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64 Cards in this Set
- Front
- Back
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THE BIOSPHERE Stratigraphy |
a thin “layer” of life on Earth’s surface- composed of ecosystems Study of the layers of rock (strata) |
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Biostratigraphy |
Part of stratigraphy that identifies the relative ages of rock layers using fossils |
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PRINCIPLE OF SUPERPOSITION |
IN LAYERED STRATA (SEDIMENTARY ROCKS, LAVA FLOWS) “WHAT’S ON TOP IS YOUNGEST” |
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PRINCIPLE OFORIGINAL HORIZONTALITY |
IF IT’S TILTED OR FOLDED, IT WAS ORIGINALLY FLAT” |
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PRINCIPLE OF LATERAL CONTINUITY |
“IF IT’S HERE IT’S PROBABLY OVER THERE TOO” |
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PRINCIPLE OFCROSS-CUTTING RELATIONSHIPS |
“IF IT CUTS THROUGH, IT IS PROBABLY YOUNGER |
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UNIFORMITARIANISMJAMES HUTTON |
the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere in the universe |
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A cross-cutting UNCONFORMITY Tilted sedimentary rocks originally deposited whilleeeee vertical sedimentary rocks |
a period of non deposition or active erosion a cross cutting unconformity is an example of a cross cutting relationship in a DESERT ~ contain marine fossils deposited in a DEEP ocean |
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siccar point geological history (6 steps) |
1.Silurian: Sediments deposited in deep ocean; Then converted to rock at depth 2.Tectonics fold rocks at depth 3.Uplift, exposure and erosion of rock forms erosion surface 4.Devonian: Deposit desert sediments; Forms angular unconformity with folded rocks 5.Desert sediments converted to rock at depth; Tectonics tilt all strata 6.Uplift and erosion form current exposure of Silurian and Devonian rocks at Siccar Point |
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RINCIPLE OF FAUNAL SUCCESSION WILLIAM SMITH |
Fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances |
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BEST CONDITIONS TO PRESERVE FOSSIL SPECIES FOR BIOSTRATIGRAPHY (4) |
1. SHORT fossil range = higher RESOLUTION 2. Common 3. Lived in environments where fossilization is likely to occur 4. Present in many different environments |
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AMMONITES (400-66 MYA) |
a commonly used fossil from the Mesozoic |
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FIVE MAJOREXTINCTION EVENTS |
•End of Cretaceous •Late Triassic •Permo / Triassic (big one) •Late Devonian •Late Ordovician |
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James Ussher (1581 - 1665) Archbishop of Armagh claimed the earth was how old? George Cuvier1800s proved what?? |
•Adds up all dates in Bible •Concluded that Earth was 6,000 years old •And was created on October 22, 4004 BC proved that extinction of animals had occured |
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Halysites |
an extinct type of coral that lived from Ordovician to Silurian (449.5 to 412.3 mya) |
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THE GEOLOGICAL TIME SCALE |
•Many divisions based on extinction events•ESPECIALLY the 5 major events of the Phanerozoic which “bracket” these divisions•Compare the Precambrian to the Phanerozoic |
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youngest to oldest geological time scale |
Clowns- Cambrian Only -Ordovician Shoot -Silurian Ducks -Devonian Carrying- Carboniferous People -Permian That -Triassic Just -Jurassic Can’t- Cretaceous Play- Paleogene Quietly -Quaternary |
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The Precambrian is Current extinction rate is approximately |
87% of Earth’s history 100 extinctions per million species per year |
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RADIATION OF NEW SPECIES= First appearance of species |
BASE OF NEW GEOL. TIME PERIODS / GROUPS OF PERIODS help geologists define start of new period |
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WHAT DEFINES A MASS EXTINCTION EVENT? |
At least 30% of species lost |
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CAUSES OF MASS EXTINCTIONS- biological reasons |
Biological•Competition•Predation•Pathogens•Biogeology mosses may have caused Late Ordovician ice age (and ensuing species extinction)è break down rocksè increase CO2 absorptionè global T decreaseè break down rocksè more nutrients to oceanè phytoplankton bloomsè anoxia due to O26 consumed by decomp |
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causes of mass extinctions-Physical (Earth-based) |
• Changes in continental configuration causes changes in: climate ocean cycles sea level Example:Late OrdovicianExtinction whenGondwana movestowards the SouthPole |
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THE GREATER THE LANDMASS |
THE LOWER THE BIODIVERSITY NOTE: This is true for marine as well as land based creatures |
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CAUSES OF MASS EXTINCTIONSSUMMARY |
1. Biological–Extinctions, but generally not massive 2. Physical (Earth-based)–Gondwana glaciation–Pangea supercontinent–Atmospheric/volcanism3. Extraterrestrial-based 4. Combo of above factors |
