Download Geologic Time Scale and Earth Her/History Detailed notes

Geologic Time Scale and Earth Her/History
Detailed notes
Precambrian Eon 4.5 billion – 544 million years ago
Its name means "before Cambrian." All geologic time before the beginning of the Paleozoic era. This
includes about 90% of all geologic time and spans the time from the beginning of the earth.
Hadean Era 4500 to 3800 million years ago
The earliest subdivision of the Precambrian, spanning the time between the formation of the Earth,
about 4.5 billion years ago, and the start of the Archaean era, 3.8 billion years ago. This interval
predates the period of true geologic time since no rocks of this age are known on Earth, with the
exception of a few meteorites. Formation of the solar system and of earth. Earth is in a molten state.
Earth bombarded by planetoids. Formation of the crust. Primal ocean starts to form with organic amino
acids. No life forms in the fossil record.
Archaean Era 3800 to 2500 million years ago
Its name means "ancient." The middle era of Precambrian time, spanning the period between 3.8 and
2.5 billion years ago. There is a permanent crust similar to the structure we see today. Canadian Shield
forms. First signs of erosion as sediment begin to accumulate in the oceans. Life appeared on Earth
during the Archaean, as indicated by the appearance of fossil bacteria (cyannobacteria or blue-green
algae) in rocks thought to be about 3.5 billion years old. Prokaryotes, single-celled micro-organisms
with no distinct organs, are present.
Proterozoic Era 2.5 billion – 544 million
Its name means "early life." The final era of the Precambrian Eon, spanning the time between 2.5
billion and 544 million years ago. Fossils of both primitive single celled (prokaryotes) and more
advanced multi-cellular organisms (Eukaryotes) begin to appear in abundance in rocks from this era.
Sturtian Period 800 million – 650 million
Vendian Period 650 million - 544 million years ago (AKA: Ediacaran)
The latest period of the Proterozoic era, spanning the time between 650 and 544 million years ago.
Sometimes referred to as the Ediacaran period, the Vendian is distinguished by fossils representing a
characteristic collection of complex soft-bodied organisms found at several localities around the world.
Mounds of blue-green algae form structures called stromatolites are considered to be the first fossils.
Photosynthesis creates oxygen in the atmosphere which kills off many of the early living organisms.
Examples of these early life forms are present in water near volcanic vents. Some simple worm-like
fossils. First cnidarians (Greek for “stinging nettle”), which are animals armed with stinging cells
called nematocysts. Precursors to first arthropods (“jointed leg”). Some sponges also present.
Phanerozoic Eon 544 million years ago - present
Means “Revealed Life”. Though it only represents about 10% of earth her/history it is arguably the
most interesting with virtually all life found during this time.
Paleozoic Era 544 million – 248 million
The word Paleozoic is from Greek and means "ancient life." An era of geologic time, from the end of
the Precambrian to the beginning of the Mesozoic, spanning the time between 544 and 248 million
years ago. Fossil record shows first shellfish, insects, plants, fish, spiders, amphibians, and reptiles.
Cambrian Period 544 million – 505 million
It is named after Cambria, the Roman name for Wales, where rocks of this age were first studied. The
earliest period of the Paleozoic era, spanning the time between 544 and 505 million years ago. Major
formation of sedimentary rock. Continents are flooded with shallow seas. Mild climate. “North
America” is tropical. Originally thought to be the first ‘explosion’ of life but has since been adjusted.
Shelled (calcium carbonate) organisms in oceans. Every phylum of invertebrate is represented in fossil
record. Trilobites abundant. First active predators/ hunters. Some brachiopods (“long foot”). Simple
echinoderms (“spiny skin”), which are ancestors of starfish. Possibly some early crinoids or sea lilies.
A few simple jawless vertebrates like lamprey. Early sponges called archaeocyathids present; their
descendants may have been the first reef-builders. Mass extinctions including oldest trilobites.
AKA: “Age of Marine Invertebrates” due to tremendous diversity of organisms.
