NSCI 314

LIFE IN THE COSMOS

5 – FOSSILS AND RADIOACTIVE DATING AND

GEOLOGY AND THE ORIGIN OF THE EARTH

Dr. Karen KolehmainenDepartment of Physics

CSUSB

Course website:http://physics.csusb.edu/~karen/

TYPES OF ROCKS IGNEOUS: MADE FROM MOLTEN ROCK (FROM A

VOLCANO) THAT COOLED AND SOLIDIFIED.

SEDIMENTARY: MADE FROM SEDIMENTS THAT ARE DEPOSITED AND COMPRESSED GRADUALLY, USUALLY AT THE BOTTOM OF A BODY OF WATER. DEEPER LAYERS ARE OLDER, TOP LAYERS ARE YOUNGER.

METAMORPHIC: MADE FROM ROCK THAT HAS BEEN HEATED (BUT NOT ENOUGH TO MELT IT) AND/OR COMPRESSED ENOUGH TO CHANGE ITS STRUCTURE.

NOTE THAT ONE TYPE OF ROCK CAN CHANGE INTO ANOTHER TYPE VIA MELTING, EROSION, COMPRESSION, HEATING, ETC.

ROCKS AND MINERALS ROCK TYPES (IGNEOUS, SEDIMENTARY,

AND METAMORPHIC) ARE BASED ON HOW THE ROCK IS FORMED, NOT ITS CHEMICAL COMPOSITION.

THE TERM MINERAL IS USED TO SPECIFY CHEMICAL COMPOSITION.

IN A PARTICULAR ROCK (OF ANY OF THE THREE TYPES), THERE MAY BE CRYSTALS OR GRAINS OF VARIOUS DIFFERENT MINERALS PRESENT.

FOSSILS RELICS OF ANCIENT ORGANISMS THAT HAVE BEEN PRESERVED

IN SEDIMENTARY ROCKS, INCLUDING:

– HARD COMPONENTS (BONES, TEETH, SHELLS, ETC.) OF ORGANISMS (THE SOFT PARTS DECAY MORE EASILY)

– MINERALS THAT HAVE REPLACED DECAYED OR DECAYING ORGANIC MATERIAL, RETAINING THE SHAPE OF THE ORGANISM (FOR EXAMPLE, PETRIFIED WOOD)

– CORPSES PARTIALLY PRESERVED BY BEING SEALED IN AN ENVIRONMENT THAT LIMITS DECAY (FOR EXAMPLE, ICE, AMBER, MATERIAL AT THE BOTTOM OF SOME SWAMPS)

– PRESERVED INDICATION OF ORGANISM’S BEHAVIOR (FOR EXAMPLE, DINOSAUR FOOTPRINTS)

MORE ON FOSSILS ONLY A TINY FRACTION OF ORGANISMS BECOME

FOSSILIZED WHEN THEY DIE. MOST ORGANISMS DECAY COMPLETELY INSTEAD OF FOSSILIZING.

FOSSILS OCCUR ONLY IN SEDIMENTARY (NOT IGNEOUS OR METAMORPHIC) ROCKS.

SINCE SEDIMENTARY ROCKS FORM LAYERS OF DIFFERENT AGES, DEEPER FOSSILS ARE OLDER.

THIS FACT IS USED TO ESTABLISH RELATIVE AGES (WHICH IS OLDER) BUT CANNOT GIVE ABSOLUTE AGES (HOW MANY YEARS AGO).

THE FOSSIL RECORD IN ANY ONE LOCATION IS INCOMPLETE BECAUSE SEDIMENTS WERE DEPOSITED THERE ONLY FOR SOME INTERVAL OF TIME.

THE FOSSIL RECORD CAN BE PIECED TOGETHER BECAUSE ROCKS IN VARIOUS LOCATIONS OVERLAP IN THEIR PERIODS OF DEPOSITION.

HOW IS THE ABSOLUTE AGE OF A ROCK OR FOSSIL DETERMINED?

RADIOACTIVE DATING

TO UNDERSTAND HOW, WE MUST FIRST UNDERSTAND THE NATURE OF RADIOACTIVITY.

TYPES OF RADIOACTIVITY ALPHA DECAY

– A 4He NUCLEUS (2 PROTONS + 2 NEUTRONS) IS EJECTED FROM A LARGE NUCLEUS.

