of photosynthesis reaction, plants + animals use stored chemical energy to carry out life functions
Wave Period (P)
amount of time for one complete wavelength to pass given point
Glaciers' effect on landscape/floods
carves spectacular mountain peaks in some areas (e.g., Rocky Mountains and Alps); formed Great Lakes; flattens landscapes in other areas (most of Illinois), rich soil of Midwest due to deposition of glacial debris. catastrophic floods - as glaciers melted, very large lakes were created, e.g., Lake Missoula in Montana (link #2) + lake near Kankakee, IL. Dam of ice or glacial sediment (moraine) was holding water + suddenly dam gave away, resulting in huge amount of water racing across state of WA or IL. WA flood created characteristic topography called channeled scablands (link #2, #3, #4) - rough, soil-free land (washed away by flood waters), created ripples 10' high, and moved enormous boulders. IL flood carved large river valley (100' cliffs and waterfalls around Starved Rock Park area) on Illinois River.
Meteorites: Economic Resource
certain metallic ore deposits
Electromatic Spectrum
collection of all wavelengths of electromagnetic radiation from radiowaves to very short x-rays and cosmic rays
Time scale of global climate change
decades/centuries (for current/ future change) Thousands/millions (geologic examples
Flood "Control" (Construction Measures)
directed by U.S. Army Corps of Engineers. First we will introduce flood control methods involving construction measures. 1) Channelization - involves changing channel characteristics (straightening, deepening, widening, clearing debris of channel, or lining channel, e.g., with concrete). Example = Boneyard Creek in Campustown and Urbana (link #2) (see photos of scenic section of Boneyard Creek, unscenic section of Boneyard Creek, kayak run on Boneyard Creek, trip #2, guy in kayak). Allows more water to be funneled through river (faster flow). 2) Floodway (diversion channel) - transports floodwaters away from populated areas. Example = Winnipeg, Canada, constructed 47 km (29 mile) floodway around city in 1968, which << flooding from Red River (floodway loops around developed region and then dumps water back into river farther downstream) (see map + photo). 3) Dam/Reservoir - dam blocks flow of river and creates reservoir, which can be filled during heavy rainfall; Examples = Hoover Dam- Colorado River, AZ/CA; Grand Coulee Dam - Columbia River, WA; Aswan Dam - Nile River, Egypt; Three Gorges Dam (photo, map) - Yangtse River in China (largest construction project ever; see computer image of completed dam, photos from 2006 story, 2007 landslide disaster, and 2009 landslide). Detention basin (Retention pond/basin) - mini-reservoir for individual developed area or community, e.g., Boneyard Creek detention basins (photo - Phase 1, Phase 2 description plus Scott Park photo, photo - Phase 2). 4) Artificial levees - Human-made walls of sand and mud built along sides of channel to > height of riverbank (allows > flow without flooding) (photo #1, #2, #3).
Solar energy
electromatic radiation distinugished by wavelength
Barrier Island
elongate, low relief, very long (up to 100 km) islands of sand parallel to coast; barrier islands are very common along US Atlantic coast: in front of Long Island (photo), NJ, MD, VA, NC (Outer Banks, photo), + FL; also common in Gulf of Mexico. Great for recreation but bad for permanent development (dynamic environment, easy to sustain heavy damage during storms, low relief sand island). Many are densely populated.
Wave size
f wind velocity, duration of wind activity, distance over which wind blows
Spit
finger-like ridge of sediment that extends into deeper water due to longshore currents, e.g. Cape Cod MA
Early Earth Climate
first 1-2 billion years was very warm (290 degrees C)
Society Hazards of Rivers
floods that submerge land
Swells
form in one area and travel 100-1,000 km to another area
Wave Length (L)
horizontal distance from crest to crest (commonly 40-400m for ocean waves)
Coastal Hazards
hurricane/storms, tsunamis and coastal erosion.
meteor shower
large numbers of meteors all coming from ~same direction.
