Learning Center
Plans & pricing Sign in
Sign Out

Geologic Time


									Ch. 12
   What makes it difficult to date our Earth and it’s
   Not all rocks can be dated radiometrically.
   WHY NOT?

     To use radiometric dating, all minerals must have been
      formed at the same time. What rocks do NOT fit this
     Sedimentary: Contain particles with isotopes BUT may
      not be the same age as the rock they occur in…(which law
      does this remind you of?)
     Metamorphic: not necessarily when the rock FIRST
     Weathered Rocks
  Explosion                Debris Cools            Death of Star                Planets
  • 13.7 bya               • H and He form         • Supernova                  Created
  • Matter is created      • Clouds of matter      • Creates all           • From
    (protons,                are created and         elements heavier        accumulation of
    neutrons,                condense into           than iron (Fe) in       debris
    electrons)               stars- FUSION           space

Rotation                  Moon Created             Temp. Increases         Outgassing
•Clouds of gas and        •From large collisions   •Earth is HOT!          •From crust releases
 debris rotate and                                 •Iron and Nickel melt    gases
 matter collects in the                             and sinks to core      •Earth cools, water
 center                                                                     vapor condenses,
                                                                            forms clouds, creating
                                                                            rain, and oceans!
   Formation of Earth

   Sun and Early Solar System
   What makes up today’s atmosphere?

   Was it always like this?

   Create a flow chart of HOW Earth’s
    Atmosphere as evolved over time.
                           Rain reduces
             Torrential    water vapor
              rains fill     and CO2
               ocean        dissolves in
               basins      water leaving

               Water       Organisms
               Vapor                         Oxygen is
  Planet                    begin to         added to
             Condenses        use           atmosphere
              forming      photosymt            via
               clouds        hesis         cyanobacteria
   In 4 groups gather information on the history
    of the changing continents and land for:

         Precambrian
         Paleozoic
         Mesozoic
         Cenozoic (p.348-351)

        How has our Earth changed over time?

       Use a 4 column chart on the board to compare
   Define as a class and in your notes: (p.352)
       Stromatolites- dead cyanobacteria + sand grain
       Prokaryotes- mostly simple 1 cell- no nucleus
       Euarkaroytes-develop cells w/ nucleus- well defined
       Cyanobacteria- blue green algae, first to do
        photosynthesis- release O2

       What are the requirements for life? Hospitable
       environment, DNA, RNA, proteins

       From where are amino acids obtained? Amino acids
       from methane and ammonis in early atmosphere
Pre Cambrian:
 makes up 88% of geologic time scale.

 Most rocks DO NOT contain fossils.
       Why not?
   Pre Cambrian rocks are found below the
       Can you think of a location we have discussed where
       you might be able to SEE Pre Cambrian rocks?
   Atmosphere was created
   Cyanobacteria
What do you
   (Can be done as a whole class, partners or
    individually first then share to create class
    model for each ERA p. 354-362)

   Create a concept map for EACH ERA
    (Paleozoic, Mesozoic, Cenozoic)

   Include important information such as animal
    and plant life forms, key life advancements,
    and any other noteable info.
   Choose a GRAPHIC ORGANIZER you feel is
    best for each ERA.

   Sample Graphic Organizers
   While watching the videos, students take down
    3 pieces of important and NEW information
    they learned. (40 minutes)

   Origins of Life

   Share with the class after the video.
   K for Cretaceous T for Tertiary

   Likely due to a large meteorite
     10 km in diameter traveling 90,000 km /hr… WOW
     Struck North America, in Mexico’s Yucatan
     Demise of dinosaurs and many other species

    But it wasn’t SIMPLY due to the impact of the

    Think…how did this affect other aspects that led to the
   Evidence?

       Iridium found in sediment at the time of the KT

       Iridium is rare in the Earth’s crust but abundant in

       Large crater in Mexico’s Yucatan Peninsula
        (Chicxulub Crater)

       “Bulge” on opposite side of Earth!
   A meteorite is a “natural
    object originating in space
    that passes through Earth’s
    atmosphere and falls to the

   Believe it or not, meteorites
    are fairly frequent on Earth.
    The reason we don’t hear
    about them is because they
    land in deserted areas.

   Meteorite in CT?
   Mammals started of small but evolved to the
    some of largest land mammals ever!
   PBS Evolution   BBC Evolution

To top