BETA DECAY– A NEUTRON CHANGES INTO A PROTON, CAUSING AN

ELECTRON TO BE CREATED AND EJECTED FROM THE NUCLEUS, OR…

– A PROTON CHANGES INTO A NEUTRON, ACCOMPANIED BY EITHER CREATION AND EJECTION OF A POSITRON (ANTIPARTICLE OF THE ELECTRON) OR THE CAPTURE OF A ELECTRON BY THE NUCLEUS

GAMMA DECAY– PROTONS AND NEUTRONS REARRANGE THEMSELVES INSIDE

THE NUCLEUS, CAUSING A HIGH ENERGY PHOTON (GAMMA RAY) TO BE CREATED AND EJECTED FROM THE NUCLEUS.

NOTE: IN BOTH ALPHA AND BETA (BUT NOT GAMMA) DECAY, THE DAUGHTER NUCLEUS IS A DIFFERENT ELEMENT THAN THE PARENT NUCLEUS (SINCE THE NUMBER OF PROTONS HAS CHANGED).

MORE ON RADIOACTIVITY CERTAIN ISOTOPES OF CERTAIN ELEMENTS ARE RADIOACTIVE

(WILL UNDERGO RADIOACTIVE DECAY), WHEREAS OTHERS (STABLE ISOTOPES) ARE NOT.

RADIOACTIVE DECAY IS A RANDOM PROCESS (LIKE THE FLIP OF A COIN). WE CAN’T PREDICT EXACTLY WHEN A RADIOACTIVE NUCLEUS WILL DECAY, ONLY ITS PROBABILITY OF DOING SO WITHIN A CERTAIN INTERVAL OF TIME.

FOR A SAMPLE OF MATERIAL CONTAINING A LARGE NUMBER OF RADIOACTIVE NUCLEI, WE CAN PREDICT APPROXIMATELY HOW MANY OF THEM WILL DECAY WITHIN A CERTAIN PERIOD OF TIME.

THIS IS SIMILAR TO FLIPPING A COIN. WE CAN”T PREDICT

WHETHER A SINGLE FLIP WILL GIVE HEADS OR TAILS. HOWEVER, IF WE FLIP A COIN A LARGE NUMBER OF TIMES, WE KNOW WE WILL GET CLOSE TO A 50-50 MIXTURE OF HEADS AND TAILS.

HALF-LIFE THE HALF-LIFE IS DEFINED AS THE INTERVAL OF

TIME DURING WHICH A NUCLEUS HAS A 50% CHANCE OF DECAYING.

AFTER ONE HALF-LIFE HAS ELAPSED, APPROXIMATELY HALF OF THE NUCLEI IN A SAMPLE WILL HAVE DECAYED.

EACH RADIOACTIVE ISOTOPE HAS A DIFFERENT HALF-LIFE, WITH VALUES RANGE FROM A FRACTION OF A SECOND TO BILLIONS OF YEARS.

THE PROBABILITY OF DECAY DOESN’T CHANGE WITH TIME. IN OTHER WORDS, A NUCLEUS DOESN’T “REMEMBER” HOW LONG IT HAS ALREADY EXISTED WITHOUT DECAYING.

THEREFORE ANY NUCLEUS THAT HAS ALREADY EXISTED FOR ONE HALF-LIFE WITHOUT DECAYING HAS A 50% CHANCE OF DECAYING DURING THE NEXT HALF-LIFE.

HALF-LIFE EXAMPLE: CONSIDER A MATERIAL WITH A HALF-

LIFE OF 1 YEAR. LET'S SAY THAT INITIALLY, 1000 NUCLEI ARE PRESENT IN A PARTICULAR SAMPLE.

AFTER 1 YEAR HAS ELAPSED, APPROXIMATELY 500 (OR 1/2) HAVE DECAYED, AND 500 (1/2) HAVE NOT YET DECAYED. PARENT AND DAUGHTER ARE EQUALLY ABUNDANT.

AFTER 2 YEARS, APPROXIMATELY 750 (3/4) HAVE DECAYED, AND 250 (I/4) HAVE NOT YET DECAYED. DAUGHTER IS 3 TIMES AS ABUNDANT AS PARENT.

