Earth History

IT IS ESTIMATED THAT THE EARTH FORMED ALONG WITH THE SOLAR SYSTEM 4 IT IS ESTIMATED THAT THE EARTH FORMED ALONG WITH THE SOLAR SYSTEM 4.6 BILLION YEARS AGO (4,600 MYA) GEOLOGIC TIME SCALE A SUMMARY OF THE MAJOR EVENTS IN EARTH’S HISTORY EON – largest segment of geologic time ERA PERIOD EPOCH – smallest segment of geologic time

READING THE ROCK RECORD RELATIVE TIME VS. ABSOLUTE TIME PLACES EVENTS IN A SEQUENCE BUT DOES NOT IDENTIFY THEIR ACTUAL DATE OF OCCURRENCE IDENTIFIES THE ACTUAL DATES OF GEOLOGIC EVENTS EXAMPLE A LIST IN CHRONOLOGICAL ORDER OF WHAT YOU HAVE DONE TODAY UP UNTIL THIS TIME THE EXACT TIMES AT WHICH YOU DID THESE THINGS

FINDING THE AGE OF ROCKS WITH RELATIVE TIME LAW OF SUPERPOSITION- IN UNDISTURBED SEDIMENTARY ROCKS THE OLDEST ROCK LAYERS ARE AT THE BOTTOM AND THE YOUNGEST ARE AT THE TOP.

LAW OF CROSS-CUTTING RELATIONSHIPS- AN IGNEOUS INTRUSION IS YOUNGER THAN THE ROCK IT HAS INTRUDED INTO.

LAW OF INCLUDED FRAGMENTS - IF FRAGMENTS OF ONE TYPE OF ROCK ARE FOUND IN ANOTHER ROCK LAYER THE ROCK FRAGMENTS MUST BE OLDER THAN THE ROCK LAYER IN WHICH THEY ARE FOUND FAULTED AND FOLDED LAYERS - LAYERS OF ROCK THAT HAVE BEEN FAULTED OR FOLDED MUST HAVE BEEN PRESENT BEFORE THE ACTIONS OF FAULTING OR FOLDING TOOK PLACE FOLDING FAULTING

UNCONFORMITY- A PLACE IN THE ROCK RECORD WHERE LAYERS OF ROCK ARE MISSING BECAUSE OF UPLIFT AND EROSION. THE RESULT CAN BE A LARGE AGE DIFFERENCE BETWEEN THE ROCKS ABOVE AND THOSE BELOW THE EROSIONAL SURFACE (IT APPEARS LIKE A SQUIGGLY LINE IN A CROSS-SECTION)

PLACE THE FOLLOWING EVENTS IN ORDER STARTING WITH THE OLDEST. B I G K M F C A D H J

ROCK CORRELATION MATCHING OF ROCK LAYERS THAT CAN BE SEEN AT THE EARTH’S SURFACE, OVER A LARGE AREA AN OUTCROP IS EXPOSED ROCK LAYERS AT THE EARTH’S SURFACE A KEY BED IS A THIN, WIDESPREAD LAYER, USUALLY OF VOLCANIC ASH, THAT CAN BE USED TO CORRELATE AN EXACT POINT OF TIME

FOSSILS A FOSSIL IS ANY EVIDENCE OF EARLIER LIFE PRESERVED IN THE ROCK ORIGINAL REMAINS (RARE) – THE ACTUAL UNCHANGED REMAINS OF THE PLANT OR ANIMAL ARE PRESERVED. REPLACED REMAINS – THE SOFT PARTS OF THE ORIGINAL ANIMAL HAVE DISAPPEARED AND THE HARD PARTS HAVE BEEN REPLACED BY MINERAL MATERIAL. (PETRIFIED WOOD)