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PERMO/TRIASSIC EXTINCTION JUST A BAD DAY FOR THE BIOSPHERE PERMO/TRIASSIC EXTINCTION, 251 mya CAUSES? |
1. Continental configuration: Supercontinent, drop in diversity• Less ecological niches leads to less diversity 2. Sea level fall - less ocean ridge activity 3. Oceanic stagnation• anoxia (lack of O2)• Polar waters unable to sink, no ocean circulation4. Possible extra terrestrial impacts 5. Climate Change• Siberian Traps (massive volcanic activity)2-3 million km3 basaltic lava formsè high CO2 in atmosphere |
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were green house gases a factor in 250 mya as well? |
• CO2 in atmosphere causes Greenhouse warming • Raises global temperature by 5°C |
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PERMO - TRIASSIC EXTINCTIONmore greenhouse gas issues: CLATHRATES |
Clathrate: solid crystal structure containing methane (CH4) from decay of organic material, common in deep ocean sediments Ocean warms -melts clathrates - releases CH4 Methane is an even better greenhouse gas than CO2 Add 5°C increase in global temperature: now 10 °C warmer! |
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many creatures gone: |
clears “ecological space” A new type of reptile evolves during the Triassic and takes advantage of this… The Dinosaurs ecological space » ecological niche |
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65 million years ago NOT JUST TERRESTRIAL SPECIES |
end of cretaceous At least 50% of ALL species lost• On Land: nothing over 25kg survives Marine fauna suffers:ammonites / marine reptiles• 80 - 90% marine species lost |
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WALTER AND LUIS ALVAREZ thought |
mass extinction at K/Pg (65 mya) was caused by the impact of a LARGE ASTEROID because iridium was found in a layer of strata and the best source of iridium is found in comets/meteors |
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further evidence to support ALVAREZ HYPOTHESES: SIGNIFICANCE? |
1. Ferns spores dominate sediment samples at K/Pg boundary Ferns are first to colonize fire-impacted landscape. Spores act as a “proxy” for forest fires. AFTER IMPACT: MASSIVE “SPIKE” IN % OF FERN SPORES IN SEDIMENTS |
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FURTHER EVIDENCE TO SUPPORT ALVAREZ HYPOTHESES:Soot |
2. Soot layers associated with the iridium layer SIGNIFICANCE? Evidence of massive global fires |
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FURTHER EVIDENCE TO SUPPORT ALVAREZ HYPOTHESES: Tektites |
3. Tektites common at K/Pg boundaryTektites: natural glass; produced by melting rocks during impact11SIGNIFICANCE? Evidence of a very large impact event |
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FURTHER EVIDENCE TO SUPPORT ALVAREZ HYPOTHESES: Shocked Quartz |
common at K/Pg boundarycross-hatched lines(shock lamellae):stress lines in the quartz crystal due to impact SIGNIFICANCE? Evidence of a very large impact event |
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FURTHER EVIDENCE TO SUPPORT ALVAREZ HYPOTHESES: |
5. Tsunami depositsfound around much of the globe corresponding to K/Pg boundary SIGNIFICANCE?Meteor impactor hit water, excavated a crater from the rock beneath that sea, causing a tsunami. |
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FURTHER EVIDENCE TO SUPPORT ALVAREZ HYPOTHESES:6. The Crater:The Smoking Gun |
Drilling off coast of Yucatan Peninsula, Mexico reveals odd rocks20 km from impact site 50 km from impact site SIGNIFICANCE? “odd rocks” are suevite, a breccia (fractured rock) formed during impact events |
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EOPHYSICS REVEALS A CRATER NEAR THE YUCATAN PENINSULA, MEXICO |
• Chicxulub Impact Crater• 180 km across•thick layers of tsunami deposits, shocked quartz and tektites•thicker towards crater |
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SEISMIC REFRACTION ‘TOMOGRAPHY’ (USING P AND S WAVE SPEED |
shows changes in density of ocean bottom over large areasimages indicate sediments have filled in a very large crater |
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CRATER STRUCTURE of Chicxulub Crater |
very typical of large complex cratersComplex crater• concentric ringed structure• central peak or peak ring |
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CHICXULUB IMPACT: INITIAL EFFECTS |
• vaporizes everything close by• widespread forest fires • global tsunami |
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CHICXULUB IMPACT: SHORTER TERM EFFECTS (MONTHS) after dust clears |
Sunlight blocked out• nuclear winter• weeks to several months• NO photosynthesis stops on land and in oceans water vapor remains in the atmosphere• greenhouse effect is enhanced |
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CHICXULUB IMPACT:SHORT TERM EFFECTS (YEARS) SHORT TERM EFFECTS (YEARS) |
Yucatan limestones are vaporized: CaCO3 -> CO2 •increased CO2in atmosphere •increased greenhouse effect • average global temperature increased by 10°C |
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CHICXULUB IMPACT:LONGER TERM EFFECTS |