Climate
long term atmospheric + surface condition for area (long term average of daily weather conditions
Societal Solutions to Coastal Erosion
mapping, event warning systems, historical maps, aerial photographs, beach profiling surveys
Waves
mechanical energy moving through water. Release energy at shoreline when they break.
Meteorites: Role in evolution and origin of life
meteorite impacts caused several mass extinctions (global dyings) during Earth history and perhaps even origin of life because some meteorites (carbonaceous chondrites) contain protein-related amino acids, building blocks of life
coldhouse
much colder climate. Iceage
hothouse
much warmer climate
Mitigation- Meteorite Impacts
only natural disaster that we can potentially PREVENT by deflecting or destroying (e.g., with nuclear bomb explosion on object), but we would need much advance warning (~10 years). First step = detect and track most dangerous objects; done for ~half of large (>1 km) NEOs and none of small (<1 km) NEOs (too many and too difficult to find). Missions to land on asteroids and comets are important step in mitigation
meteoroid
piece of rock or metal floating in space (on collision course with Earth).
Chemical Weathering
removes Co2 Chemical weathering reaction of silicate or carbonate mineral is CO2 + H2O + silicate/carbonate mineral ---> dissolved ions + HCO3- Weathering removes CO2 gas from atmosphere and adds it to oceans (as HCO3-). Increasing chemical weathering of rock causes < CO2 in atmosphere.
Iron (metallic) meteorites
resemble Earth's core, (stony-iron meteorites include rock and iron metal). Meteorites typically have blackened outer crust from heating due to high pressure and melting during entry into Earth's atmosphere.
stony meteorites
resemble igneous rocks of Earth's mantle
meteoritics
scientific study of meteorites and meteoroids.
Crest
top of the wave
carbonaceous chondrites
type of stony meteorite with round blebs of rock , i.e., chondrules (photo #1, #2), and abundant dark, fine-grained carbon-rich material, including organic compounds and other volatile compounds, requires formation in cold/outer regions of solar system
Predicting future climate
understand geologic past to help predict future (inverse uniformitarianism)
Society benefits of Rivers
used as a source of water, for obtaining food, for transport, as a defensive measure, as a source of hydropower to drive machinery, for bathing, and as a means of disposing of waste.
Photosynthesis
using light energy, plants convert CO2 gas into food (chemical) energy. Simplified version of photosynthesis reaction is: CO2 gas + sunlight ---> C (organic matter in form of sugar) + O2 Above reaction is reverse of fossil fuel combustion reaction. Increasing amount of plant life means < CO2 in atmosphere.
asteroid
usually, but not always large (dust-size - ~1,000 km) piece of rock or metal that is usually in orbit around Sun, located in Asteroid Belt (figure), between Mars and Jupiter; ~100,000 asteroids in Asteroid Belt probably represent rocky fragments that failed to accumulate into planet (due to gravitational pull of Jupiter and relatively small volume); some asteroids are similar to Earth with iron core separated from rocky outer layer.
Wave Height (H)
vertical distance from crest to trough (2-5 m in normal ocean, up to 15m in storm)
meteor (shooting star)
very small (commonly ~1 mm, but ~always <1 m) pieces of rock or metal that vaporize (due to heating from intense pressure) upon entering Earth's atmosphere.
Sea Cliffs
wave erosion can undermine cliff, causing landslides. Avoid building near sea cliffs (potential for erosion + property loss).
Coastlines
where land meets ocean or large lake. Included beaches (surf zones) estuaries (semi enclosed bodies of mixed fresh and salt water that attract many organisms
Chicago Area Lakeshore
~100 km along southwest coastline of Lake Michigan: borders most densely populated area in Great Lakes region + includes some of most highly engineered + human-altered settings in region.
