Excite-Making a Time Scale of Your Year

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Transcript Excite-Making a Time Scale of Your Year

Geologic Time Test
• I can/can do/will know….(see the pink writing on the slides)
– List how old the Earth is
slide 2
– Explain how the start and endings of the divisions on the
Geologic Timeline are determined.
slide 2
– Explain how scientists know all about Earth’s past slide 5
– Define what an index fossil is and how it is a slam dunk in
determining the age of a rock layer.
slide 5
– Place in order, by length, the time spans:
Epoch, Era, Eon, and Period. (longest to shortest)
slide 6
– Explain how an organism's size/complexity tells us about its
position on the Geologic Timeline.
slides 7-12
– List what eon and era we live in
slides 8 &12
– When the dinosaurs disappeared and why
slide 10
– Given fossil evidence, make conclusions about what events
have taken place in history.
slide 11
Geologic Time Scale
• Helps us study Earth’s pastwhich is really old
(estimated 4.6 billion years old)
• Divides Earth’s history into
intervals of time determined by
--major events/changes in the rock layers, and
--the appearance/disappearance of fossils/life
Slow Changes on our Earth
•Mountain forming
Fast Changes on our
• Volcanic
• Earthquake
• Flood
How do we know what has
happened all this time?
• Fossil information
– Tells us what life existed when
• Rock layers/sequencing
– Tells the relative age & what the environment was like
• Index fossils have a wide distribution world-wide, live for a
short period of time in one particular time span, and help date
the layer(s) they are found in.
• Fossilized seashells found in the mountains tells us that there
was no mountains there long ago, just seafloor.
• Fossilized corals on land indicates that a previous ocean
environment existed there.
Divisions & sizes of
Geologic Time spans
• Eon-largest unit of time (Earth’s history has four
• Era- A division of an Eon. The most recent eon is
divided into three eras: Paleozoic, Mesozoic, and
• Periods-Each era is subdivided into a
number of
• Epoch- The periods of the Cenozoic, the most
recent era, are further divided into epochs
“Pre-Cambrian Time”
• Makes up 90% of Earth’s History
• Hadean, Archean, and Proterozoic eons
make up the Pre-Cambrian Time
• Fossil record dominated by tiny, single
celled organisms that can only be seen
with a microscope (bacteria) and soft
bodied animals that didn’t fossilize
(like jellyfish)
• Earth cooled, continents formed
Phaneorozoic Eon
(our current eon)
•Divided into 3 Eras:
•Paleozoic- “ancient life”
•Mesozoic- “middle life”
•Cenozoic- “recent life”
Paleozoic Era
• 542 mya to 251 mya
• All life lived in the ocean at the start. Multi-celled life
• Early Paleozoic =Age of the Invertebrates
• Middle Paleozoic =Age of the Fishes
Vertebrates & insects evolve and first plants
• Late Paleozoic =Age of the Amphibians
Life started to move on land. Reptiles evolve.
Pangaea and mountain ranges form
• Mass extinction happened at the end (248 mya)90% of all species perished.
Mesozoic Era
250 mya to 65 mya
Bigger and more complex life
Age of the Reptiles (dinosaurs dominate)
Pangaea breaks up
Sm. mammals, birds, and flowering plants first
appeared & evolve.
• N. America covered by a sea
• A mass extinction event (asteroid?) 65mya killed
off 50% of all species (& the dinosaurs)
– from the heat at the impact site,
– lack of sunlight and thus photosynthesis world-wide, &
– other catastrophic impact effects (tsunamis, earthquakes, etc)
KT Asteroid
• Is thought to have
caused the mass
extinction of the
dinosaurs as
evidenced by the
lack of fossil size &
diversity afterwards
• Happened 65
million years ago
Cenozoic Era
65 mya to present day (our current era)
Age of Mammals –biggest and most complex life
Ice Age happened during this time
Mammoth, saber-toothed cats and other
large mammals common during the first part
of this time are now extinct
• End of era natural land bridges allowed first
humans and animals to spread around the