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C O U R S E 
Our Earth: Its Climate, History, and Processes
David Schultz, University of Manchester
C O U R S E   L E C T U R E 
Measuring Geologic Time
Notes taken on June 19, 2015 by Edward Tanguay
history of the Earth
events in billions of years ago
4.57 Earth's formation (Hadean Eon)
3.8 first evidence of oceans (Archaen Eon)
2.5 oxygen-rich atmosphere (Proterozoic Eon)
0.542 explosion of fossils (Phanerozoic Eon)
0.065 dinosaurs go extinct (Phanerozoic Eon - Cenozoic Era)
0.0002 first hominids
0.000022 maximum extent of last Ice Age
classification scheme for geological time, from largest to smallest
speak in these terms since these dates are rough estimates based on various ways of determining how long ego events occurred
periods or systems
epochs or series
Ma (mega annum)
million years
Ga (giga annum)
billion years
four eons
[1] Hadean Eon - 4570 Ma
named after Hades, or the under world
formation of Earth and Moon
molten earth surface
formation of earliest crust
[2] Archaen Eon - 3800 Ma
oceans formed
single-celled animals
geologic record documents these single-celled fossils their structures they left behind called surmatelites
process of plate tectonics was just beginning
low oxygen concentration in air
[3] Proterozoic Eon - 2500 Ma
increasing oxygen concentration in the atmosphere
periods of glaciations including a period in which the Earth may have been entirely covered in ice
multicellular life began evolving
Ediacaran Period (635-542 Ma)
first multicellular life
first appearance worldwide of somewhat complicated trace fossils
[4] Phanerozoic Eon - 542 Ma
increasing complexity of multicellular life
the colonization of life from the ocean onto the land of plants and animals
the eon in which complex life began to flourish
but also with periodic extinction events that almost ended life on earth
1. Paleozoic Era (542,000,000 - 251,000,000)
Cambrian Period - 542 Ma
rapid diversification of lifeforms known as the Cambrian explosion
produced first representatives of all modern animal phyla
high proportion of lagerstätte sedimentary deposits with exceptional preservation
where "soft" parts of organisms are preserved as well as their more resistant shells
therefore we understand Cambrian biology better than some later periods
Ordovician Period - 485 Ma
life continued to flourish
end of period marked by a significant mass extinction
invertebrates, namely molluscs and arthropods, dominated oceans
fish, the world's first true vertebrates, continued to evolve, first jawed fish
land life had yet to diversify
Silurian Period - 444 Ma
diversification of jawed and bony fish
life also began to appear on land in the form of small, moss-like, vascular plants which grew beside lakes, streams, and coastlines
small terrestrial arthropods (insects, spiders)
but terrestrial life would not greatly diversify and affect the landscape until the Devonian
Devonian Period - 419 Ma
free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents
fish reached substantial diversity during this time, leading the Devonian to often be dubbed the "Age of Fish"
Carboniferous Period - 358 Ma
terrestrial life was well established
amphibians were the dominant land vertebrates
one branch would eventually evolve into reptiles
Permian Period - 298 Ma
the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs
2. Mesozoic Era - 250 Ma
Triassic Period - 250 Ma
began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished
it took into the middle of the period for life to recover its former diversity
the first true mammals
Jurassic Period - 200 Ma
land dominated by dinosaurs
supercontinent Pangaea had begun rifting into two landmasses
created more coastlines and shifted the continental climate from dry to humid
many of the arid deserts of the Triassic were replaced by lush rainforests
first birds and earliest lizards
Cretaceous Period - 145 Ma
oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists
dinosaurs continued to dominate on land
new groups of mammals and birds, as well as flowering plants, appeared
ended with a large mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs and large marine reptiles, died out
3. Cenozoic Era (65,000,000 - today)
Paleogene Period - 65 Ma
Paleocene Epoch - 65 Ma
brackets two major events in Earth's history: (1) the demise of non-avian dinosaurs, giant marine reptiles and much other fauna and flora, and (2) the Paleocene–Eocene Thermal Maximum, a geologically brief interval characterized by extreme changes in climate and carbon cycling
Eocene - 56 Ma
includes the warmest climate in the Cenozoic Era when little or no ice was present on the planet, but ends in an much colder climate
ended in a major extinction event called the Grande Coupure (the "Great Break" in continuity) or the Eocene–Oligocene extinction event
Oligocene - 33 Ma
an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene
Neogene Period - 23 Ma
Miocene - 23 Ma
cooled in a series of ice ages
apes arose and diversified becoming widespread in the Old World
ancestors of humans split away from the ancestors of the chimpanzees
Pliocene - 5.3 Ma
cooled down from the Miocene temperatures
Quaternary Period - 2.5 Ma
Pleistocene - 2.5 Ma
recent period of repeated glaciations
Holocene (11,700 - 1800)
current warm period
(proposed) Anthropocene (1800 - present)
epoch in which humans are affecting the climate
mnemonic for eons and eras of geological time containing life forms on Earth
Proterozoic Eon
(E)VERY - Ediacran Period - 635 Ma - single-celled organisms
Phanerozoic Eon
Paleozoic Era - (FISH) - 542 Ma
(C)AMEL - Cambrian Period - 542 Ma - multicelled diversity explosion
(O)FTEN - Ordovician Period - 485 Ma - diversified ocean life
(S)ITS - Silurian Period - 444 Ma - early jawed and boned fish
(D)OWN - Devonian Period - 419 Ma - the age of fish
(C)AREFULLY - Carboniferous Period - 358 Ma - dominant amphibians
(P)ERHAPS - Permian Period - 298 Ma - mammal ancestral groups
Mesozoic Era - (DINOSAURS) - 250 Ma
(T)HEIR - Triassic Period - 250 Ma - extinction and recovery, therapsids and first mammals
(J)OINTS - Jurassic Period - 200 Ma - age of reptiles, first birds
(C)REAK - Cretaceous Period - 145 Ma - new mammals, ended with dinosaur extinction
Cenozoic Era - (MAMMALS) - 65 Ma
Paleogene Period - 65 Ma
(P)ERHAPS - Paleocene Epoch - 65 Ma - dinosaurs gone, changes in climate
(E)FFECTIVE - Eocene Epoch - 56 Ma - warmest, no ice on planet
(O)ILING - Oligocene Epoch - 33 Ma - transition from tropical to modern ecosystems
Neogene Period - 23 Ma
(M)IGHT - Miocene Epoch - 23 Ma - humans and chimpanzees split
(P)ROLONG - Pliocene Epoch - 5 Ma - climate cooled
Quaternary Period
(P)ERFECT - Pleistocene Epoch - 2 Ma - repeated glaciations, humans evolved into present form
(H)EALTH - Holocene (11,700 - ca. 1800) - current warm period, major human civilizations
(A)GAIN - (proposed) Anthropocene (ca. 1880) - humans altering the climate