Chicago Area Lakeshore
~100 km along southwest coastline of Lake Michigan; borders most densely populated area in Great Lakes region + includes some of most highly engineered + human-altered settings in region. Three types of coastal areas (see geologic map + topographic map):
End of Mesozoic
~100-50 mya was very warm
End of Paleozoic Climate
~300 mya was very cold extensive glaciers
Cenozoic cooling
(50 - 2 m.y.a.) - after hothouse climate, Earth cooled progressively. Several factors probably involved but major one was related to plate tectonics. Beginning ~45 m.y.a., India began to collide with Eurasia (continent-continent collision zone), resulting in enormous mountain range (Himalayas, uplift of Tibetan plateau). Creation of enormous mountain range exposed enormous amount of silicate + carbonate rock to chemical weathering. Steep slopes would erode quickly exposing new fresh rock. Chemical weathering of silicate + carbonate rock < levels of CO2 gas, which in turn caused global cooling. There is also evidence for >> marine plants (diatoms), causing > photosynthesis + < CO2 gas. Explosion in abundance of diatoms may be due to change in ocean circulation patterns (> upwelling of cold, nutrient-rich water). (Other factors = distribution of land + ocean masses, > reflectivity of Earth + change in ocean + atmospheric circulation patterns.
Meteorite
(Greek, meteoron = phenomenon of sky) piece of rock or metal (large or small) that has collided with Earth.
Large change in climate...
(major warming or cooling) = impact on agricultural productivity/ecosystems and even population migration - If significant global warming occurs, some areas will become much drier (others wetter), causing deserts (> irrigation or << agricultural productivity), other possible effects include > severe weather and > disease (sleeping sickness, malaria, yellow fever); if glaciers (or deserts) advance over large areas, people will have to move and agricultural productivity will <<.
Scars from those ancient collisions (craters = bowl-shaped depressions produced from meteorite collision) are still clearly visible on Moon, but far fewer impact craters on Earth. Why?
-Very small meteorites vaporize upon entering Earth's atmosphere; moon has no atmosphere its impacted by meteorites 1 foot or smaller - On Earth, weathering and erosion erase impact craters over time moon has no liquid water or gaseous CO2, therefore no weathering and erosion
Meteorites: Potentially catastrophic future natural disaster
-potentially produce most catastrophic consequences of any natural disaster, -potential to cause mass extinction
Coastal Erosion Control Measures Along Southwestern Lake Michigan
1) Revetments (~seawall/lakewall) - Chicago coastline - rock-filled cribs designed to absorb wave energy; many built in late 1800's + early 1900's - deteriorating + need repair, about half have been repaired that need it. Bluffs area - although much of bluffs area is protected by revetments (lakewalls) (+ some groins, all built privately), wave energy is reflected downward + beginning to undermine protective barriers; potential for massive erosion if those structures are lost. Army Corps of Engineers proposes to line lake bottom near that coast with cobbles to "strengthen" area. 2) Groins - examples in Chicago (North Avenue-Fullerton Beach, photo + Hollywood/Ardmore) What is dominant longshore current direction? Why? 3) Jetties - Waukegan harbor (just south of IL Beach State Park); used to be jetty along Chicago River 4) Breakwaters - Lake Forest, photo (~30 km north of Chicago in steep slopes) 5) Beach nourishment - IL Beach State Park is experiencing major beach erosion because sand supply is cut off from north (beach protection measures in WI), shoreline receding as much as 3 m per year. In north part of park there used to be housing development (in 1960's + 70's), but massive erosion + failed coastal erosion control measures led to demolition + abandonment of entire development. IL purchased properties along + in from coastline + created north unit of park. IL Dept. of Natural Resources combat on-going erosion by providing beach nourishment of ~40,000 yard3/year at a cost of $1 million. For stable beach, area needs ~80,000 yard3/year
Burning Fossil Fuels
Adds CO2. burning of any carbon-based fuel (coal, oil, natural gas, wood, leaves, + ethanol) involves production of CO2 gas: C (organic matter) + O2 ---> CO2 gas + heat
