Geologic time

• The geological timescale is divided into eons, eras, periods, epochs, ages.
• Period - even smaller divisions within an era
• Epoch - the smallest division on the geological timescale
• Geologists use relative age dating to determine the sequence of events in Earth's history
• Relative Dating Methods include Stratigraphy (rock layer), Superposition (older at bottom), Cross-cutting Relationships (younger intrusions cut through older rocks)
• HOW OLD IS EARTH? 4.543 BILLION YEARS
• JAMES HUTTON One of the first scientists to understand geologic time The landscapes like mountains and oceans formed over long period of time through gradual processes. FATHER OF GEOLOGY
• GEOLOGIC TIME SCALE It is a system of chronological measurement that relates rock layers to time.
• 1. EON - largest unit of time for the geologic time scale 2) ERA - subsections of longer eons and consist of groups of shorter periods - era names typically end in the suffix “-ozoic”
• 3) PERIOD - subsections of longer eras and consist of groups of shorter epoch - period names have a range of ending but the most common suffixes are "-an", "-ic", and "-ous". 4) EPOCH - an event or a time marked by an event that begins a new period or development
• GEOLOGIC TIME SCALE TIME EON 0.5 BILLION YEARS OR MORE ERA SEVERAL HUNDRED MILLION YEARS PERIOD TENS TO SEVERAL HUNDRED MILLION YEARS EPOCH TENS OF MILLION OF YEARS
• WE HAVE FOUR ERA PRE CAMBRIAN PALEOZOIC MESOZOIC CENOZOIC
• PRE CAMBRIAN - about 5 bya to 600 mya - BEFORE CAMBRIAN
• PRE-CAMBRIAN PROTEROZOIC PERIOD 5 BILLION YEARS AGO Algae, sponges, fungi
• PALEOZOIC - means “AGE OF THE ANCIENT LIFE” - an era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic - the word PALEOZOIC is from GREEK and means “OLD LIFE”
• Permian Period (360 million years ago):

  • Amphibians are dominant
  • Insects and non-vascular plants present
  • Extinction of trilobites
  • First reptiles appear
• Carboniferous Period:

  • Age of forests
  • Emergence of first reptiles
• Devonian Period (400 million years ago):

  • Fishes are dominant
  • Emergence of first land plants
  • First amphibians appear
• Silurian Period (430 million years ago):

  • Fish, first arthropods, mollusks, and invertebrates present
  • Age of invertebrates
• Ordovician Period (435 million years ago):

  • Corals present
  • Age of invertebrates
• Cambrian Period (600 million years ago):

  • Trilobites present
  • Age of amphibians
• MESOZOIC - means “AGE OF THE MEDIEVAL LIFE” - an era of geologic time between Paleozoic and the Cenozoic - the word MESOZOIC is from GREEK and means “MIDDLE LIFE”
• MESOZOIC CRETACEOUS PERIOD 130 MILLION YEAR AGO EXTINCTION OF DINOSAURS JURASSIC PERIOD 180 MILLION YEARS AGO FIRST FLOWERING PLANTS, FIRST BIRDS TRIASSIC PERIOD 230 MILLION YEARS AGO DINOSAURS ARE DOMINANT, FIRST MAMMALS OCCURED AGE OF REPTILES - CRETACEOUS PERIOD - JURASSIC PERIOD - TRIASSIC PERIOD
• CENOZOIC - means “AGE OF RECENT LIFE” - an era of geologic time from the beginning of the Tertiary period to the present - the word CENOZOIC is from Greek and means “NEW LIFE”
• CENOZOIC QUATERNARY PERIOD 1 MILLION YEAR AGO DOMINANCE OF HUMANS TERTIARY PERIOD 65 MILLION YEARS AGO HERBS AND GRASSES, MODERN MAMMALS AND BIRDS AGE OF MAMMALS - TERTIARY PERIOD AGE OF HUMANS - QUATERNARY PERIOD
• sedimentary rocks form when sediments accumulate and harden into solid rock.
• the three types of rocks are sedimentary, metamorphic, and igneous.