Geologic science/Geologic Time... Geologic Time ¢â‚¬¢ The first geologic...

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Transcript of Geologic science/Geologic Time... Geologic Time ¢â‚¬¢ The first geologic...

  • Geologic Time

  • Geologic Time

    • The first geologic time scale was proposed in 1913 by the British geologist Arthur Holmes (1890 - 1965). This was soon after the discovery of radioactivity, and using it, Holmes estimated that the Earth was about 4 billion years old - this was much greater than previously believed.

  • The Divisions of Precambrian


  • Precambrian Era • 4.6 billion years ago, the Earth was born.

    • Nearly 4 billion years passed after the Earth's inception before the first animals. This stretch of time is called the Precambrian.

    • It makes up roughly seven-eighths of the Earth's history

    • During the Precambrian, the most important events in biological history took place.

  • Precambrian Era

    • The Earth formed, life arose, the first

    tectonic plates arose and began to

    move, eukaryotic cells evolved, the

    atmosphere became enriched in

    oxygen -- and just before the end of

    the Precambrian, complex multi-

    cellular organisms, including the first

    animals, evolved.

  • Precambrian Earth

  • Precambrian Era

    • Also divided into different Eons:

    –Hadean – Earths creation

    –Archean – Earliest Rocks form

    –Proterzoic - First organisms with

    well-developed cells form.

  • Paleozoic Era Divisions

  • Paleozoic – “Ancient Life”

  • The Paleozoic Era

    • At its beginning, multi-celled animals underwent a dramatic explosion in diversity, and almost all living animal phyla appeared within a few millions of years.

    • At the other end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species. The causes of both these events are still not fully understood

  • Paleozoic Era

    • The Paleozoic took up over 300 million years.

    • During the Paleozoic there were six major continental land masses.

    • These Paleozoic continents experienced tremendous mountain building along their margins, and numerous incursions and retreats of shallow seas across their interiors.

  • Gondwana and the Continental

    Landmasses During Paleozoic Period

  • Cambrian Period

    • "Age of Trilobytes" -The Cambrian

    Explosion of life occurs; all existent phyla

    develop. Many marine invertebrates

    • First vertebrates. Earliest primitive fish.

    Mild climate.

    • Mass Extinction of trilobites and nautiloids

    at end of Cambrian (50% of all animal

    families became extinct), probably due to


  • The Cambrian Sea

  • Ordovician Period

  • Ordovician Period

    • First corals.

    • Primitive fishes, seaweed and fungi.

    Graptolites, bryozoans, gastropods,

    bivalves, and echinoids.

    • High sea levels at first, global cooling and

    glaciation, and much volcanism.

    • North America under shallow seas. Ends

    in huge extinction, due to glaciation.

  • Silurian Period

  • Silurian Period

    • Primitive plants appear on land.

    • The first jawed fishes

    • First vascular plants (plants with water-

    conducting tissue) appear on land

    • High seas worldwide. Brachiopods,

    crinoids, corals.

    • First insects appeared.

  • Devonian Period – Age of Fishes


  • Devonian Period

    "The Age of Fishes"

    • Fish and land plants become abundant and diverse.

    • First amphibians appear (evolved from the lungfish). First sharks, and bony fish.

    • Many coral reefs, brachiopods, crinoids.

    • New insects appeared.

    • Mass Extinction (345 mya) wiped out 30% of all animal families) probably due to glaciation or meteorite impact

  • Carboniferous Period

  • Carboniferous Period

    (Mississippian & Pennsylvanian)

    • Wide-spread coal swamps and many


    • Appalachian Mountains form.

    • Amphibians become more common.

    • First true reptiles.

    • The first cockroaches appear

    • First winged insects

  • Model of a Pennsylvanian

    Coal Swamp

  • Mountains formed during this


  • Amphibians of the Permian Period

  • Permian Period

    "The Age of Amphibians"

    • Amphibians and reptiles dominant.

    • Gymnosperms dominant plant life.

    • The continents merge into a single super- continent, Pangea.

    • Phytoplankton and plants oxygenate the Earth's atmosphere to close to modern levels.

    • The Permian ended with largest mass extinction. Trilobites go extinct, as do 50% of all animal families, 95% of all marine species, and many trees, perhaps caused by glaciation or volcanism

  • Late Paleozoic Plate Movements

  • Mesozoic Era

    245 – 208 MYA

  • Mesozoic Era

    • The Mesozoic is divided into three time periods:

    – the Triassic (245-208 Million Years Ago),

    – the Jurassic (208-146 Million Years Ago),

    – and the Cretaceous (146-65 Million Years Ago).

    • Mesozoic means "middle animals", and is the time during which the world fauna changed drastically from that which had been seen in the Paleozoic.

  • Mesozoic Era • Dinosarus, evolved in the Triassic, but were not

    very diverse until the Jurassic.

    • Except for birds, dinosaurs became extinct at the

    end of the Cretaceous.

    • The Mesozoic was also a time of great change

    in the terrestrial vegetation. The early Mesozoic

    was dominated by ferns, cycads

    • Modern gymnosperms, such as conifers, first


    • By the middle of the Cretaceous, the earliest

    angiosperms had appeared

  • Mesozoic Plant Life

  • Dinosaurs of the Triassic Period

  • Triassic Period

    • The first dinosaurs, mammals, and crocodiles appear.

    • Mollusks are the dominant invertebrate.

    • Many reptiles, for example, turtles.

    • True flies appear.

    • Triassic period ends with a minor extinction 213 mya (35% of all animal families die out, including marine reptiles). This allowed the dinosaurs to expand

  • Jurassic Period

  • Jurassic Period

    • Many dinosaurs, including the giants.

    • The first birds appear (Archaeopteryx).

    • The first flowering plants evolve.

    • Many ferns, cycads, gingkos, rushes,


    • Flying reptiles, pterosaurs.

    • Minor extinctions at 190 and 160 mya.

  • Earth During the Jurassic Period

  • Life of the Cretaceous Period

  • Cretaceous Period

    • The heyday of the dinosaurs.

    • The earliest-known butterflies appear as well as

    the earliest-known snakes, ants, and bees.

    • High tectonic and volcanic activity.

    • Primitive marsupials develop.

    • Continents have a modern-day look.

    • Ended with large extinction (the K-T extinction)

    of dinosaurs, pterosaurs, ammonites, about 50

    percent of marine invertebrate species, etc.,

    probably caused by asteroid impact or volcanism.

  • What happened to the dinosaurs?




  • Cenozoic Era

    65 MYA to Present

  • Cenozoic Era the Age of Mammals

  • Cenozoic Era

    • The Cenozoic is the most recent of the

    three major subdivisions of animal history.

    • The Cenozoic is called the Age of

    Mammals, because the largest land

    animals have been mammals during that


    • The Cenozoic is divided into two main

    sub-divisions: the Tertiary and the


  • Tertiary Mammals

  • Tertiary Period

    • First large mammals and primitive


    • Mammals abound. Rodents appear.

    Mammals return to the sea.

    • Flower plants thrive.

    • More mammals, including the horses,

    dogs and bears. Modern birds.

    • First hominids (australopithecines).

    • Continental glaciers repeatedly cover NA

  • Quaternary Period

    • The first humans (Homo Sapiens) evolve.

    Mammoths, mastodons, saber-tooth

    tigers, giant ground sloths.

    • A mass extinction of large mammals and

    many birds happened about 10,000 years

    ago, probably caused by the end of the

    last ice age.

    • Human ci