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186 Cards in this Set
- Front
- Back
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Wildfire |
Uncontrolled fire in a natural setting |
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How are fires changing (in terms of size)? |
- Wildfires increasing in frequency and size - 11.5 KA increase - Changes possibly due to human activities or climate warming |
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How much do wildfires cost us annually? |
- >$3 billion per year fighting fires - 44 million homes in areas at high risk for wildfires - 20 firefighter fatalities annually (increasing in #s) |
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What kind of chemical reactions occur when we have a fire? |
- Rapid, high temperature reaction (combustion) releases heat, lights, and other products - Combustion results in fast break down of organic material |
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What products are produced from chemical reactions of fire? |
- CO2 and H2O - Traces gases (e.g. carbon monoxide, hydrocarbons like methane) - Ash and soot (powdery residues that accumulate after burning) contribute to smoke |
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Ash |
Mineral compounds |
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Soot |
Unburned carbon |
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3 phases of fire - Preignition |
- Absorbs energy, then we get ignition and combustion - Fuel is brought to a temp and water content favoring ignition through preheating and pyrolysis |
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Preheating |
- Part of preignition - Fuel loses water and other volatile chemical compounds |
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Pyrolysis |
- Part of preignition - Process that chemically degrade fuel (large molecules break down); heats up chemicals to break them down which makes them burn easier |
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3 phases of fire - Combustion |
- Exothermic reactions release energy as heat and light - 2 types: flaming and smouldering |
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Flaming combustion |
- Rapid oxidation process - Flames - Pyrolysis of woody materials |
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Smoldering combustion |
- Carbon and ash blanket new fuel, inhibiting flames - Produces charcoal - Glows |
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3 phases of fire - Extinction |
- Combustion, including smoldering, ceases - Insufficient heat and fuel to sustain combustion - Occurs when part of "fire triangle" is taken away |
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3 phases of fire |
1) Preignition 2) Combustion 3) Extinction |
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"Fire triangle" ingredients |
- Combustible substance (fuel)
- Temperature high enough to cause combustion (heat) - Enough oxygen to sustain combustion (>16%) |
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3 mechanisms by which fires transfer energy |
1. Conduction 2. Convection 3. Radiation |
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Conduction |
heat passes through material (e.g. logs, branches) and drives off moisture |
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Convection |
heated air and gases rise (density driven), pulls in air at lower levels |
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Radiation |
radiated heat through space |
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Pros of wildfires |
- Some plants need fire to release seeds - Increases soil nutrient content - Successional communities (add variability) - Kills ticks |
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Cons of wildfires |
- Property destruction - Increased landslide risk due to devegetationIncreased flood risk (hydrophobic soil layers) - Release of soot/ash/aerosols into atmosphere - Pyrocumulonimbus clouds can form |
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What was the United States’ fire policy for most of the last century, and how has this impacted current fires? |
- We advocated for fire suppression, which allowed “fuel” to build up, so when a fire does start it would be much harder/impossible to put out - Smokey the bear telling the wrong idea |
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3 factors that determine wildfire behavior? |
1. Fuel 2. Topography 3. Weather |
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3 factors that determine wildfire behavior - Fuel |
- Fuel suppression (allowed "fuel" to build up, so when a fire does start it would be much harder to put out) - Fires can be regulatory for reducing buildup of fuels |
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3 factors that determine wildfire behavior - Topography |
- In U.S., south-facing slopes are warm and dry, lower moisture content favors combustion - In mountainous areas, wind moves upslope - Fires on steep slopes preheat fuel upslope, increasing rate of fire movement (fires move up slopes very quickly) |
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3 factors that determine wildfire behavior - Weather |
- Dominant influence on wildfires - Large fires are more common following drought (droughts reduce fuel moisture content) - Winds influence spread, intensity, and form of wildfire - Get worst wildfires in areas that experience both wet and dry conditions |
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How do winds influence wildfires? |
