Transcript geologic time

GEOLOGIC
TIME III
Fossils, & The Geologic
Time Scale
Let’s Take a Closer Look
• The Geologic Time Scale
• Earth’s age is believed to be 4.6 billion years
• It is broken down into different units and subunits based upon the rocks and fossils within
those rock layers
–
–
–
–
Largest division = EON (ex: Archean, Phanerozoic)
Next largest = ERA (ex: Mesozoic, Cenozoic)
Next largest = PERIOD (ex: Devonian, Jurassic)
Smallest division = EPOCH (ex: Miocene, Pleistocene)
The Time Scale
• Major Units of Time Scale were
first constructed in the 1800s
• Names of these times were
usually given by naming them
after geographic regions where
the rocks from that time were first
studied (ex. Pennsylvanian)
• No absolute dating at that time,
so the whole thing was originally
done using relative dating
• Once radiometric dating was
discovered, the times were put in
place and are continually being
checked and refined
Precambrian – 87% of Earth’s
History
• The Precambrian (eon) is
made up of 3 large eons
totaling over 4 Byrs:
– Hadean – “hell-like”
– Archean – “ancient”
– Proterozoic – “first life”
• Any information from this
time period is sketchy
• Erosion has destroyed most
of the rocks and fossils
• Any fossils that have
survived are rare and
simple in structure
Hadean – Hellfire & Brimstone
• From 4600 – 3800 Mya
• The formation of the
solar system through
planetary bombardment
• Sun was 70% as bright
• Massive volcanism
produces the young
atmosphere probably
made up of CO2, H2O,
CH4, & NH3
• No fossils found this old
Archean – oldest rocks
• From 3800 – 2500 Mya
• Surface of the earth turns
from molten to solid rock
• Oceans form from water
vapor condensation
• Oldest rocks known have
been dated to this eon
• Potentially the first simple
bacteria/algae fossils
• Noxious atmosphere was
very depleted of oxygen
• Continents begin to form
Proterozoic – big changes
• From 2500 – 570 Mya
• Largest Eon (~2 Byrs total)
• Atmosphere enriches with
oxygen due to bacteria—
ozone layer forms too (good)
• Supercontinent Rodinia forms
around 800 Mya
• First multi-cell fossils – simple
– Stromatolites (algae)
• Eukaryotic cell fossils
• Extensive glaciations during
“Snowball Earth”
Phanerozoic – “visible life”
• Three Eras spanning from
570 Mya to present
– Paleozoic – “ancient life”
– Mesozoic – “middle life”
– Cenozoic – “recent life”
• Greatest diversity of land
and ocean organisms
• Fossil record indicates
complex organisms thrive
• Several mass extinctions
• We are still currently living
in the Phanerozoic
Paleozoic – “Cambrian Explosion”
• Spans 570 – 245 Mya
• 7 periods of Paleozoic
– Cambrian, Ordovician,
Silurian, Devonian,
Mississippian,
Pennsylvanian, Permian
• At the beginning of the
Cambrian, the fossil
record goes through an
exponential increase in
diversity and complexity
Burgess Shale (505 mya)
Paleozoic – More specifics
• 3 distinct “ages”
– Age of invertebrates (shells)
– Age of fishes (vertebrates),
– Age of amphibians
• Trilobites, seed ferns, &
amphibians are major index
fossils of the Paleozoic
• Massive swamps resulting in
coal deposits of today
• Supercontinents Laurasia,
Gondwanaland, and
eventually Pangaea form
• Disastrous extinction at the
end of the Permian wiping
out ~90% of all marine &
~70% of all land organisms
Mesozoic – Rise of Dinosaurs
• Mesozoic has 3 Periods
from 245 – 66 Mya
– Triassic
– Jurassic
– Cretaceous
• Pangaea begins to break
apart and form the current
continents
• Warmer climates dominate
• Gymnosperms (nonflowering, naked seed)
appear and become the
dominant plant
Mesozoic – More specifics
• Reptiles rise, dinosaurs
dominate, and shelled eggs
help to protect offspring
– Some reptiles take to the sky
(birds)
– Some reptiles return to the
ocean but keep their air lungs
(gators, turtles, etc...)
• The most famous mass
extinction in the world
occurs at the end of the
cretaceous (K/T boundary)
– Main theory is asteroid
impact changed climate so
drastically that majority of
animals failed to adapt
Cenozoic – Rise of Mammals
• 2 Periods spanning from 66
Mya to present day
– Tertiary
– Quaternary
• 7 Epochs are contained
within the two periods
– Paleocene, Eocene,
Oligocene, Miocene, Pliocene,
Pleistocene, & Holocene
• We are now in the Holocene
• Cenozoic has the fossils of
the organisms which were
able to survive and adapt
after the K/T extinction
Cenozoic – More specifics
• Cenozoic represents less
than 2% of Earth’s history
• Mammals rise and become
the dominant organism on
land
• Angiosperms (flowers)
become the dominant
plant life on land
– This probably helped to
allow the rise of birds and
mammals who both feed on
flowers and plants
• Ice age advances occur
during Pleistocene
– Many organisms go extinct
with ice age climate changes
To Review:
• Fossils are the remains or
traces of preserved,
prehistoric life
• There are several different
ways for fossils to form
• Fossils give us clues about
past environments, past
geology, and paleo-climates
• We can correlate rock layers
over distances using fossils
• The principle of fossil
succession says that fossils
of the rock record succeed
each other in a determinable
& definite order
• The Geologic Time Scale is
divided into subdivisions called
eons, eras, periods, and epochs
• The splits between all of these
time divisions has been
determined by examining both
the rocks themselves and the
fossils within those layers
• The divisions represent spans
during which the geology &
biology have commonalities
• We are currently in the
Phanerozic, the Cenozoic, the
Quaternary and the Holocene
• GMO Rocks
EON
Phanerozoic Eon
ERA
Cenozoic
Mesozoic
Paleozoic
Late Proterozoic
Precambrian Eon
Proterozoic Middle Proterozoic
Millions of Years Ago
(Mya)
66
245
570
900
1600
Early Proterozoic
2500
Late Archean
Archean Middle Archean
Early Archean
Hadean
3000
3400
3800
4600
EON
ERA
PERIOD
Quaternary
Cenozoic
Tertiary
EPOCH
Millions of Years
Ago (Mya)
Holocene
0.01
Pleistocene
1.6
Pliocene
5.3
Miocene
23.7
Oligocene
36.6
Eocene
57.8
Paleocene
66.4
Cretaceous
Mesozoic
Jurassic
Phanerozoic
208
Triassic
245
Permian
286
Pennsylvanian
Carboniferous
Mississippian
Paleozoic
Devonian
Silurian
Ordovician
Cambrian
PRECAMBRIAN
144
TIME...
320
360
408
438
505
570
How will I remember…
Eras
• Precambrian
• Paleozoic
• Mesozoic
• Cenoozoic
• Please Pay My Children
Periods…
•
•
•
•
•
•
•
•
•
•
•
•
Cambrian
Ordivocian
Silurian
Devonian
Mississippian
Pennsylvanian
Permian
Triassic
Jurassic
Cretaceous
Tertiary
Quaternerary
Charlie
Oliver
Still
Drives
My
Purple
Plymouth
To
Jersey
City
Through
Quicksand