L8 | GEOLOGIC TIME SCALE

• GEOLOGIC TIME SCALE

  • Timeline that illustrates Earth’s history based on geologic events and life forms
• GEOLOGIC TIME

  • General reference to long time span that predates human records
• FOSSILS

  • Preserved remains  traces of plant, animals, and other organisms from the past
  • Provides an evidence of the past events in Earth’s geological history
• FOSSIL RECORD

  • History of life is documented by all fossils which preserved in sedimentary rocks
• INDEX FOSSILS

  • Guide or indicator of certain geologic periods
  • Used to correlate the age of the rock strata
  • If 2 different rocks in different areas on the Earth contain the same index fossils, then probably the strata have the same age
• EXTINCTION

  • Termination of a kind of organism or of a group of kinds (taxon), usually a species.
• EON

  • Largest division of geologic time scale 
  • Half a billion years or more
• ERA

  • Second largest division of geologic time scale 
  • Includes two or more periods 
  • Several hundred million years
• PERIOD

  • Third largest division of geologic time scale 
  • Tens of millions of years
• EPOCH

  • Smallest division of geologic time scale
  • Tens of millions of years
• EONS

  • Eonothems
  • Largest division
  • Thousands of millions of years
• 2 MAJOR EONS:

  • Precambrian (Hadean, Archean, Proterozoic)
  • Phanerozoic
• HADEAN EON

  • Hadean  – hades, which means "hell"
• HADEAN EON

  • considered as a chaotic eon mainly due to the meteorites that constantly hit Earth, causing most severe volcanic activities. 
  • the atmosphere and ocean were formed and the core, the crust was also stabilized. 
• ARCHEAN EON

  • characterized by the period of Earth becoming warm, but the atmosphere contains only methane and only few to no oxygen.
  • Lasted for 1.3 Ga (Giga annum). 
  • Most of the Earth is still covered with water.
• ARCHEAN EON

  • Formation of the continents supposed to begin in this eon, but not until the mantel is cooled. O 
  • characterized by having an orange atmosphere mainly due to the abundance of methane.
• PROTEROZOIC EON

  • characterizes when the atmosphere began to have oxygen, eukaryotes spreads, multicellular animals appears, and the continents began to drift away. 
  • Lasted for 1.9 Ga (Giga annum), lasting for a half of the age of the Earth.
• PHANEROZOIC EON

  • current geologic eon in the geologic time scale,
  • abundant animal and plant life has existed. 
  • covers 541 million years to the present.
• ERAS

  • Erathems
• PALEOZOIC ERA

  • Early life
  • in sedimentary layer, fossils of marine invertebrates, which iced near in the shallow rivers were formed
  • Found in preserved rocks are fossils of trilobites and brachiopods
  • Marks the formation of the supercontinent, Pangea.
• MESOZOIC ERA

  • Middle life
  • breakup of the major land masses. 
  • North America began to part from Europe and South America, and Africa began to separate from Australia, New Zealand, and India. 
• MESOZOIC ERA

  • Dinosaurs 
  • The largest creatures that existed during this era which is descendants of the primitive reptiles that survived throughout the Paleozoic era.
• CENOZOIC ERA

  • Periods of ice age played a role of formation of vast geological features on Earth today.
  • Volcanic activities became widespread, forming immeasurable flows of lava and basalt.
• CENOZOIC ERA

  • Warm blooded animals, such as marsupials, and primitive mammals journeyed the land. 
  • Humans begin to left their marks on the land, as scientists observed in the stone tools that were used.
• PERIODS

  • “Systems” 
  • subdivided into eras, eras are subdivided into units of time called periods.
• PALEOZOIC ERA PERIODS

  1. PERMIAN PERIOD
  2. CARBONIFEROUS PERIOD
  3. DEVONIAN PERIOD
  4. SILURIAN PERIOD
  5. ORDOVICIAN PERIOD
  6. CAMBRIAN PERIOD
• PERMIAN PERIOD

  • "age of amphibians"
• CARBONIFEROUS PERIOD

  • subdivided into Pennsylvanian and Mississippian.
• DEVONIAN PERIOD

  • appearances of jawed fish and first amphibians.
• SILURIAN PERIOD

  • first vascular plants appeared.
• CAMBRIAN PERIOD

  • age of trilobites.
• ORDOVICIAN PERIOD

  • diversification of metazoan families took place.
• MESOZOIC ERA PERIODS

  1. TRIASSIC PERIOD
  2. JURASSIC PERIOD
  3. CRETACEOUS PERIOD
• TRIASSIC PERIOD

  • dinosaurs are dominant
• JURASSIC PERIOD

  • birds first appeared in this time.
• CRETACEOUS PERIOD

  • mark of the extinction of dinosaurs.
• CENOZOIC ERA PERIODS

  • PALOEGENE PERIOD
  • NEOGENE PERIOD
  • QUATERNARY PERIOD
• PALEOGENE PERIOD

  • most Earth's climate was tropical. 
  • Continents drifted apart creating vast stretches of oceans.
  • consists of the Paleocene, Eocene, and Oligocene Epoch.
• NEOGENE PERIOD

  • gives rise to early primates. 
  • consists of Miocene and Pliocene Epochs.
• QUATERNARY PERIOD

  • most recent period. 
  • also termed the Anthropogene period.
  • divided into two epochs: Pleistocene and Holocene.