Cape Hatteras Lighthouse Controversy (North Carolina)
Cape Hatteras Lighthouse (photo #1 , #2) is located on North Carolina's Outer Banks, 200 km line of barrier islands (aerial photo). Banks are known for "capes" (seaward projections of land), e.g., Cape Hatteras, Cape Fear, + Cape Lookout. Cape Hatteras, easternmost point of NC, long known as "graveyard of Atlantic" due to many ship groundings on nearby shoals during storms. Cape Hatteras lighthouse is tallest brick lighthouse in world (~60+ m), listed on National Register of Historic Places (detailed proposal for Cape Hatteras Lighthouse as National Historic Landmark) + located on Cape Hatteras National Seashore. Built in 1870 with state of art lenses, it has saved ocean-going boats + hosted millions of tourists. Original location was ~460 m (1,500 ft) from coastline but rising sealevel + flat slopes greatly reduced that distance (1980 - waves lapping at base). Many costly erosion control measures were attempted by National Park Service + US Army Corps of Engineers including groins, beach nourishment, breakwater, + seawall. All were unsuccessful. Consider merits of 3 options: a) Build very large seawall ($5.6 million). b) Do nothing + eventually lose lighthouse. c) Move ~5,000 ton lighthouse to new area ~500 m inland (~$12 million, link #2, photos of move, long road ahead, on tracks, tracks at ground level, under the lighthouse, pushjacks - #4, almost there - #5, old and new positions - #6). Which option should be done + why? There is a similar controversy involving the Montauk lighthouse on Long Island, NY (story, photo). The US Army Corps of Engineers has decided to build a $14 million seawall in an attempt to save this historic lighthouse (article), which was commissioned by Pres. George Washington + completed in 1796. Seawall opposed by surfing group.
Future Risk - Meteorite Impacts
Collision of 10-km meteorite with Earth would be ULTIMATE global catastrophe/disaster and result in mass extinction, Hoever collision of 10-km meteorite probably occurs only every 100 m.y. (determined by frequency of impact craters on Moon, where weathering and subduction don't erase them over time). 1-km meteorite can devastate most nations and 50 - 100 m objects could level whole cities In March 1989, 500 m meteorite crossed Earth's orbit and missed us by 6 hours (<700,000 km)! There are 1,000 large (>1 km) near Earth objects (NEOs = asteroids or comets that come relatively close to Earth) and ~1,000,000 small (>50 m) NEOs. Over 50 years, risk of dying from meteorite collision estimated at 1 in 40,000. Although event itself (>1 km meteorite impact) has low probability (every 100,000 years), there will be huge number of deaths (~1.5 billion).
Effects of urbanization
Development of cities around rivers can intensify effects of flooding (> flood size, > flood frequency, < lag time, sketch of hydrograph). Why are effects of flooding intensified? A) Creation of impermeable barriers (photo #1, #2) - concrete, pavement, and buildings prevent infiltration and enhance runoff B) Street Sewers (photo) - underground tunnels that send water from streets directly into nearest river. C) Buildings in floodplain take up space D) Construction (clearing vegetation cover, photo) - easily eroded sediment can fill river channel Urbanization effects are greatest for smaller rainstorm events. For big storms, urbanization effect is limited (system is overwhelmed and sewers and pavement don't make much difference)
Importance of studying climate
Effect on sea level Large change in climate Glaciers' effect on landscapes/floods Predict future climate
Floods
Flood (link #2, #3, #4, photo-Cedar Rapids, Iowa-6/08) - river overflows its channel due to excessive discharge. For average river in humid climate, flooding occurs every ~1 - 2 years. Problem = Floods are most widespread geologic hazard, affecting more people than all other geologic hazards. In USA, ~20,000 communities, 6 million homes (~10% of US population) are located on flood-prone land, resulting in ~$6 billion damage and ~140 deaths per year. See USA map of Presidential disaster declarations involving floods from 1965 - 2003, where green = 1 declaration, yellow = 2 declarations, orange = 3 declarations, and red = 4 or more declarations. Annual flood damage in USA has > by 30x over 70 years, after adjusting for inflation. Why?