- Fire tilts, so you get more preheating - Wind is pushing the fire to fuel - Can lead to front fires up to a mile in front of main fire |
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What job do hotshot firefighters perform? |
- Build fire breaks - Aim to get to bare ground that the fire can’t jump - Back burning - set small fires that races toward the main fire to get rid of the main fire’s fuel so that it puts itself out |
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3 types of fires |
- Ground fires - Surface fires - Crown fires - Fires are classified according to layer of fuel allowing the fire to spread |
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3 types of fires - Ground fires |
- Subsurface - Burn organics in soil (mostly smoldering combustion) |
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3 types of fires - Surface fires |
- Above ground
- Burn grass and shrubs - Can move rapidly |
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3 types of fires - Crown fires |
- MOST difficult to put out - Burning in crowns of trees, chaparral - Flaming combustion carried through tree canopies - Usually generated by strong winds and aided by steep slopes - Will grow as long as conditions favorable: nearly impossible |
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Stream |
- Any flowing body of water, large or small - Move water (either in laminar or turbulent flow) - Weather the material (bedrock or sediment) that they flow over - Transport sediment (erosion) |
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River |
- Major branches of a large stream system - Cary 16 billion tons of sediment and 2-4 billion tons of dissolved material per year |
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How do streams form? |
- At first, water flows across the ground surface as overland or sheet flow by stream’s headwaters - Eventually, it erodes depressions, and flows in a channel - Channels form a network of tributaries: collect water and feed it into the main trunk stream |
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Drainage basin |
Extent or an area of land where all surface water from rain, melting snow, or ice converges to a single point at a lower elevation, usually exit the basin, where the waters join another body of water, such as a river, lake, reservoir, estuary, wetland, sea, or ocean |
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Drainage divide |
Boundary b/w basins |
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What does it mean for drainage networks to have a “dendritic” shape? |
It looks like a tree |
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Laminar flow |
- Water moves in parallel lines - Individual paths maintain their velocities - Like when you gently turn a faucet on |
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Turbulent flow |
- Water does not move in parallel lines - Changes in velocity in individual streams - Like when you turn a sink on really hard - Loosens and lifts material from stream bed using water pressure - MOST COMMON |
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How do rivers weather materials? |
1. Abrasion 2. Turbulent flow 3. Dissolution |
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Weathering - Abrasion |
Water-borne particles physically break off pieces of other particles they come into contact with |
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Weathering - Turbulent flow |
Loosens and lifts material from stream bed using water pressure |
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Weathering - Dissolution |
Chemical weather of soluble material (will dissolve in water) |
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How do rivers erode/transport materials? |
1. Bed load 2. Suspended load 3. Dissolved load |
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Transportation - Bed load |
Sediment is bounced and rolled across the stream bed (large clasts) |
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Transportation - Suspended load |
- Sediment is suspended by the water (medium/small clasts) - Sediments no longer in contact w/ bottom |
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Transportation - Dissolved load |
Stuff that is dissolved in the water (sodium, calcium, etc.) and moves down the river |
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Would you expect larger particles to be transported in the bed load or in the suspended load? Why? |
Larger particles would be transported in the bed load because the bed load consists of other sediments that are bounced and rolled down the stream bed, and larger particles are going to be heavier so this would be their way of transport |
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For a particular stream, is the bed load always composed of particles of the exact same size, or can it change through time? If it can change, what kind of event would allow the stream to carry bigger (or force it to only carry smaller) particles? |
- Particles will never be the same size, but will all be big enough to have to stay rolling on the ground - If stream has more water in it, more particles can move out of bed load - Velocity can move particles out of bed load - Big flood would increase velocity |
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Gradient |
Gradient = (elevation change) / (distance measured along channel) - Gradient shows how fast the stream is dropping/sloping |
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What does it mean for a stream to have a higher gradient? |
- Steeper stream - Stream is not as meandering, because length is different |