Ordovician Period 505 million – 440 million
It is named after a Celtic tribe called the Ordovices. The second earliest period of the Paleozoic era,
spanning the time between 505 and 440 million years ago. North America, Europe and Africa colliding
forming first highlands. Seas over North America at their greatest extent. Rocks are mostly
sedimentary. Super-continent called Gondwana in southern hemisphere shifts toward south pole and
much of it was submerged under shallow seas. In the Late Ordovician massive glaciers dropped sea
levels. Mature marine ecosystems develop with some deep-water life. Graptolites- whose fossils look
like saw blades. Fish with notocords (early backbones) present. Jawless fish and other sea life
widespread. Some plant spores have been found suggesting primitive land plants may be in existence.
Mass extinction of 60% of all marine invertebrate genera and 25% of all families become extinct.
Possible reasons for extinction event are the cooling of the ocean and/or oxygen depletion.
Silurian Period 440 million – 417 million
It is named after a Celtic tribe called the Silures. A period of the Paleozoic, spanning the time between
440 and 410 million years ago. Earth continues its mild climate as global temps stabilize. Sea levels
rise to previous levels. Mountains forming in Europe. Most of the world’s salt (halite) deposits occur at
this time. Earliest land plants. Extensive coral reefs present. Jawless fish spread rapidly throughout
fossil record. First fish with jaws as well as the first sharks. Crinoids (sea lilies) abundant. Brachiopods
widespread. Graptolites, conodonts, corals, stromatoporoids and mollusks common. Land being
invaded by arthropods (‘jointed leg”) like relatives of spiders (arachnids) and centipedes. Earliest
vascular plants (plants with xylem and phloem; ferns) found in southern hemisphere; Most common
plants belong to genus Cooksonia; Controversial Baragwanathia (type of advanced vascular plant
called a lycophyte) found in Australia. Modern algae and fungus (ascomycete fossils).
Devonian Period 417 million – 354 million
A period of the Paleozoic era, spanning the time between 410 and 360 million years ago. It is named
after Devonshire, England, where rocks of this age were first studied. Extensive volcanism in the
eastern United States and Canada. Continents are becoming drier. Europe and North America colliding
near equator- orogeny continues. South Pole located in Central Africa as South America, Africa,
Antarctica, India, and Australia dominate southern hemisphere. Fish are dominant life form- armored
fish (ostracoderms), placoderms of huge size, lungfish, Dunklosteous. First lobe-finned fish
(sarcoterygiians) First land animals develop near the end of Devonian; first amphibians. Brachiopods,
echinoderms, corals flourish. Psilotophyta (giant plants) present in southern hemisphere; Archaeopteris
is an example. Also evidence of first seed plants (spermatophytes), which are very modern-type plants.
Oldest known vascular plants found now in northern hemisphere are only one meter tall. Brachiopods
(arm- foot) are at their most diverse. Two major groups of animals colonize land at end of Devonian:
tetrapods (four legged) which are the first vertebrates and closely related to lungfish and amphibians;
and wingless insects and earliest true arachnids. AKA: “Age of Fishes”.
Carboniferous Period 354 million – 290 million
The term ‘Carboniferous’ comes from England and refers to the large coal deposits there.A period of
time in the Paleozoic era that includes the Mississippian (Lower Carboniferus) and the Pennsylvanian
(upper Carboniferous) periods and extended from 354 to 290 million years ago. In the United States the
separation distinguishes between the mostly limestone Mississippian and coal-bearing Pennsylvanian.
The earth’s climate is still warm. Great coal swamps cover much of lowlands on earth. Orogeny in
eastern US (Appalchians), Texas, Colorado, Britain (Hercynian Mountains), Eastern Europe/ Siberia
(Ural Mountains). Laurussia (Europe & North America) collides with Godwanaland (Africa & South
America). Though two massive ice sheets cover the South Pole, there is a decrease in seasonal
variation of temperatures. The milder climates caused the decrease of lycopods (tree-like plants) and
giant insects and the increase of tree ferns. Amphibians reach greatest number and diversity. First
reptiles appear in the late Carboniferous. This is perhaps the greatest ‘innovation’ of this period- an
Amniote egg. This is the design allowed tetrapods to lay eggs away from water- a first in the fossil
record in response to more arid conditions. Earliest amniote fossil was lizard-like Hylonomus. Other
tetrapods include Amphibiamus (type of Temnospondyl), Anthracosaurs, followed by Diapsids (most
reptiles except turtles; dinosaurs and even birds belong to this group), Synapsids (precursors to
mammals, including Dimetrodon) Increase in the diversity of insects; insects are huge. First land snails.