AFTER 3 YEARS, APPROXIMATELY 875 (7/8) HAVE DECAYED, AND 125 (1/8) HAVE NOT YET DECAYED. DAUGHTER IS 7 TIMES AS ABUNDANT AS PARENT.

DECAYS CONTINUE IN THIS MANNER.

RADIOACTIVE DATING COMPARE ABUNDANCES OF THE PARENT

AND DAUGHTER ISOTOPES TO DETERMINE HOW MUCH TIME HAS ELAPSED. (SINCE WHEN?)

RADIOACTIVE DATING OF A ROCK MEASURES THE TIME SINCE THE ROCK SOLIDIFIED.

FOR AN IGNEOUS ROCK, THIS GIVES THE AGE OF THE ROCK.

RADIOACTIVE DATING THE TECHNIQUE ISN’T DIRECTLY USEFUL FOR A SEDIMENTARY

ROCK (THE ONLY TYPE IN WHICH FOSSILS ARE FOUND). IF YOU DO RADIOACTIVE DATING OF A SEDIMENTARY ROCK, IT WILL TELL YOU THE ELAPSED TIME SINCE THE SMALL GRAINS INSIDE THE ROCK SOLIDIFIED, NOT THE TIME SINCE THE SEDIMENTS WERE DEPOSITED OR COMPRESSED TO FORM THE SEDIMENTARY ROCK. THUS IT WON'T TELL YOU THE AGE OF THE SEDIMENTARY ROCK OR ANY FOSSILS IN IT.

HOWEVER, IF A SEDIMENTARY ROCK LAYER IS “SANDWICHED” BETWEEN TWO IGNEOUS ROCK LAYERS, THE TECHNIQUE WILL PUT CONSTRAINTS ON THE AGE IN THE IN-BETWEEN LAYER.

FOR EXAMPLE, CONSIDER A SEDIMENTARY ROCK LAYER SANDWICHED BETWEEN TWO LAYERS OF IGNEOUS ROCK. THE LAYER OF IGNEOUS ROCK ON TOP IS 100 MILLION YEARS OLD, AND THE LAYER OF IGNEOUS ROCK UNDERNEATH IS 110 MILLION YEARS OLD. THEN THE SEDIMENTARY ROCK (AND ANY FOSSILS IN IT) IS SOMEWHERE BETWEEN 100 AND 110 MILLION YEARS OLD.

EXAMPLES OF RADIOACTIVE DATING

PARENT

URANIUM 238

POTASSIUM 40

URANIUM 235

CARBON 14

DAUGHTER

LEAD 206

ARGON 40

LEAD 207

NITROGEN 14

HALF-LIFE(YEARS)

4.47 BILLION

1.25 BILLION

704 MILLION

5730

TYPE

CHAIN*

BETA

CHAIN*

BETA

*CHAIN MEANS A SEQUENCE OF SEVERAL DECAYS (POSSIBLY OF DIFFERENT TYPES), NOT JUST A SINGLE DECAY

COMPLICATION IF SOME OF THE DAUGHTER ISOTOPE WAS PRESENT

INITIALLY, IT WILL ALTER THE RELATIVE ABUNDANCES AND GIVE AN INCORRECT AGE (UNLESS WE CAN COMPENSATE FOR THIS).

EASIEST SOLUTION: USE A DECAY PROCESS FOR WHICH THE DAUGHTER ISOTOPE IS GASEOUS AND WOULD HAVE ESCAPED FROM THE ROCK WHILE IT WAS STILL MOLTEN. THEN ANY DAUGHTER NUCLEI PRESENT MUST HAVE RESULTED FROM DECAY OF THE PARENT AFTER THE ROCK SOLIDIFIED. (THEN THE GAS IS TRAPPED INSIDE THE ROCK.)

FOR CASES WHERE THE DAUGHTER ISN’T GASEOUS, GEOLOGISTS HAVE OTHER WAYS OF ESTIMATING THE ABUNDANCE OF THE DAUGHTER ISOTOPE PRESENT INITIALLY.

REASONS TO BE CONFIDENT ABOUT RESULTS

AGES DETERMINED VIA DIFFERENT RADIOACTIVE MATERIALS AGREE.

AGES OF FOSSILS OF A GIVEN SPECIES AGREE, EVEN IF FOUND IN DIFFERENT LOCATIONS.

AGES ARE CONSISTENT WITH RELATIVE AGES DETERMINED BY ORDERING OF LAYERS IN ROCK.