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Base level |
Level to which a stream can erode |
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Ultimate base level |
Sea level |
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Dams |
- Increase erosion and weathering downstream b/c they stop sediment transport by forming new local base level - Since all sediment gets stuck above the dam, the lower reaches of the stream get "starved" |
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Meandering stream |
- Low sediment load - Low velocity - One main channel - Common in streams flowing on low slopes in plains or lowlands, cutting through fine sand/silt/mud - Flow on flat floodplains, create meanders |
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What type of stream is the Iowa River an example of? |
Meandering stream |
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Braided stream |
- High sediment load - High velocity - Many channels - May have large variations in flow volume, easily eroded banks/terrain (mouth of canyon, end of glacier, etc.) - Fast-moving sediment-laden water cuts across sediments at edges of existing channels, creating shallow, braided channels - Have very unstable stream walls, so stream moves all over the place and vegetation has a hard time forming |
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Know where erosion and deposition occur on a diagram of a meandering stream. |
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Cut bank |
- Outside bank of water channel (stream), which is continually undergoing erosion - Erosion |
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Point bar |
- Alluvial deposit that forms by accretion on the inner side of an expanding loop of a river - Deposition |
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Meander scar |
- Geological feature formed by the remnants of a meandering water channel - Often formed during the creation of oxbow lakes |
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Oxbow lake |
Abandoned loop of a meandering river |
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Flood plain |
- Flat, low-lying area along channel subject to floods - Fine grained sediment - Adjacent to channel and subject to floods |
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Levee |
- Result from deposition accumulation of sediment along banks during flood event |
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Discharge |
- Represents how much water is actually passing a point at any given time - Cfs-cubic feet/second |
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Stage |
- Measures stream height - Once water height is high enough to jeopardize human structures/safety, flood stage is reached |
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Different types of floods |
1. Flash floods 2. Ice-jam floods 3. Dam failure floods 4. Regional floods |
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Flash floods |
Intense local rainfall causes stream to suddenly flood small area (usually local watershed) |
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Ice-jam floods |
Melting ice-floes dam a portion of a river (normally in spring) causing it to flood upstream |
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Dam failure floods |
More often than not result of faulty engineering (NOT natural disasters) |
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Regional floods |
- River overflows banks on a large scale, flooding entire regions - Happen often in the W b/c of the Mississippi River |
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Johnstown, PA dam failure |
- Worst flash flood in US history - 2,209 dead - May 31, 1889 - Telegraph lines washed away - Conemaugh River floods Johnstown, traps people in homes - The dam (1650 ft elevation) was made of mud and clay and was breached by heavy rain, so 20 million tons of lake drained downstream at 40 mph and up to 60 ft high - Wave filled with debris - 1 of every 3 victims never identified (777) |
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What factors contributed to make the 1993 Mississippi River floods so devastating? |
- Entire upper Mississippi river basin - Regional Flood - Wet fall 1992 and heavy snowfall in winter saturated soils in U. Mississippi - Entire region had above average rain beginning in April - Over 50 fatalities and $15 billion in damages - 50,000 homes destroyed or damaged - 75 towns submerged - 100 year flood for Iowa City |
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What type of flooding event causes the most fatalities, and what causes 50% of the fatalities WITHIN these sorts of events? |
- Flash flooding causes the most fatalities - 50% of flash flood fatalities are vehicle related (trapped and drown) |
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How much water does it take to stall a passenger car? How much to carry away most vehicles? |
- 6 inches will stall most passenger cars (and can knock you over) - 12” will float many vehicles - 24” will carry away most vehicles |
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What is a recurrence interval, and how do we calculate it? |
- Statistical average of # of years b/w flows of a certain peak discharge or streamflow - R = (N+1)/m --- R is recurrence interval --- N is # of floods w/i the time span --- m is the rank of flood |
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Know the probability of a flood of a given recurrence interval occurring any specific year |
- 50 year flood = 2% - 100 year flood = 1% - 500 year flood = 0.2% |