Sharks are abundant. Great forests of ferns, gymnosperms, horsetails. Sphenopsids (like today’s socalled Horse Tails or Equisetum) become more prevalent. Continents are uplifted providing more
terrestrial environments but flooded areas on the continents host bryozoans (“Moss Animals”). Sea
floor dominated by brachiopods, foraminifers (single-celled protests). The Kingdom “Protista” is one
of the four kingdoms including animals, plants, and fungi. Freshwater clams appear. Heavily armored
fish from Devonian extinct. AKA: “Age of Amphibians”
Mississippian Epoch 360 million – 325 million
A period of the Paleozoic era, spanning the time between 360 and 325 million years ago. It is named
after the Mississippi River valley, which contains good exposures of rocks of this age. Coal- forming
swamps.
Pennsylvanian Epoch 325 million – 286 million
A period of the Paleozoic era, spanning the time between 325 and 286 million years ago. It is named
after the state of Pennsylvania where rocks of this age are widespread. Coal- forming swamps at their
fullest extent. All so-called fossil fuels (coal, oil, natural gas) are formed at this time. First reptiles.
Permian Period 286 million – 248 million
The final period of the Paleozoic era, spanning the time between 286 and 248 million years ago. It is
named after the province of Perm, Russia, where rocks of this age were first studied. Extensive
glaciation of southern hemisphere. Appalachians are fully formed- about height of Himalayas. Most of
the shallow seas drain from North America. Reptiles diversify. First coniferous trees; begin to outcompete earlier forests. Many modern insects appear. First Archosaurs (“ruling reptiles”). Finback
reptiles (Dimetridon) are major carnivores. Mass extinction near end of Permian when 80%+ of all life
goes extinct. Last trilobites extinct by 248 million years BP.
Mesozoic Era 248 million – 65 million
The word Mesozoic is from Greek meaning "middle life." An era of geologic time between the
Paleozoic and the Cenozoic, spanning the time between 248 and 65 million years ago. Sometimes
called “Age of Reptiles” but “Age of Dinosaur” more appropriate.
Triassic Period 248 million – 213 million
The earliest period of the Mesozoic era, spanning the time between 248 and 213 million years ago. The
name Triassic refers to the threefold division of rocks of this age in Germany. Volcanism in eastern
US. Overall climate cooler. Many areas are arid (dry) to semi-arid. Pangaea (Supercontinent) is fully
formed. Continents are mountainous. Appalachians broken into basins due to uplift. Fossil record
shows fewer species (decreased diversity) but populations of each are great. Ammonites, clams, snails
in oceans. First dinosaurs as well as the first primitive mammals.
Jurassic Period 213 million – 145 million
The middle period of the Mesozoic era, spanning the time between 213 and 145 million years ago. It is
named after the Jura Mountains between France and Switzerland, where rocks of this age were first
studied. North America and Africa separate. Ocean basins open. Appalachians eroding. Pacific and
North American plates collide with subduction occurring on the western coast. Orogeny from Alaska to
Mexico. Climate warmer than today. Cycads, ginkgo present. Reptiles dominate land, sea, and air.
Archaeopteryx (transition from theropod dinosaur to bird) lives.
Cretaceous Period 145 million – 65 million
The final period of the Mesozoic era, spanning the time between 145 and 65 million years ago. The
name is derived from the Latin word for chalk ("creta") and was first applied to extensive deposits of
this age that form white cliffs along the English Channel between Great Britain and France. Lands are
low and extensive. Rocky Mountains form near end of period. Africa and South America Separate.