AGES AGREE WITH THOSE FOUND VIA OTHER MEANS (SUCH AS RELAXATION OF L AMINO ACIDS TO A 50-50 MIX OF L AND D AMINO ACIDS IN DEAD ORGANISMS).

HOW WAS THE EARTH (AND THE REST OF THE SOLAR SYSTEM) FORMED?

COLLISION THEORY – NO LONGER BELIEVED

NEBULAR THEORY – ACCEPTED

ANOTHER STAR PASSES CLOSE TO THE SUN. GAS IS PULLED OFF EACH STAR DUE TO GRAVITATIONAL PULL

OF THE OTHER STAR. GAS FORMS A DISK AND CONDENSE INTO PLANETS.

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *PROBLEMS: COMPUTER MODELS INDICATE THAT THE TEMPERATURE OF THE

GAS IS TOO HIGH FOR IT TO FORM A DISK AND CONDENSE INTO SOLID OBJECTS.

CHANCE OF SUCH A NEAR-COLLISION BETWEEN STARS IS VERY LOW.

• ONLY 100 SUCH EVENTS IN LIFETIME OF UNIVERSE.• WOULD MAKE SOLAR SYSTEM AN ALMOST UNIQUE

STRUCTURE.• WE HAVE DISCOVERED MANY PLANETS ORBITING OTHER

STARS, INCONSISTENT WITH PREDICTIONS OF THIS THEORY.

COLLISION THEORY

CONSERVATION OF ANGULAR MOMENTUM

ANY SPINNING OBJECT HAS ANGULAR MOMENTUM. THE AMOUNT OF ANGULAR MOMENTUM DEPENDS ON

THE OBJECT'S MASS, HOW FAST IT'S SPINNING, AND HOW THE MASS IS DISTRIBUTED WITHIN THE OBJECT.

THE AMOUNT OF ANGULAR MOMENTUM IS CONSERVED, IN OTHER WORDS, IT CAN'T CHANGE (UNLESS SOME EXTERNAL AGENT ACTS ON IT).

WHEN MASS IS PULLED IN CLOSER TO THE AXIS OF ROTATION (THE LINE THE OBJECT SPINS AROUND), IT SPINS FASTER IN ORDER TO KEEP THE AMOUNT OF ANGULAR MOMENTUM FIXED.

EXAMPLE: AN ICE SKATER SPINS FASTER WHEN SHE PULLS HER ARMS IN.

1. 1. Interstellar gas and dust cloud (initially about 1 light year in diameter) starts to collapse gravitationally.

a. Rotation speeds up due to conservation of angular momentum.

b. Cloud flattens into a disk.

c. Temperature increases, more so towards the center.

d. Sun forms in the center.

1. 2. Solar nebula: a rotating disk about 100 AU in diameter

1. 3. Condensation and accretion: dust particles form condensation nuclei and grow due to collisions.

a. At distances less than 2-3 AU out from the sun, only rocky and metallic materials condense.

b. Beyond about 3 AU, it's cold enough for water ice particles to condense.

c. Even farther out, where it's even colder, ammonia and methane ice particles condense.

OUTLINE OF SOLAR SYSTEM FORMATION

•4. Billions of planetesimals are formed. These are rock, metal, and/or ice bodies up to a few kilometers across.

1. 5. The larger planetesimals are massive enough to be pulled togetherby gravity. They collide and coalesce to form protoplanets and protomoons up to a few hundred kilometers across.

1. 6. Gravitational accretion of gas: the largest protoplanets in the cool outer parts of the solar nebula pull in gas, adding to the planet’s mass. In the hotter inner solar nebula, the gravitational pull of the protoplanets isn’t strong enough to hold onto the fast-moving gas molecules. (The molecules are moving faster than the escape velocity from the protoplanet.) Most of the smaller protomoons don’t have enough gravitational pull to hold onto gas molecules, even in the cool outer parts of the nebula.

1. 7. As a result of steps (3) and (6), compositions of planets and moons vary, resulting in:

a. Outer planets that have rocky/metallic cores surrounded by thick gaseous atmospheres.

b. Moons of outer planets that are made of ice and rock, with thin or no atmospheres.

c. Inner planets that are composed of rock and metal, with thin or no atmospheres.