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Can we have two 500-year floods in a 3-week period? |
Yes - recurrence intervals are statistics of past occurrences and do not predict the future |
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What happens when we have a new largest flood to the recurrence interval of the now second largest flood? |
Each new largest flood makes recurrence interval of now 2nd largest flood drop by ~1/2 |
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Does the Coralville Dam and Reservoir stop large floods from occurring? |
- CAN’T stop large floods - Can stop small floods by regulating flow |
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What is wrong with our current definitions of flood plains in Iowa City? |
- They don’t listen to the geologists and weren’t drawn correctly to begin with - Build in flood hazard zones - Floodplains have not be redrawn |
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Hydrograph |
- Plots of stream flow vs. time - Used to show how the water flow in a drainage basin (particularly river runoff) responds to a period of rain - When gradients are steep, water runs off faster/reaches the river more quickly - Areas of permeable rocks and soil allow more infiltration and so less surface runoff |
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How does modifying land use (making it more urban) change the shape of a hydrograph, and why? |
- Modifies how a river responds to precipitation - Vegetation intercepts precipitation and allows evaporation to take place directly into the atmosphere so reducing the amount of water available for overland flow while the large # of impermeable surfaces in urban areas encourages runoff into gutters and drains carrying water quickly to the nearest river - A = after urbanization; B = before urbanization - Water runs off faster in urbanized areas |
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How might climate change modify the amount of flood damage expected over time? |
- For every 1ºF increase in temperature, the atmosphere can hold 4% more water, meaning volume of rainfall will increase when it pours |
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Why shouldn’t you fly an airplane through an ash cloud (what can ash do to a plane engine? What can it do to a plane windshield?)? |
- Ash is finely ground volcanic rock and contains tiny particles of abrasive glass, sand, and rock that pose serious danger to aircraft engines and structures - Cockpit: Obscured vision - Corrosion: Damage to plastic, rubber and metal components from gases (such as SO2) - Engines: Ash deposits melt and clog interior, blocking fuel nozzles and restricting airflow, resulting in loss of thrust or failure - Cabin: Air quality impaired - Instruments: Ash blocks pitot tube, used to measure airspeed; aircraft could stall if pilot does not know how fast it is going - Turbine blades eroded, leading to reduction in performance |
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What earth process causes volcanism? |
Tectonic process causes volcanism |
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What can we infer the properties of, based on lavas (what do they tell us about that we otherwise cannot observe)? |
We use samples of lavas from volcanoes to infer properties of the Earth’s interior |
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How deadly are volcanoes, relative to the other hazards we have discussed this semester, and how frequent are volcanic eruptions? |
- Out of earthquakes, tsunamis, floods/meteorological/climate, and landslides/mudflows, volcanoes cause least amount of fatalities (less than 363 from 2004-2013) - Earthquakes and tsunami - 650,321 - Floods/meteorological/climate - 328,580 - Landslides/mudflows - 9,012 - Volcanoes - 363 - Average of 55 volcanoes erupt each year |
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Magma |
Hot fluid/semifluid material below or w/i earth’s crust |
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Lava |
Molten rock on the surface that cools into volcanic rock |
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Volcanic hazards |
1. Lava flows 2. Pyroclastic flows and pyroclastic surges 3. Fallout and ballistics 4. Lahars and debris avalanches 5. Degassing |
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Volcanic hazards - Lava flows |
- Melted rock (temps up to ~2,400ºF) - Flows can move at velocities as high as 100 km/hr (60 mph) or as low as m/day |
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Volcanic hazards - Pyroclastic flows and pyroclastic surges |
- Pyroclastic flow: Dense collection of fragments and gases from a volcanic eruption that flows down the slope of a volcano - Pyroclastic surge: Low-density flow of volcanic material with a higher proportion of gas to rock |
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Volcanic hazards - Fallout and ballistics |
- Deposits can be many meters deep near volcano - Volcanic “bombs” can be car sized + |
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Volcanic hazards - Lahars and debris avalanches |
Volcanic mudflows
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Volcanic hazards - Degassing |
- Gases released during eruption - Local - Suffocation and lung damage - Global - Climate change |
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Nyiragongo 1977 |
- 70 ppl dead - Set of fissures opened up on the volcano’s flanks b/w 2700 and 2200 m altitude - 22 million cubic meters of lavas erupted (drained lava lake) - 60 mph lava flows - Parts of Goma destroyed |
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Nyiragongo 2002 |