MOLDS AND CASTS – FOSSIL SHELLS OR BONES ARE DISSOLVED COMPLETELY OUT OF THE ROCK LEAVING A HOLLOW DEPRESSION IN THE ROCK. NEW MINERAL MATERIAL FILLS THE MOLD IT FORMS A CAST OF THE ORIGINAL FOSSIL. TRACE FOSSILS – EVIDENCE OF LIFE OTHER THEN REMAINS, WHICH INCLUDES ANY IMPRESSIONS LEFT IN THE ROCK. (TRAILS, FOOTPRINTS, TRACKS, BURROWS)

INDEX FOSSIL EASILY IDENTIFIABLE SHORT-LIVED WIDESPREAD OCCURRENCE

MEASURING ABSOLUTE TIME TREE RINGS EACH RING REPRESENTS A SINGLE YEAR (SPRING/FALL) THE WIDTH OF THE RING DEPENDS UPON THE TEMPERATURE AND RAINFALL VARVES GLACIAL LAKE DEPOSITS. A THICK LIGHT COLORED LAYER IN THE SUMMER AND A THIN DARK LAYER IN THE WINTER

RADIOACTIVE DATING USED TO DATE FAR BACK IN TIME. CERTAIN ROCKS CONTAIN RADIOACTIVE ISOTOPES RADIOACTIVE ISOTOPES ARE ATOMS OF ELEMENTS THAT GIVE OFF RADIATION FROM THEIR NUCLEI RADIOACTIVE DECAY IS THE PROCESS BY WHICH A RADIOACTIVE ISOTOPE CHANGES INTO A NEW STABLE ELEMENT

HALF-LIFE THE RATE AT WHICH A RADIOACTIVE ELEMENT DECAYS. IT IS THE TIME IT TAKES FOR HALF OF THE ATOMS OF THE RADIOACTIVE ELEMENT TO DECAY TO A STABLE END PRODUCT (SEE PAGE 1 OF THE ESRT) AT THE END OF EACH HALF-LIFE, HALF OF THE RADIOACTIVE MATERIAL REMAINS PARENT ISOTOPE = THE RADIOACTIVE ISOTOPE THAT BEGINS DAUGHTER ISOTOPE = THE STABLE ISOTOPE THAT HAS BEEN CHANGED

RADIOCARBON DATING USES THE RADIOACTIVE ISOTOPE CARBON-14 FOUND IN ALL LIVING THINGS. BECAUSE CARBON-14 IS CONTINUALLY ABSORBED BY FOOD AND WATER IT STAYS CONSTANT IN LIVING THINGS. WHEN THE LIVING THING DIES THE PERCENTAGE OF CARBON-14 DECREASES AT THE RATE OF ITS HALF-LIFE. CAN BE USED TO DATE BACK ABOUT 100,000 YEARS

URANIUM LEAD METHOD IS USEFUL TO DATE ROCKS OLDER THAN 10 MILLION YEARS. CAN BE USED ONLY ON IGNEOUS ROCKS THAT CONTAIN THE RIGHT KIND OF URANIUM RUBIDIUM-STRONTIUM METHOD CAN ALSO BE USED TO DATE OLDER ROCKS BECAUSE OF ITS LONG HALF-LIFE. IT IS ALSO VERY COMMONLY FOUND IN IGNEOUS ROCKS. POTASSIUM-ARGON METHOD IS VERY USEFUL SINCE POTASSIUM-40 CAN BE FOUND IN METAMORPHIC, SEDIMENTARY, AND IGNEOUS ROCKS. IT CAN DATE OLDER ROCKS BUT MAY ALSO DATE ROCKS AS YOUNG AS 50,000 YEARS

Divisions of Geologic Time Eras are subdivided into periods...periods are subdivided into epochs. Era Period Epoch E + P = EP

Divisions of Geologic Time Geological time begins with Precambrian Time. Precambrian time covers approximately 88% of Earth’s history.