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Flood Hazard Map - uses stage vs. recurrence data + topographic map to plot 50 year floodplain or 100 year floodplain on map (all area surrounding river valley up to certain elevation); critical information for land use planning. II) Effects of Urbanization Development of cities around rivers can intensify effects of flooding (> flood size, > flood frequency, < lag time, sketch of hydrograph). Why are effects of flooding intensified? A) Creation of impermeable barriers (photo #1, #2) - concrete, pavement, and buildings prevent infiltration and enhance runoff B) Street Sewers (photo) - underground tunnels that send water from streets directly into nearest river. C) Buildings in floodplain take up space D) Construction (clearing vegetation cover, photo) - easily eroded sediment can fill river channel Urbanization effects are greatest for smaller rainstorm events. For big storms, urbanization effect is limited (system is overwhelmed and sewers and pavement don't make much difference). III) Flood Mitigation (Public Policy) 1) Preserve wetlands (swamps, photo) - excellent locations for rainwater infiltration into ground, rather than running off into river; ~50% of world's wetlands have been lost over past 200 years. 2) Public education - about risks of floods, floodplain, flood frequency, etc. 3) Mapping and zoning - determine areas of risk and restrict land use (allow only parks, golf courses, agriculture); most effective approach from environmental perspective. Zoning restrictions only apply to new construction. 4) Mandatory insurance - Require those who live on floodplain to have insurance (for homes and crops). Offered by Federal Emergency Management Agency (FEMA, logo) since 1950s but not very popular; National Flood Insurance Program is $24 billion in debt, mostly caused by payouts after Hurricane Katrina and Hurricane Sandy (graph); most policy-holders have taxpayer-subsidized rates, recent legislation aims to reduce that problem. 5) Relocate - Give government aid for high-risk communities to move, e.g., Valmeyer, IL (photo during 1993 flood).
Without the Greenhouse Effect
Heat absorption raises average temperature of Earth, and makes Earth habitable planet. Without greenhouse effect (i.e., no atmosphere), average temperature on Earth would be ~33°C colder and water would be frozen. In addition, we would see enormous swings in daily temperatures, similar to those of Moon. On sunlit side, Earth's temperature would be close to boiling (all solar energy is transmitted to Earth and absorbed, causing heating), but dark side would be far below freezing (all energy lost to space).
Causes of Floods
Heavy Rain Rapid Snow Melt Coastal storm surge Dam failure
Coastal hazards: humans
Human intervention occurs to protect developed areas from coastal erosion which fail or transfer problem elsewhere.
Dinosaur Extinction
Impact by large meteorite/asteroid - Proposed in 1979 by Nobel physics laureate Luis Alvarez and his son (geologist) Walter Alvarez. Idea explains dinosaur extinction by collision with Earth of very large meteorite or comet (~10 km) that occurred ~65 m.y. ago. Because of large size (millions of megatons) and high speed (80,000 km/hr), force released upon impact is equivalent to detonation of ~1,000x entire nuclear arsenal of world at single point How do we know? 1) Evidence from clay layer deposited at end of Mesozoic Era - Distinctive thin clay layer at end of Mesozoic/beginning of Cenozoic (photo) (K/T boundary). Layer is rich in elements (iridium) normally abundant only in meteorites, and it contains metamorphosed quartz grains (with lineations called shock lamellae) only found in known meteorite impact sites (or nuclear explosions), tektites (glassy blebs produced by melting of rock during impact) and pieces of carbon (from fires). 2) Large, buried impact crater in southeast Mexico - ~200 km (right size), formed at 65 m.y. (right time) B) Volcanic Eruptions - Many Hawaiian-type volcanoes erupted at ~65 m.y. They would also eject dust into atmosphere and block sunlight. Possibly meteorite impact triggered volcanic eruptions, which further blocked sunlight. Or they may have just happened to coincide in time. Actual answer may be combination of both mechanisms as well as other gradual environmental changes, e.g., changing climates. Recent evidence that largest mass extinction event ever (end of Paleozoic) may have involved large meteorite collision.