- Fracture opened on volcano’s flanks b/w 2800 and 1700 m elevation - 20-30 million cubic meters of lavas erupted - 10k homes destroyed - 400k ppl displaced - 147 ppl killed by CO2 asphyxiation, fires, building collapse b/c of earthquakes - 15% of Goma destroyed |
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Mount St. Helens |
- May 19, 1980 - Lateral blast and pyroclastic surge - Magma buildup caused huge bulge - Caused entire N face to slide away, creating the largest landslide recorded - Eruption column of 80k ft - Glaciers on the volcano melted forming lahars - 57 ppl dead |
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Mr. Vesuvius |
- Eruption in AD 79 - Mt. Vesuvius is a stratovolcano in Gulf of Naples, Italy - Eruption led to the burying/destruction of Roman cities (e.g. Pompeii) - Ejection cloud 33km high - 16k dead |
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How does pahoehoe lava differ from a’a lava? WHY do the two types of lava differ (what properties change)? |
- Pahoehoe: Fluid, flowing ropy texture - A’a’: Clinkery, jagged blocks - Flow can transform from pahoehoe to a’a’ with loss of gas and temperature, increasing viscosity |
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Pillow lava |
- Lava that has solidified as rounded masses, characteristic of eruption under water - Lava erupted under or flowing into water - Outer skin quenches rapidly to glass |
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Viscosity |
Ability of a substance to resist flow |
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What 3 factors interact to determine the viscosity of magmas/lavas? |
1. Temperature (higher temp = lower viscosity) 2. Composition 3. Gas content |
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How does gas content determine viscosity of magmas/lavas? |
- Magmas contain significant contents of H20, CO2, SO2, and other gasses at high pressure - Dissolved gases exsolve when magmas rise to lower pressure - Vesiculation (bubbles that form) results from gas exsolution which dramatically increases volume of magma - Driving force of explosive eruptions |
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How does silica content modify viscosity, and why? |
- Higher silica content = higher viscosity (b/c less of the magma is melted) - The higher the Si content of a magma, the more polymerized the melt, increasing “internal friction” and the viscosity (more explosive eruptions) |
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Which type of magma would be more viscous, basaltic or rhyolitic magma, and why? |
- Rhyolitic would be more viscous (high gas content, low temperature, and high silica content) - Basaltic magma has low viscosity b/c it has low gas content, high temps, and low silica content |
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How does the addition of water to magma modify its viscosity? |
- Dissolving water in magma decreases viscosity - Rhyolites has high viscosity, and water has high effect on them |
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How do gases drive explosive eruptions? |
- Explosivity depends on whether gas can escape easily (fluid lavas) or is trapped in vesicles and pressure builds up in the magma (viscous magmas) |
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How does gas content relate to viscosity (given the exact same gas content, would a fluid lava or a viscous lava produce a more violent eruption)? |
- More viscous lavas = more violent eruption |
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What does it mean for a rock to be vesicular? |
- Vesicular texture is a volcanic rock texture characterized by a rock being pitted w/ many cavities (known as vesicles, which are bubbles formed from gas escaping) at its surface and inside - More vesicular = lower viscosity (b/c gas can expand easily in more liquid lavas) |
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Volcanic Explosivity Index (VEI) |
- Relative measure of the explosiveness of volcanic eruptions - A “0” is given for non-explosive eruptions (defined as less than 10k m3) - An “8” is given to the largest volcanoes in history - Logarithmic scale, with each interval on the scale representing a 10x increase in observed ejecta criteria (w/ exception of b/w VEI 0, 1, and 2) - Ranks increase as volume of material associated with the explosion increases |
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Know the relative ranks, in terms of the VEI, of Hawaiian, Strombolian, Vulcanian, Plinian, and Ultra-Plinian eruptions |
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What type of eruption is associated with fire fountains? |
Hawaiian |
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What type of eruption is associated with bubble pops? |
Strombolian |
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What type of eruption is associated with short-term vigorous explosions? |
Vulcanian |
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What type of eruption is associated with eruption columns and pyroclastic flows? |
Plinian |
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What are the different types of pyroclastic materials and how do we classify them? |
- Pyroclastic materials are classified by size (composition doesn’t matter) - Ash (<2mm) - Lapilli (2 to 64 mm) - Bombs and blocks (>64 mm) |
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What sort of hazard does volcanic ash pose to you, if you live close to a volcano and breathe it in a lot? |