– 8. Cooling off: planets cool off as heat is radiated into space.a. They are hot initially because of the “heat of formation.” (They heat up

during gravitational contraction.)b. Rocky and metallic materials solidify once temperature is low enough.c. Radioactive decay of materials in the interior continues to provide a

source of heat.d. The smaller the planet or moon, the more quickly it cools. The larger

the planet or moon, the more slowly it cools. Therefore, larger planets or moons will remain hot inside for a longer time than smaller planets and moons.

9. Cleaning up: over the course of about 500 million years, the debris left over from the solar system formation is cleared.

a. Some of the remaining planetesimals collide with planets or moons (leaving visible impact craters on anything with a solid surface).

b. The outer planets strongly influence the orbits of many of the remaining icy planetesimals (comets), throwing them into new orbits much farther from the sun (forming the “Oort Cloud”).

c. Inner planets obtain their atmospheric gases and water from outgassing (the escape of trapped gases via volcanic activity) and the impact of cometary material.

d. The gravitational effects of Jupiter (the most massive planet) influence the region of the asteroid belt (between Mars and Jupiter) so that some material remains in stable solar orbit but is unable to coalesce into a larger body.

FORMATION OF THE EARTH FORMED (ALONG WITH THE SUN AND THE REST OF THE

SOLAR SYSTEM) OUT OF A NEBULA 4.6 BILLION YEARS AGO

INITIALLY HOT ENOUGH TO BE MOLTEN

DIFFERENTIATED (SEPARATED INTO LAYERS), THEN COOLED & SOLIDIFIED (MOSTLY)

NO ATMOSPHERE INITIALLY – HOT ENOUGH THAT GAS MOLECULES ARE MOVING FAST ENOUGH TO ESCAPE FROM EARTH'S GRAVITY

ATMOSPHERE AND WATER ADDED LATER VIA OUTGASSING AND COMETARY IMPACTS

DIFFERENTIATION EARTH WAS COMPLETELY MOLTEN FOR THE

FIRST 100 MILLION YEARS DENSER MATERIALS SANK TO THE CENTER RESULT IS A LAYERED STRUCTURE

– CORE: MOSTLY IRON AND NICKEL, INNER PART IS SOLID AND OUTER PART IS MOLTEN

– MANTLE: SEMI-MOLTEN ROCKY MATERIAL (PRIMARILY SILICON AND OXYGEN)

– CRUST: THIN SOLID LOWER-DENSITY ROCKY MATERIAL, CONTINENTAL CRUST IS THICKER (BUT LOWER DENSITY) THAN SEAFLOOR CRUST

PROPAGATION OF SEISMIC (EARTHQUAKE) WAVES ARE USED TO MAP OUT INTERNAL STRUCTURE

PLATE TECTONICS CORE HEATS MANTLE FROM BELOW, CONVECTION

PRODUCES SWIRLY CIRCULATION PATTERNS CONVECTION OCCURS IN A FLUID BECAUSE HOT

FLUID RISES AND COOL FLUID SINKS PLATES FLOAT ON SEMI-LIQUID MANTLE AND MOVE

DUE TO CONVECTION UNDERNEATH – CONTINENTS MOVE WITH TIME– SEAFLOOR SPREADING – PLATES MOVE APART AT

MID-OCEAN RIDGES, MANTLE MATERIAL RISES TO TOP AND COOLS, PRODUCING NEW CRUST

– SUBDUCTION – WHERE PLATES COLLIDE, ONE IS PUSHED UNDER THE OTHER AND ITS MATERIAL IS RECYCLED BACK INTO MANTLE

– MOUNTAIN RANGES CAN BE PRODUCED WHEN PLATES COLLIDE

– EARTHQUAKES PRODUCED WHEN PLATES MOVE

MAGNETIC FIELD ALL MAGNETIC PHENOMENA ARE ULTIMATELY CAUSED

BY MOVING ELECTRIC CHARGES. AN ELECTRIC CURRENT (ELECTRONS FLOWING

THROUGH A MATERIAL) CREATES A MAGNETIC FIELD. AN ELECTRICALLY CONDUCTING MATERIAL (SUCH AS A

METAL) THAT IS MOVING CAUSES A MAGNETIC FIELD (BECAUSE OF THE MOVING CHARGES IN THE MATERIAL).