Meteorites have played important role in human history...
Islam religion has sacred rock in Mecca, Saudi Arabia, thought to be iron meteorite.
Lake Levels + Coastline Changes
Lake levels are more variable than sea level + depend on regional precipitation (heavy rains = high lake levels) + human controls (e.g., dams).) From 1860 to 2011 total variation in level of Lake Michigan is ~2 m; historic high in 1986 + historic low in 1964. In natural state (before mid-1800's), much of IL shoreline was highly vulnerable to wave erosion. Now most of shore is "protected", but erosion remains problem, especially during high lake water levels. ~Small changes in lake level can cause large changes in beach width + coastline position for areas with shallow slope (Chicago + IL Beach State Park). In Chicago, biggest change in shoreline was from lake filling, which began in mid 1800's but most occurred from 1920 - 1940. Added 5.5 mile2 of coastline by dumping 57 million yd3 of sand (from offshore IN), construction debris, + urban waste (+ debris from 1871 fire).
Three Types of Coastal Areas
Lake plain Glacial till cliffs Beach ridges
Chicago Area Lakeshore: Three types of coastal areas (see geologic map + topographic map):
Lake plain (flat) : extends for ~50 km from IN border to Wilmette (all of Chicago), most of area is used for city parks. Located on silt + mud that formed from glacial Lake Chicago (precursor to Lake Michigan, larger lake stage when glaciers of last Ice Age were melting) (2) Glacial till cliffs (steep) - extends for ~35 km from Wilmette to Waukegan, IL; ~all is developed with expensive homes. Located on hills (moraines, up to ~30 m above lake level) of unsorted sediment (till - wide range in grain sizes from finest mud to large boulders, photo) deposited directly by glacial ice. (3) Beach ridges (flat) - extends for ~15 km from WI border to Waukegan, IL, mostly within IL Beach State Park (link #2), small dunes formed over past several thousand years due to build up of longshore drift.
Recent Meteorite Impact- Arizona USA
On Dec. 10, 2013 a meteor flashed across the Arizona sky and caused a large explosion, which did not produce damage on the ground. It was associated with the Gemini meteor shower, which is an unusual meteor shower caused by a rocky asteroid rather than a comet.
Recent Meteorite Impacts- Chelyabinsk, Russia
On Feb. 15, 2013 over the Ural region of Russia, a meteor streaked across the sky at a speed of about 67,000 km/hr (18.6 km/sec, or about 50 times the speed of sound) and shattered over the city of Chelyabinsk (a city of 1 million about 1,500 kilometers east of Moscow) and then hit Lake Chebarkul (story in Nature; photos, video, NOVA video). The meteor was an estimated 17 - 20 m (56 - 66 ft) wide, weighed an estimated 11,000 tons, was of stony (rather than iron metallic) composition, and probably came from the Asteroid Belt. The mid-air blast, which occurred at an altitude of 30 - 50 km, released an energy equivalent to nearly 500 kilotons of TNT, which would make it 20-30 times more powerful than the atomic bombs detonated at Hiroshima and Nagasaki. The meteor was moving along a low trajectory. Around 1,500 people were reported injured, mainly due to glass from shattered windows. Two people were reported in serious condition with a 52-year-old woman with a broken spine flown to Moscow for treatment. Over 7,200 buildings in six cities across the region were damaged due to the explosion and impacts. An estimated 200,000 square kilometers (77,220 square miles) of glass were broken. Damage is estimated at $33 million. The vaporization of the meteor in the sky created a dazzling light, bright enough to cast shadows in Chelyabinsk and to be observed in the Sverdlovsk oblast, Orenburg and Kazakhstan. The meteor was the largest reported since 1908, when the famous Tunguska event took place in remote Siberia, and the only known such event to result in a large number of injuries. An event of this magnitude is expected to occur once in 100 years on average.