- Respiratory problems - Eye irritation (esp. contact lenses) - Skin irritation - Death by roof collapse - Death by auto accidents - Silicosis - lung fibrosis caused by the inhalation of dust containing silica |
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Pyroclastic flow |
- Dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and flowing downslope at great speed - More dense, rocky soup flowing downhill |
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Pyroclastic surge |
- Fluidized mass of turbulent gas and rock fragments which is ejected during some volcanic eruptions - Less dense, turbulent cloud of gray ash and gas |
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How do pyroclastic flow differ from a pyroclastic surge? How do they rank in terms of deadliness? |
- Flows and surges have different gas concentrations - Most deadly of all volcanic phenomena |
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Mt. Pelee |
- May 8, 1902 - Killed 26k ppl, largest amount of casualties for volcanic eruption this century - Pyroclastic flow - Volcanic gases and dust w/ temps ~805ºC ignited everything flammable in city |
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What are the different parts of an eruption column (anatomy)? |
- Gas thrust region: Lower column, driven by gas expansion - Convective thrust: Upper column, driven by constant release of thermal energy from internal ash - Umbrella region (a.k.a. downwind plume) and fallout: Top of eruption column |
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Pyroclastic fall deposits |
Formed from material explosively ejected from the vent |
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Pyroclastic flow deposits |
Gravity-controlled surface flows which travel as high particle concentration gas-solid dispersions |
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Pyroclastic surge deposits |
Gravity-controlled surface flow which travels as expanded, turbulent low particle concentration gas-solid dispersion |
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Lahar |
Volcanic mudflow |
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What happened at Nevado del Ruiz in Colombia? What made this tragedy so deadly? |
- Year of minor earthquakes - November 13, 1985 - Red Cross had called for an evacuation, then called it off, and then the pyroclastic eruption occurred and the storm obscured volcano summit - Lahar killed 23k |
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Where in the United States are we building on lahars? |
- Mt. Rainir - 300k+ ppl live in the area covered by the 50 major lahars that have occurred over the past 10k years |
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What happened at Lake Nyos in Cameroon, and why? How are people attempting to mitigate a future catastrophe? |
- Crater lake (produced by eruption ~500 ybp) - Magma degasses CO2 into bottom of lake, which is density stratified - CO2 reaches saturation in lower lake - Overturning causes massive degassing - CO2 erupted from lake (Limnic eruption) - denser than air flowed down valleys - 1.7k dead |
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Know the details about Tambora’s big eruption-how did this impact climate globally? What were the effects on people living both nearby and far away? How does the scale of this eruption compare to what might happen if Yellowstone erupted? |
- April 5-11, 1815 - Greatest historic eruption - VEI 7 - Blast heard > 1.6k miles away - 100 km3 (24 mi3) of lava erupted - Measurable ash fell 800 miles away - Eruption column 28 miles high - Lost 4.7k ft of elevation - 80-90k dead (11k directly, more from famine and disease) - “Year without a summer” - If Yellowstone erupted: 600 km3 of molten rock - Yellowstone comparison: Yellowstone was a VEI 8 and Tambora was VEI 7 |
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What are our two examples of flood basalt volcanism, and how do they impact climate? |
Laki and Deccan Traps |
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Laki |
- 1783 - 15 km3 basalt erupted from fissure - Flooded 565 km2 - 200 megatons of aerosol, H2SO4 emitted and other gasses (particularly HF) - Plume (of gas, no ash) rose ~ to Tropopause and dispersed - Effect on climate: Acid rain harmed vegetation, fluorine poisoning killed grazing animals in Iceland, 20% of Iceland’s population died; 20k deaths in England (caused by famine resulting from reduced vegetation), N. Hemisphere cooling for ~3 years of ~2ºC |
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Deccan Traps |
- India and seychelles plateau ~65 million years ago - 1,300,000 km3 of basalt - Effect on climate: Decades long periods w/ 10x amount of CO2 and SO2 released each year compared w/ Laki eruption, Ocean acidification, Global warming, Played role in K-T mass extinction |
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What sorts of gases that are released during volcanic eruptions, and what are their impacts? |
- Volcanic eruptions emit water vapor and toxic gases into atm - CO2, SO2, hydrogen sulfide, hydrochloric acid, carbon monoxide - Impacts: Kill humans, Global warming/cooling, Erode buildings |
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Cinder cone volcanoes |
- Pyroclastic material - rock or magma erupted explosively and deposited as particles (e.g. cinder or scoria) - Constant slope - Particles erupted explosively and come to rest at angle of repose (steepest angle at which a sloping surface formed of a particular loose material is stable) (~35º - unconsolidated debris stability) - Short-lived and easily eroded - Smallest volcano size |
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Shield volcanoes |
