Q1 L2 - Earth: History and Geologic Time

• petrology


  It is the branch of geology that deals with the origin, composition, structure, and classification of rocks.
• stratigraphy


  studies rock layers (strata) and layering (stratification).
• paleontology


  study of life that existed prior to, or sometimes at the start of, the Holocene epoch.
• relative dating


  places events or rocks in their chronological sequence without knowing their actual age.
• this is based on the information gathered from study of rock's composition and structure, rock layers, and fossils

  geologic timescale
• this represents the interval of time occupied by the geological history of earth

  geologic timescale
• this provides a meaningful time frame within which events of the geologic past are arranged

  geologic timescale
• this dating method places events or rocks in their chronological sequence in order of occurrence without actually knowing the actual age

  relative dating
• the very top of the rock layer indicates that it's younger or older?


  younger
• the very bottom of the rock indicates that it's younger or older?


  older
• this dating method cannot tell exactly how many years have passed since the event happened

  relative dating
• what are the four basic principles of relative dating?

  original horizontality, superposition, cross-cutting relationship, inclusions
• this principle says that sedimentary rocks are deposited as horizontal/nearly horizontal layers. any deviation indicates deformation

  principle of original horizontality
• this principle says that the layer at the bottom is the oldest, successively higher levels are successively higher

  principle of superposition
• this principle says geologic features like faults or igneous intrusions are younger than the rocks they cut across

  principle of cross-cutting relationship
• what are the two types of dating methods

  relative dating, absolute dating
• this principle says if rock fragments are in a rock layer, rock fragment inside is older

  principles of inclusions
• this dating method determines the actual age of rock events

  absolute dating
• this dating method looks at the decay rate of certain radioactive isotopes within fossils, rocks, and artifacts

  absolute dating
• geologists make use of information derived from this object to define and identify subdivisions of geologic timescale

  fossils
• this is a remnant or trace of organisms of a past geologic age

  fossils
• what are the 4 classifications of fossils based on their information

  true form fossils, mold fossils, cast fossils, trace fossils/ichnofossils
• this is a type of fossil wherein the entire animal or plant is trapped and preserved in ice, tar, etc like mammoths discovered in siberia and alaska

  true form fossils
• this is a type of fossil wherein it is a hollow impression of living thing in a rock and only reflects the shape and surface marking of the organism

  mold fossils
• this is a type of fossil that is created when mold fossils get filled with mineral and it forms a replica of the original fossil

  cast fossils
• this is another name of trace fossils


  ichnofossils
• this is a type of fossil that is an impression on rocks that shows various activity. it can be a footprint, egg droppings, or even nests of animals

  trace fossils
• this is a technique that knows fossil organisms succeed one another in a definite and determinable order and therefore, any time period can be recognized by its fossil content

  fossil succession
• these are fossils that are recognized as time indicators and are associated with a particular span of geologic time. they are used in correlating rocks of similar age in different regions

  index fossils
• enumerate the 2 periods of the geologic time scale

  precambrian, phanerozoic
• enumerate the 3 eons in precambrian period


  hadean, archaean, proterozoic
• enumerate the three phanerozoic eras


  paleozoic, mesozoic, cenozoic
• lasted for 800ma, from 4.6-3.8 gya

  hadean
• this was considered "chaotic eon" and its name means "hell"


  hadean
• earth surface continually bombarded by meteorites, very hot mantle caused severe volcanism


  hadean
• the oceans and atmosphere in this eon formed and core and crust were stabilized


  hadean
• 3.8-2.5 gya, lasted for 1.5gya

  archaean eon
• earth was prob warm; atmosphere mostly contained methane no oxygen; caused the sky to be ORANGE; most covered with ocean; sea is GREEN because of iron; shoreline littered with stromatolites

  archaean eon
• continent formation began during this eon

  mesozoic era
• 2.5gya-542mya, lasted for 1.9 gya; longest eon

  proterozoic eon