GEOLOGIC TIMEGEOLOGIC TIME

PRECAMBRIAN TIMEPRECAMBRIAN TIME4.6 B.Y.A. – 600 M.Y.A.

88 PERCENT OF EARTH’S HISTORY

FOSSILS ARE RARE! WHY?

FOSSILS WHERE SOFT BODIED, LACKED BONES, SHELLS, OR OTHER HARD PARTS.

STROMATOLITES

PALEOZOIC ERAPALEOZOIC ERA600 M.Y.A. – 230 M.Y.A.

SUPERCONTINENT PANGEA FORMED

NEW MOUNTAIN RANGES

AGE OF INVERTEBRATES

7 PERIODS (CAMBRIAN, ORDIVICIAN, SILURIAN, DEVONIAN, MISSISSIPPIAN, PENNSYLVANIAN, PERMIAN)

ORGANISMS DURING ERA: TRILOBITES, BRACHIOPODS, FISH, LAND PLANTS, AMPHIBIANS, GIANT COCKROACHES AND DRAGONFLIES.

MADE MOVE TO LAND!

MASS EXTINCTION MARKED END OF ERA

MESOZOIC ERAMESOZOIC ERA230 M.Y.A. – 70 M.Y.A.

PANGEA BROKE UP, FORMING SEPARATE CONTINENTS.

AGE OF REPTILES

LIZARDS, TURTLES, CROCODILES, SNAKES, DINOSAURES, BIRDS.

3 PERIODS (TRIASSIC, JURASSIC, CRETACEOUS)

MASS EXTINCTIONS MARK END OF ERA

CLIMATE: WARM AND MOIST

ANDES, AND ROCKIES FORMED

CENOZOIC ERACENOZOIC ERA70 M.Y.A. – PRESENT

CONTINENTS SIMILAR TO HOW THEY ARE TODAY

ALPS, HIMALAYAS FORMED

ICE AGES

AGE OF MAMMALS! WHY DO YOU THINK MAMMALS BECAME THE DOMINANT ORGANISMS OF EARTH DURING THIS TIME?

2 PERIODS: (TERTIARY, QUATERNARY) ICE AGE SEPERATES THE TWO

7 EPOCHS (Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene)

HOW DO WE KNOW ALL OF THISHOW DO WE KNOW ALL OF THIS

FOSSILS, HALF LIFE, LAW OF SUPERPOSTION

FOSSILSFOSSILS

FOSSILS: THE REMAINS OR TRACES OF ANIMALS OR PLANTS FROM A PREVIOUS GEOLOGIC TIME

PRESERVATION: MUMMIFICATION, AMBER, TAR BEDS, FREEZING

Trace Fossils – tracks, footprints, borings, and burrows

Molds, Casts, and imprints

Caprolites – fossilized poo

Gastroliths – stones in stomach to help grind up food.

WHERE DO YOU LOOK FOR FOSSILS?WHERE DO YOU LOOK FOR FOSSILS?

Places where there is running water Places where weathering is minor

LAW OF SUPERPOSITION (relative dating)LAW OF SUPERPOSITION (relative dating)

PRINCIPLE THAT STATES THAT AN UNDEFORMED SEDIMENTARY ROCK LAYER IS OLDER THAN THE LAYERS ABOVE IT AND YOUNGER THAN THE LAYERS BELOW IT.

Radioactive DatingRadioactive Dating radioactive isotopes ("parents") that spontaneously

decay to form new isotopes ("daughters") while releasing energy. For example, decay of the parent isotope Rb-87 (Rubidium) produces a stable daughter isotope, Sr-87 (Strontium), while releasing a beta particle (an electron from the nucleus). ("87" is the atomic mass number = protons + neutrons.)

http://vcourseware.calstatela.edu/VirtualDating/files/1.0_ClocksInRocks.html

RADIOACTIVE DATING (absolute age)RADIOACTIVE DATING (absolute age)

ELEMENTS IN ROCK EMIT RADIOACTIVE PARTICLES AT A CONSTANT RATE ACTING AS A NATURAL CLOCK

EXAMPLE: CARBON 14 IS A RADIOACTIVE ELEMENT THAT DECAYS AT A RATE OF HALF ITS MASS IN 5,730 YEARS.

IF I HAD 20 GRAMS OF CARBON 14 IN 11, 000 YEARS HOW MUCH WOULD I HAVE?

5 GRAMS!

RADIOACTIVE DATINGRADIOACTIVE DATING

A FOSSIL OF THE OLDEST KNOWN ORGANISM WAS FOUND IN A CAVE – ANALYSIS SHOWED THAT ONLY 1/8 OF THE ORIGINAL POTASSIUM-40 (K40) REMAINED. POTASSIUM-40 HAS A HALF LIFE OF 1.3 BILLION YEARS. HOW OLD IS THE FOSSIL?

The Origin of LifeThe Origin of Life

Video: Origins (Monday)