- Built by successive flows from central vent and fissure zones - Fluid basalt lava travels long distances - Creates a broad, shield-shaped edifice many 10’s of km in circumference - Pose tsunami hazard Largest volcano size - E.g. Haleakala, Maui, Hawaii |
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Composite volcanoes / Stratovolcano |
- Erupts lava flows and explosive pyroclastic material - Capable of explosive and effusive eruptions - Medium volcano size - Broad, shallow outer flanks w/ steep and conical side - E.g. Mt. Shasta, Mt. Fuji, Vesuvius |
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How can a shield volcano create a tsunami hazard? |
Shield volcanoes pose tsunami hazard because of the possibility of flank failures, which can be caused by erosion, gaseous pressure |
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What determines eruption style and type of volcano formed? |
Magma viscosity and volume |
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How does viscosity and silica content relate to the landforms that are made by different types of volcanoes, and how does this all relate to plate tectonic settings? |
- Chemical composition (including gas content) and temperature control viscosity - Temperature, silica content, and volatile/moisture content control viscosity |
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What are the three different ways by which we can generate melt? Which of these processes occurs at a mid ocean ridge? Which occurs within a mantle plume? |
- Add water (fluid induced) to mantle (E.g. subduction zones) - Increase temperature (thermal) (E.g. continental crust) - Decrease pressure on mantle (decompression) (E.g. mid-ocean ridges, mantle plumes) |
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How do we generate melt at subduction zones? |
- Water is carried into the hot mantle in the subducting oceanic crust - The water is released into the hot mantle rock above the subducting lithosphere/crust, which causes it to partially melt |
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How do we generate magma in mid ocean ridge settings? |
Decrease pressure on mantle (decompression) |
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What proportion of currently active volcanoes have claimed lives? How many volcanoes are active worldwide? |
- 500 active volcanoes - 1 in 6 has claimed lives |
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How do we mitigate volcanic hazards? |
- Land use planning - Monitoring for early warning: gas, geodesy, and seismicity - Have an effective strategy in place to react to eruptions before it happens |
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Climate |
Long-term pattern of weather in an area |
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Weather |
Short-term (minutes-to-months) changes in the atm |
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What factors interact to drive climate at a local level? |
1. Latitude 2. Proximity to large bodies of water 3. Elevation 4. Topography |
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How does latitude interact to drive climate at a local level? |
- Determines incoming solar insolation (how much sunlight is reaching Earth) - Places at high latitudes (far from equator) receive less sunlight than places at low latitudes (close to equator) - Amount of sunlight and amount of precipitation affects the types of plants and animals that can live in a place |
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How does the proximity to large bodies of water interact to drive climate at a local level? |
- Ocean is big heat sink and moderates temperature of lands - Stabilizes climate - Warm currents can heat high latitudes |
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How does elevation interact to drive climate at a local level? |
- In high elevation, climate is tundra like with heavy vegetation - Effects plant and animal distribution - Increase in elevation = decrease in temperature |
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How does topography interact to drive climate at a local level? |
- Orography - Rain shadows - Mountains can be barriers to wind - Valleys tend to be warmer than surrounding flatlands |
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What factors interact to drive climate at a global level? |
- Changes in incoming solar insolation (how much sunlight is reaching Earth) - Configuration of continents - Changes in albedo (how much sunlight is reflected back to space) - Changes in atmospheric composition - Milankovitch cycles (Orbital parameters, How the orbit of the earth has changed, How the poles have wobbled, Changes the insolation) |
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How does the configuration of continents impact global climate? |
- Where the continents are drives where the currents are on the ocean - Continents over poles drive cooling |
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What is albedo, and what does it mean to have a high or a low albedo? |
- Albedo: how much sunlight is reflected back into space; measure of reflectivity on earth - High albedo means that a lot of light is being reflected (e.g. snow) - Low albedo means that NOT a lot of light is being reflected (e.g. oceans and forests absorb sunlight) |
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Which greenhouse gases vary the most in their concentration? |
Water vapor > carbon dioxide (CO2) > methane (CH4) > nitrous oxide (NO2) > fluorinated gases would be no water or life |
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How does the greenhouse effect work? |