AS THE EARTH ROTATES, THE MOLTEN IRON IN THE OUTER CORE SWIRLS AND SLOSHES, PRODUCING THE EARTH'S MAGNETIC FIELD.

IF A PLANET HAS A MAGNETIC FIELD, IT MUST HAVE SOME KIND OF ELECTRICALLY CONDUCTING MATERIAL INSIDE OF IT.

FORMATION OF EARTH’S MOON NO OTHER INNER PLANET HAS A LARGE MOON

MOON IS:

– LESS DENSE THAN EARTH, NO IRON CORE

– FEWER VOLATILES (EASILY VAPORIZED MATERIALS)

– COMPOSITION RESEMBLES THAT OF EARTH’S MANTLE

CONDENSATION FROM SOLAR NEBULA NEXT TO EARTH WOULD PRODUCE OBJECT OF SAME COMPOSITION AS EARTH, INCLUDING AN IRON CORE

CURRENT ACCEPTED THEORY – A MARS-SIZE OBJECT COLLIDED WITH EARTH IN THE FIRST 100 MILLION YEARS, MATERIAL THROWN INTO EARTH ORBIT, THEN CONDENSED TO FORM MOON

MOON WAS BOMBARDED BY DEBRIS, FORMING CRATERS AND MARIA (LARGE IMPACT CRATERS FLOODED BY MOLTEN ROCK THAT THEN SOLIDIFIED, LEAVING A SMOOTH FLAT PLAIN)

BOMBARDMENT EARTH (AND OTHER PLANETS AND MOONS)

BOMBARDED BY LEFTOVER PLANETESIMALS IMPACT CRATERS

MANY CRATERS STILL VISIBLE ON EARTH’S MOON AND SOME OTHER INNER PLANETS

ON EARTH, MOST CRATERS WERE EVENTUALLY ERODED AWAY BY WATER AND WIND OR ERASED BY PLATE TECTONICS

IMPACTS OF COMETS AND ASTEROIDS ADDED MOST LIGHT ELEMENTS (HYDROGEN, CARBON, NITROGEN, AND OXYGEN), WATER, AND PERHAPS ORGANIC MOLECULES

ATMOSPHERE AND OCEANS ATMOSPHERE AND OCEANS FORMED VIA:

– BOMBARDMENT BY COMETS AND ASTEROIDS – OUTGASSING (RELEASE OF GAS PREVIOUSLY

TRAPPED INSIDE ROCK) FROM VOLCANOES

EARLY ATMOSPHERE WAS VERY DIFFERENT FROM CURRENT ATMOSPHERE– CONSISTED MOSTLY OF CARBON DIOXIDE (CO2),

CARBON MONOXIDE (CO), NITROGEN (N2), AND WATER VAPOR (H20)

– NO OXYGEN – CURRENT ATMOSPHERE IS MOSTLY NITROGEN

(N2) AND OXYGEN (O2)

RELATIONSHIP BETWEEN TEMPERATURE AND SPEED AND MASS OF AN ATOM OR MOLECULE

RECALL THAT THE HIGHER THE TEMPERATURE, THE FASTER THE ATOMS OR MOLECULES ARE MOVING.

HOWEVER, THE MASS OF AN ATOM OR MOLECULE ALSO AFFECTS HOW FAST IT'S MOVING.

CONSIDER A MIXTURE OF SEVERAL DIFFERENT MOLECULES (SUCH AS THE AIR IN THIS ROOM), ALL AT THE SAME TEMPERATURE:

– LIGHTER MOLECULES MOVE FASTER.

– HEAVIER MOLECULES MOVE MORE SLOWLY.

DEVELOPMENT OF ATMOSPHERE ULTRAVIOLET (UV) RADIATION FROM THE SUN BROKE APART

MANY MOLECULES INTO INDIVIDUAL ATOMS. EXAMPLE: WATER BROKE APART INTO HYDROGEN AND OXYGEN.

HYDROGEN (H AND H2) ESCAPED TO SPACE. (EARTH’S GRAVITY WASN’T STRONG ENOUGH TO HOLD ONTO SUCH LIGHT FAST-MOVING OBJECTS.)

SMALL AMOUNTS OF OXYGEN (O2) AND OZONE (O3) MOLECULES FORMED. OZONE PROTECTS THE SURFACE FROM ULTRAVIOLET RADIATION.