Rapid shift in environmental conditionsCold House (months) => Hot House (years to decades) global volcanic activity may have increased 2-fold increased CO2 and SO2 in atmosphere(both are potent greenhouse gases) •increased global temperature •increased pressure on ecosystem survival High energy blast affects Earth’s atmosphere nitrogen and oxygen combine to forms Nitrogen oxides (NOX) •NOX + water vapor -> acid rain! • oceans and soils are acidified |
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longer term effects- Evaporites also how is the food chain affected: |
Salts precipitated by evaporating bodies of water Some evaporite minerals are rich in sulfates like gypsum.Meteor blast vaporized these evaporites, adding SOX to the atmosphereResult: acid rain Base of the food chainin oceans and on landare strongly affected |
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OTHER POSSIBLE CAUSES OF THEK/Pg EXTINCTION? |
formation of Deccan Traps, India (flood basalts) causes •acid rain •ozone depletion •climatic greenhouse effects |
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COMPLEX COMBINATION OF FACTORS |
•Continuing environmental degradation related to break up of Pangaea •Many species were already going into extinction •However, dinosaurs appear to be OK right up to impact |
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he K/Pg saw the extinction ONLY |
of the non-avian dinosaurs |
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SUMMARY EFFECTS OF K/Pg IMPACTOR Initial, long term, longer term |
Initial effects (days) •fireball & vaporization • widespread forest fires • nearly global tsunamiLong term (months)•sunlight shut off • photosynthesis stops on land and in oceansLonger term (decades) •lots of water vapor and CO2 in atmosphere (greenhouse gases) • water + NOX and SOX -acid rain |
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Define- Asteroid meteoroid comet |
-Very large (> 10 m) rocks in space; smaller than a planet -smaller (< 10 m) rockso“Meteors” as they enter Earth’s atmosphereo“Meteorite” if it survives entry to Earth’s atmosphere. -Rock MIXED with ice Near Sun, has a “tail” of gas and dust particles |
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COMETS COME FROM THE |
OORT CLOUD and KUIPER BELT |
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ASTEROIDS COME FROM |
A SERIES OF BELTS BETWEEN MARS AND JUPITER |
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Early Earth probably suffered multiple impacts but |
Craters eroded over time until the 1960s craters on the earth were deemed improbable and moon craters were deemed extinct volcanoes |
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Gene Shoemaker’s hypotheses |
sudden geologic changes arise from asteroid strikes • asteroid strikes are common over geologic time periods • Impact craters form large circular structures associated with ejecta, shocked quartz, iridium, etc. |
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• One of the oldest known impact craters (Late Triassic) is found in |
MANICOUAGAN CRATER, NORTHERN QUEBEC Occurred at SAME time as other impacts! 1. Saint Martin Crater, Manitoba (d=100 km) 2. Rochechouart Crater, France(d=25 km) |
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DO THEY COME FROM THE SAME SOURCE? |
If continents were reassembled to late Triassic times • All craters line up along 22.8°N latitude, over distance of 4,462 km • Significance:Impacts of fragmentedcomet/asteroid? |
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PERIODICITY OF MASS EXTINCTIONS |
26-30 million year “Extinction cycles” |
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gravitational kicks from |
1) Nemesis - companion to our Sun• Red dwarf star - smaller, cooler than our Sun• Black hole? 2) “Planet X” beyond Neptune 3) Moving through the Galactic Plane |
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Torino Scale |
Communicates potential threat on scale of 0 – 10 • Assesses the risk of Near Earth Objects (NEO) |
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SPACEGUARD SURVEY |
Surveys NEOs • Survey all asteroids >1 km • Was ~80% complete in 2008 • Smaller objects not tracked; All much larger objects tracked • Track those that have mass extinction potential |
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PROPOSED MITIGATION STRATEGIES |
1. Fragmentation• Blow it up! • Would have to DRILL into object to be effective • Risky: difficult to predict - multiple impact risk • Would need to land on the impactor |
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2. Sudden Orbit Adjustment |
• Requires warning period • Methods: Explode nuclear warhead smash projectiles into asteroid / comet surface |
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3. Steady State Orbit Adjustment |
Requires warning period but more predictable • May use chemical, electric or nuclear propulsion • Mass drivers - excavate and accelerate material awayfrom asteroid |
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4. Ablation systems |
Irradiate surface with laser or focus sunlight from large mirrors • Would need to put satellite into orbit around the impactor (we’ve done this too!) |
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5. Riding the solar winds |
• Install solar sails (mirrors) or coat asteroid with high reflectivity material • Requires LONG warning period |