- Sunlight hits earth, some is reflected b/c of albedo and some is absorbed by earth. Earth re-emits the absorbed sunlight as infrared. Some of the reemitted sunlight is absorbed by greenhouse gases and hold onto infrared radiation/heat - We need the greenhouse effect b/c without it the surface temp would be -18ºC (-8ºF), there |
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CO2 sinks? |
- Weathering rock - Green plants (especially tropical rainforests) - Ocean - Coral reefs |
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CO2 sources? |
- Volcanoes - Combustion of fossil fuels - Metamorphism - Animal cultivation |
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What are oil/natural gas/coal made of? |
Once living organisms |
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Combustion |
- Process of burning something - Released trapped organic material |
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What general observations can we make about past global climate drivers (what has made the Earth cold in the past, and when has it been warm?)? |
- Continents at poles - Major changes in CO2 - Snow and ice accumulate - increase albedo - We get cold |
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How far south did glaciers reach in North America during the last major cold period on Earth (i.e. the Laurentide Ice Sheet, 18,000 to 14,0000 years ago)? |
Laurentide Ice Sheet took up most of Canada and a large portion of the N U.S. |
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What has driven cyclicity in the most recent ice age? |
- Milankovitch Cycles: Long term variations in the orbit of the Earth which result in changes in climate over long periods of time and are related to ice age cycles - Eccentricity, Tilt, Precession (wobble) |
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Eccentricity |
Earth encounters more variation in the energy that it receives from the sun when Earth’s orbit is elongated than it does when Earth’s orbit is more circular |
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Tilt |
The tilt of Earth’s axis varies b/w 22.2º and 24.5º. The greater the tilt angle is, the more solar energy the poles receive |
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Precession (wobble) |
A gradual change/wobble in the orientation of Earth’s axis affects the relationship b/w Earth’s tilt and eccentricity |
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Positive feedback cycles |
- Amplify warming and cooling trends - E.g. growing ice caps increasing albedo |
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Negative feedback cycles |
- Provide checks and balances on warming and cooling - E.g. CO2 increasing the growth of forests |
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What are some of the various sources (proxies) of long-term climate records? |
- Deep sea sediments - Ice cores |
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What three types of information can we get from ice cores, and how is this material preserved? |
- Atmospheric composition (i.e. CO2, Methane) - Temperature (from oxygen isotopes) |
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How is atmospheric CO2 related to temperature? |
Positive correlation (increasing CO2 correlates to increasing temperature) |
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Current CO2 concentrations in the atmosphere are approximately 405 ppmv. How far back in time were values this high in the atmosphere? |
15 million years ago |
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What is driving (primarily) increased concentrations of greenhouse gases in the atmosphere? |
- Human influences - Combustion |
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What are two major sources of methane? |
- Enteric fermentation - Natural gas systems |
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What percentage of greenhouse gases are absorbed by oceans and forests? |
55% |
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How do we predict the future impacts of climate change? You should know GCMs (what they are, and what we are trying to figure out when we use them). |
General Circulation Model (GCM): Employs a mathematical model of the general circulation of a planetary atmosphere or ocean |
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What is future climate change going to look like for Iowa? What about for the rest of the country? |
- Temperature will increase - Lower emissions scenario: 3ºF by 2040 & 5ºF by 2080 - Higher emissions scenario: 4ºF by 2040 & 10ºF by 2080 |
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How has global climate change affected the arctic? |
- The poles are heating more rapidly - Ocean water (usually insulated by ice) warms more in summer and releases more heat to the atmosphere in the winter (lower albedo) |
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What are some of the general anticipated impacts of climate change? |
- Sea level rise - Increase in temperature - Faunal changes - Ocean acidification |
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Why does climate change lead to ocean acidification? |
When the ocean absorbs CO2 makes carbonic acid, pH is lowered (ocean acidification) |
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What are some of the biotic impacts (impacts on animals) of climate change? |
- Coral bleaching - Shifts in ranges of species - Shifts in ranges of disease vectors - Extinction of less resistant species (it will be hard to adapt) - Extinction of species at the poles (there’s no where to go) |