MOST CO2 WAS PULLED OUT OF ATMOSPHERE AND INCORPORATED INTO CARBONATE ROCKS (ACCELERATED BY LIFE, ONCE IT GOT STARTED).

CYANOBACTERIA (EARLY FORM OF LIFE) RELEASED OXYGEN INTO THE ATMOSPHERE.

THE ATMOSPHERE WAS CHANGED DRASTICALLY BY THE PRESENCE OF LIFE!

TODAY’S ATMOSPHERE 78 % NITROGEN (N2) 21 % OXYGEN (O2) 1% ARGON (Ar) 0.01 % CARBON DIOXIDE (CO2)

PLANTS TAKE IN CO2 AND RELEASE O2

ANIMALS TAKE IN O2 AND RELEASE CO2

THE EFFECTS OF ANIMALS VS. PLANTS COMPENSATE FOR EACH OTHER TO KEEP THE AMOUNTS OF O2 AND CO2 ROUGHLY CONSTANT.

LIFE AND THE ATMOSPHERE

LIFE ON EARTH ORIGINATED IN AN ATMOSPHERE CONTAINING LITTLE OR NO OXYGEN.

LIVING THINGS THEN CHANGED THE ATMOSPHERE, ADDING LARGE AMOUNTS OF OXYGEN.

IN AN ATMOSPHERE CONTAINING OXYGEN, COMPLEX ORGANIC MOLECULES CANNOT FORM. OXYGEN INTERACTS WITH THEM AND BREAKS THEM APART.

CLIMATE SUN HAS GOTTEN A LITTLE BRIGHTER OVER

TIME WARMING TILT OF EARTH’S AXIS HAS CHANGED A

LITTLE WITH TIME CHANGES IN SEVERITY OF SEASONS

CO2 CYCLE (DESCRIBED IN TEXT) REGULATES THE EARTH’S CLIMATE, PREVENTS EXTREME CHANGES

VARIATIONS IN GLOBAL CLIMATE HAVE PRODUCED ICE AGES AND “SNOWBALL EARTH” STAGES (EARLY VERY SEVERE ICE AGES)

GREENHOUSE EFFECT HAS CAUSED WARMING

GREENHOUSE EFFECTSUNLIGHT (MOSTLY VISIBLE LIGHT) IS ABSORBED BY A PLANET’S SURFACE.

ENERGY IS RE-RADIATED FROM THE GROUND (WHICH ACTS AS A BLACKBODY), MOSTLY AS INFRARED RADIATION.

INFRARED RADIATION IS ABSORBED BY ATMOSPHERIC “GREENHOUSE GASES”

GREENHOUSE GASES ARE CO2, H2O, CH4, AND OTHERS (MOLECULES WITH 3 OR MORE ATOMS).

GREENHOUSE EFFECT

ATMOSPHERE WARMS UP AS A RESULT OF ABSORBING INFRARED RADIATION FROM THE GROUND.ATMOSPHERE THEREFORE RADIATES (AS A BLACKBODY) MORE RADIATION TO SPACE.EVENTUALLY EQUILIBRIUM IS REACHED SO THAT ENERGY ABSORBED = ENERGY RADIATED, AND TEMPERATURE STABILIZES.FINAL TEMPERATURE IS HOTTER THAN IT WOULD BE WITHOUT ABSORPTION OF INFRARED RADIATION BY ATMOSPHERIC GREENHOUSE GASES.

GREENHOUSE EFFECT

BECAUSE OF THE GREENHOUSE EFFECT, EARTH IS 40K (OR 40OC) HOTTER THAN IT OTHERWISE WOULD BE.

HUMAN INDUSTRIAL ACTIVITY IS ADDING MORE GREENHOUSE GASES TO EARTH’S ATMOSPHERE.

GLOBAL WARMING (AN INCREASE IN AVERAGE PLANET-WIDE TEMPERATURES OVER THE LAST CENTURY OR SO) HAS BEEN MEASURED AND IS REALLY HAPPENING.

THE SCIENTIFIC EVIDENCE IS OVERWHELMING THAT HUMAN ACTIVITY IS RESPONSIBLE FOR GLOBAL WARMING.

CLAIMS TO THE CONTRARY ARE PROBABLY WISHFUL THINKING OR POLITICALLY MOTIVATED.