Meteorite Case History: Siberia
On June 30, 1908, mysterious explosion occurred in Tunguska region, central Siberia. Massive fireball streaked across sky, causing incredible blast of heat and exploded ~8 km above ground; sound from explosion heard up to 1,000 km away. No deaths only because closest human was tens of km away; trees in area >1,000 km2 were destroyed and charred on one side; no crater. Explanation = 30 - 50 m comet (or stony meteorite) exploded above Earth's surface; comets (weak bodies) can easily disintegrate in Earth's atmosphere without striking Earth, producing no crater
Recent Meteorite Impacts-Canada
On Nov. 20, 2008 a ~10 ton stony meteorite lit up the skies and struck western Canada near the border of Alberta and Saskatchewan (link #1, #2, location map). It exploded with the force of ~100 tons of dynamite before reaching the ground and may have broken into as many as 1,000 pieces or more. Its spectacular and fiery descent was seen up to 700 km away by many people and captured on video (video #1, video #2). Scientists are trying to find as many pieces of the meteorite as possible before snow and the Canadian winter takes over. They found over 1,000 meteorite pieces (a world record), with the largest piece weighing 29 pounds.
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Origin of Meteorites (1) Asteroid belt - Gravitational attraction of nearby Jupiter disrupts asteroids from regular orbit, causing them to crash into each other. Collisions can send ~large asteroids or smaller pieces into orbits toward inner planets (Apollo objects/Earth-crossing asteroids). 150 Apollo objects are > 1 km and could cause massive destruction during impact. (Small number of meteorites consist of rock from our Moon or Mars; produced when asteroid collides with Moon or Mars, breaking off pieces of that body and sending them to Earth.) (2) Comets (photo, up close of comet 67P/Churyumov-Gerasimenko) - bright objects consisting of dust and frozen gases (mostly loose snow, i.e., frozen H2O but also NH3, CH4, CO2, and CO), similar in composition to outer planets, with long tail that always points away from Sun; comets originate beyond margins of our solar system and approach Sun in wide elliptical orbits. Sublimating ice (solid to vapor) and dust are carried away by solar wind (stream of nuclear particles from Sun) as comet approaches Sun, forming characteristic tail. Example = Halley's Comet, 76 year orbit cycle and last seen from Earth in 1986. Most regularly occurring meteor showers (e.g., Perseid and Leonid) consist of swarms of small, glowing pieces of comet (break apart easily) entering Earth's atmosphere. Five-year Near Earth Asteroid Rendezvous mission (NEAR) placed spacecraft in close orbit with asteroid known as 433 Eros to learn more about geology and physical properties of NEOs. Eros is large rocky, peanut-shaped asteroid, ~33 km long by 13 km around with cratered surface, some up to 6 km (4 miles) across. NEAR mission ended dramatically with spacecraft landing on surface of Eros in February 2001. Ten-year Rosetta mission by European Space Agency landed a probe onto 67P/Churyumov-Gerasimenko comet (photo, ~4 km at longest and widest dimension) around 300 million miles away on Nov. 12, 2014, becoming the first spacecraft to land on a comet nucleus. Unfortunately it bounced on the comet's surface twice and came down next to a cliff in a tilted orientation (photo) shielded from the sun, which reduced the lifespan of its solar-powered batteries. It did, however, detect organic molecules, which are necessary for life. Rosetta's mission will continue until December 2015, following comet 67P as it swings back away from the sun (figures). Meteorite Impact Events - Each day ~100 tons of meteorites strike Earth's atmosphere but most are small enough (<1 m) to be vaporized by heating due to high pressure as they fall through atmosphere (very small, <1µm, pieces are slowed greatly and fall like snow). Larger objects (>1 m and >350 tons) are not slowed