Dinosaurs extinct by end of Cretaceous. Marsupials, insectivores abundant and first true flowering
plants appear. Another mass extinction event.
Cenozoic Era 65 million - present
Its name is from Greek and means "new life” or “recent life”. An era of geologic time from the
beginning of the Tertiary period (65 million years ago) to the present.
Tertiary Period 65 million – 1.8 million
The first period of the Cenozoic era (after the Mesozoic era and before the Quaternary period),
spanning the time between 65 and 1.8 million years ago.
Paleocene Epoch 65 million – 55.5 million
It is named after the Greek words "palaois" (old) and "ceno" (new). Earliest epoch of the Tertiary
period, spanning the time between 65 and 55.5 million years ago. Climate is mild to cool. Wide,
shallow continental seas mostly gone. Volcanic activity begins to form Rocky Mountains. Greenland
and North America separate. First known primitive primates and mammalian carnivores. Some modern
plants are present.
Eocene Epoch 55.5 million – 33.7 million
Its name is from the Greek words "eos" (dawn) and "ceno" (new). An epoch of the lower Tertiary
period, spanning the time between 55.5 and 33.7 million years ago. Climate is now mild to tropical.
Many lakes in western North America. Australia separates from Antarctica. India collides with Asia.
Primitive horses, tiny camels, modern birds and gigantic birds present. Hardwoods and redwoods in
western US. Grasslands expand.
Oligocene Epoch 33.7 million – 23.8 million
It is named after the Greek words "oligos" (little, few) and "ceno" (new). An epoch of the early Tertiary
period, spanning the time between 33.7 and 23.8 million years ago. Himalayas and Alps rise from the
subduction of India and Asia. Red Sea forming due to separation of Africa and Arabia. Rockies are
volcanic. California collides with mid-Pacific Ridge. Large browsing mammals. True apes appear.
Origin of many modern families of flowering plants. Species of feline (cats) and canine (wolves)
appear. Early rhinoceros and elephant present in fossil record.
Miocene Epoch 23.8 million – 5.3 million
It is named after the Greek words "meion" (less) and "ceno" (new). A epoch of the upper Tertiary
period, spanning the time between 23.8 and 5.3 million years ago. Climate is moderate. Southern
hemisphere experiences another round of extensive glaciation. Rockies continue to uplift. Volcanic
activity produces the Cascade Mountains. South America and Antarctica separate. Andes Mountains
forming. Whales, apes, and grazing animals widespread. Forests diminish while grasslands continue to
expand. Hyena, bear, seal and raccoon present.
Pliocene Epoch 5.3 million – 1.8 million
It is named after the Greek words "pleion" (more) and "ceno" (new). Final epoch of the Tertiary period,
spanning the time between 5.3 and 1.8 million years ago. Climate cooler. Uplift and mountain-building
continue and many species of animals become extinct. North and south America connect as Panama
uplifts. Large carnivores prowl grasslands. First appearance of upright hominids (Australipithicenes)
Quaternary Period 1.8 million - present
It is named after the Latin word "quatern" (four at a time). The second period of the Cenozoic era,
spanning the time between 1.8 million years ago and the present. It contains two epochs: the
Pleistocene and the Holocene.
Pleistocene Epoch 1.8 million – 8,000
It is named after the Greek words "pleistos" (most) and "ceno" (new). An epoch of the Quaternary
period, spanning the time between 1.8 million years ago and the beginning of the Holocene at 8,000
years ago. Climate fluctuates between mild and cool. Four major glacial advances and retreats (AKA:
Ice Age). Sierra Nevada Mountains uplift. Large numbers of mammal species (giant mammoth,
mastodon, saber tooth cats) begin to disappear by the end of Pleistocene.
Holocene Epoch 8,000 - present
It is named after the Greek words "holos" (entire) and "ceno" (new). An epoch of the Quaternary
period, spanning the time from the end of the Pleistocene (8,000 years ago) to the present. Glaciers
retreat; warming; another interglacial period. Deserts spread on a large scale Planetary spread of
modern humans Homo sapiens (AKA: “Wise Man”). Extinction of many of the large mammals.