FOUR Eras… PRE-CAMBRIAN – 88% of earth’s history Paleozoic (ancient life) 544 million years ago…lasted 300 million yrs Mesozoic (middle life) 245 million years ago…lasted 180 million yrs Cenozoic (recent life) 65 million years ago…continues through present day

Paleozoic Era (Ancient Life) The Cambrian period is the 1st period of the Paleozoic Era. “Age of the Trilobites” Explosion of life in the oceans began during this era. Most of the continents were covered in warm, shallow seas. Invertebrates were dominate - Trilobites Fish emerged during this time Fish led to the arrival of amphibians The end of the Paleozoic era is called the “Age of Amphibians” Early land plants including mosses, ferns and cone-bearing plants. The early coal forming forests were also formed during this time.

Paleozoic Era Much of the limestone quarried for building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during the Paleozoic. The Cambrian (beginning) opened with the breakup of the world-continent Rodinia and closed with the formation of Pangaea, as the Earth's continents came together once again. This event is thought to have caused the climate changes that led to mass extinction event. The Appalachian mountains were formed during this time.

Paleozoic Era At the end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species and 70% of land animals. Possible causes of this Mass Extinction Event Lowering of sea levels when the continents were rejoined as Pangaea (convergent boundary) Increased volcanic activity (ash and dust) Climate changes – cooler climate

Trilobites Lived in Earth’s ancient seas Extinct before the dinosaurs came into existence Cambrian Period is know as the “Age of the Trilobites” (put in on table)

Brachiopods Marine animals that resemble clams.

Early Fish Early fish did not have jaws. Some species of sharks were in existence at this time.

Frilled Shark that was found in Japan in January 2007 Frilled Shark that was found in Japan in January 2007. This shark was considered a “living fossil”

Early Land Plants Mosses Cone bearing plants Ferns

Mesozoic Era – Middle Life At the beginning of this era the continents were joined as Pangaea. Pangaea broke up around the middle of this era. Reptiles became the most abundant animals because of their ability to adapt to the drier climate of the Mesozoic Era. Skin maintains body fluids Embryos live in shells

Mesozoic Era Dinosaurs were also very active in this era. First small dinosaurs appeared in the Triassic Period. Larger and more abundant dinosaurs appeared in the Jurassic Period. Small mammals and birds also appeared during this era. The mammals were small, warm-blooded animals. Hair covering their bodies. These characteristics help them survive in changing environments.

Mesozoic Era The main plant life of this time were Gymnosperms or plants that produce seeds, but no flowers. Pine Trees Flowering plants appeared during the END of this era.

Mesozoic Era This era ended with a mass extinction event about 65 million years ago. Many groups of animals, including the dinosaurs disappeared suddenly at this time. Many scientists believe that this event was caused by a comet or asteroid colliding with the Earth.

Crater sites on Earth

Mesozoic Era – Mass Extinction Event Asteroid or Comet collides with Earth. Huge cloud of smoke and dust fills the air Blocks out sunlight Plants die Animals that eat plants die Animals that eat plant-eaters die. However, not all forms of life died during this event. Many animals that you see today are descendants from the survivors of this extinction event.

Mesozoic Reptiles

Mesozoic Mammals

Mesozoic Plants Flowering plants evolved towards the end of the Mesozoic Era.

Cenozoic Era – Recent Life Began about 65 million years ago and continues today!!!!! Climate was warm and mild. Marine animals such as whales and dolphins evolved. Mammals began to increase and evolve adaptations that allowed them to live in many different environments – land, air and the sea. Grasses increased and provided a food source for grazing animals Many mountain ranges formed during the Cenozoic Era Alps in Europe and Himalayas in India; Rocky Mountains in the USA

Cenozoic Era Growth of these mountains may have helped to cool down the climate Ice Ages occurred late in the Cenozoic Era (Quaternary Period). As the climate changed, the animals had to adapt to the rise and fall of the oceans caused by melting glaciers. This era is sometimes called the “Age of Mammals”

Cenozoic Era Marine animal examples: Land animal examples: Algae, Mollusks, Fish and Mammals Land animal examples: Bats, Cats, Dogs, Cattle and Humans Humans are thought to have appeared around 3.5 million years ago (during the most recent period – Quaternary). Flowering plants were now the most common plant life.

Cenozoic Mammals

Flowering Plants were common during the Cenozoic Era