and hit Earth with very high speed (80,000 km/hr), releasing huge force and produce impact crater. Jet stream of rock and dust (ejecta), is sent in all directions from impact point, producing blanket of ejecta, which thins away from crater. Such events are simulated in laboratory experiments (Asteroids: Deadly Impact-National Geographic video: 16:30-18:13). Force from collision compresses and fractures underlying rock and sends shock waves and heat into ground. Due to intense pressure, minerals can convert to denser forms, e.g., quartz to stishovite and coesite. Intense heat from impact can cause melting of rock on crater floor. Meteorite is usually pulverized by collision but small pieces may be preserved. Rock along crater walls slides into hole, enlarging crater size to ~10 - 20 x meteorite size. For collision of large (>100 - 200 m) meteorite, get uplifted area in middle of crater (photo #1 vs. #2 with no uplift) due to complex interactions of shock waves, gravity, and strength of rocks. Shock waves rebound upward sending molten rock into air, where it cools quickly to form impact-derived glass particles (tektites, photo). ~150 known impact craters on Earth, most are < 200 m.y. in age and > 5 km wide. Why mostly relatively young and large ones? World famous impact crater ~100 miles NE of C-U (Kentland, IN). Buried impact craters at Des Plaines, IL (near Chicago O'Hare airport) and Glasford, IL (near Peoria) Other effects of very large (>10 km) meteorite = tsunamis (if impact in ocean); massive earthquakes; melting of large part of crust (and some mantle) and asteroid; molten rock sent skyward and falls like rain, igniting global fires, and sending soot into upper atmosphere, dust (ejecta) and soot in atmosphere form thick, dark cloud to block sunlight around globe for months, causing global cooling ("nuclear winter scenario") and death of plants (no photosynthesis) and animals up food chain; eventually atmospheric dust (and tektites and soot) settles on ground providing global "signature" of impact; longer term effects = acid rain (due to heating, N2 and O2 in atmosphere combine to produce nitric acid) and if impact occurred in ocean, get global warming due to enhanced greenhouse effect (> H2O vapor). Geologic Record of Mass Extinction Extinction - disappearance of plants or animals on global scale, fossil evidence indicates that extinction has occurred ~continuously over geologic time, but during certain time periods there were very high rates of extinction, e.g., several times during Paleozoic, end of Paleozoic (90 - 95% of all species of marine organisms and many terrestrial organisms), end of Mesozoic (50% of all life on Earth), today (past 50 - 100 yrs). These events are called mass extinctions. Examples of causes of mass extinction Disruption of food chain or disease Change in climate - can be caused in many ways such as: Movement of continents (gradual effect) Tectonic Mountain building (gradual effect) Tectonic Meteorite collision with Earth (sudden effect) Extraterrestrial All of above can be interrelated. Focus on mass extinction event at end of Mesozoic Era, involving dinosaurs. Dinosaur ("terrible lizard") Group of extinct reptiles that lived during Mesozoic Era, had upright posture, most were land-dwellers, included herbivores (which walked on all 4 feet or back legs only) and carnivores (most of which walked on back legs). Dinosaurs include largest land animals ever and are considered to be most successful land animal. Lived for 160 m.y. (from 225 m.y. to ~65 m.y.). Flourished for long time and then went extinct abruptly. Why? To be answered next class.
Importance of Understanding Meteorite impacts
Origin of the Earth/Solar system, tole in evolution and origin of life, economic resource, potentially catastrophic
Earth vs. the Sun
Sun (surface temperature = 6,000°C) emits much of its energy as visible light. Earth is much cooler and emits much less radiation (lower intensity), ~ entirely as longer wavelength infrared radiation (figure).