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Science Unit 2 Earth's History

Terms in this set (76)

the law of uniformitarianism
a principle that states that geologic processes that happened in the past can be explained by current geologic processes
fossils
the traces or remains of an organism that lived long ago, most commonly preserved in sedimentary rock
trace fossil
a fossilized structure that formed in sedimentary rock by animal activity on or in soft sediment
tracks
footprints made by animals in soft sediment that later become hard rock
coprolites
animal dung
burrows
Pathways or shelters made by animals
petrification
the process through which an organisms tissues are replaced by minerals
climate
the weather conditions in the area over a long period of time
ice core
a long cylinder of ice
fossil record
all of the fossils that have been discovered on Earth
composition
the ______________ of sedimentary rock shows the source of the sediment that makes up the rock
texture
The _____________ of sedimentary rock shows the environment in which the sediment was carried and deposited
the five ways fossils can form
being trapped in amber, being trapped in asphalt, being buried in rock, becoming frozen, and becoming petrified
fossils
___________ tell scientists how life forms have changed over time
fossils
_____________ tell scientists about environmental changes over time
fossils
___________ can be used to determine relative ages of rocks
ripple marks
______________ record the motion of the wind or water waves over sediment
mud cracks
_____________ form when fine grained sediments at the bottom of a shallow body of water are exposed to the air and dry out
surface features
Earth's _________________ tell us how continents move and how landforms change over time
Pangaea
The name of the single landmass that broke apart 200 million years ago
weathering and erosion
_____________________ change landforms over time and we can use fossils to tell what they looked like near the landform
sedimentary rocks
To find the relative ages of rocks, scientists study the layers in ___________________________
tilting
________ happens when Earth's forces move rock layers up or down unevenly
folding
the bending of rocks that can happen when rock layers are squeezed together
relative dating
Determining whether an object or event is older or younger than other objects or events
the law of superposition
a principle that states that younger rocks lie above older rocks if the layers have not been disturbed
fault
a break or crack in Earth's crust where rocks can move
intrusion
igneous rock that forms when magma is injected into rock and then cools and becomes hard
unconformity
a break in the geologic record that is made when rock layers are eroded or when sediment is not deposited for a long period of time
the law of crosscutting relationships
the law that states that a fault or a body of rock, such as an intrusion, must be younger than any feature or layer of rock that the fault or rock body cuts through
geologic column
an ordered arrangement of rock layers that is based on the relative ages of the rocks, with the oldest rocks at the bottom
geologic column
A ______________________ can be used to compare relative ages of rocks
absolute dating
determining the actual age of an event or object in years
isotopes
Atoms of the same element that have a different number of neutrons
radioactive
unstable isotopes are called ______________ isotopes
radioactive decay
The breakdown of a radioactive isotope into a stable isotope of the same element or of another element.
parent isotope
a radioactive isotope
daughter isotope
the stable isotope produced by the radioactive decay of the parent isotope
half-life
the time needed for half of a sample of a radioactive substance to undergo radioactive decay to form daughter isotopes
radiometric dating
finding the absolute age of a sample by determining the relative percentages of a radioactive parent isotope and a stable daughter isotope
igneous rock
the best rock for radiometric dating
radiocarbon dating
The age of wood, bones, shells, and other organic remains can be found by using ____________________________
potassium-argon dating
used to date igneous volcanic rocks that are between about 100,000 years and a few billion years old
uranium-lead dating
used to determine the age of igneous rocks that are between 100 million years and billions of years old
lead
daughter isotope of uranium
argon
daughter isotope of potassium
uranium-lead dating
________________was used to find the earliest accurate age of Earth
meteorites
small, rocky bodies that have traveled through space and fallen to Earth's surface
index fossils
fossils that are used to estimate the absolute age of the rock layers in which they are found
tropites
lived between 230 and 208 million years ago
trilobites
closest living relatives are horseshoe crabs, spiders, and scorpions
Phacops rana
a trilobite that lived between 405 million and 306 million years ago
4.6 billion years old
the age of Earth
geology
the scientific study of the origin, history, and structure of Earth and the processes that shape it
the law of catastrophism
the principle that states that all geologic changes occur suddenly
catastrophes
unpredictable, large scale, sudden events
geologic time scale
the standard method used to divide Earth's long natural history into manageable parts
eons
the largest unit of geologic time
Precambrian Time
the Hadean, Archean, and Proterozoic eons together
eras
smaller units of time that eons may be divided into
periods
units of time that an era is subdivided into
epochs
the periods of the Cenozoic era are further divided into ________________
Earth's features
____________ formed during sudden events called catastrophes
James Hutton
a Scottish farmer and scientist that studied rock formation in Scotland
Cenozoic
We live in the ___________ Era
Hadean, Archean, Proterozoic, Phanerozoic
the four eons
five
at least ____ divisions of geologic time have ended in large mass extinction events
Paleozoic
The ___________ era ended about 250 million years ago with the largest extinction event known. More than 90 percent of marine species and 70 percent of land species are thought to have become extinct
Mesozoic
The _______________ era ended with the extinction of dinosaurs and many other organisms about 65 million years ago
oxygen
The atmosphere had no free __________ until the Proterozoic Eon, when cyanobacteria released _____________ into the air during the process of photosynthesis
Paleozoic
The ________________ Era began about 540 million years ago as the global supercontinent Pannotia was breaking up
Pangaea
the formation of a new supercontinent, ___________, began during the Paleozoic
Mesozoic
The _______________ Era began about 250 million years ago after the Permian mass extinction
dinosaurs
Life during the Mesozoic era was dominated by ____________
Cenozoic
The ____________ era began about 65 million years ago with the Cretaceous mass extinction and continues to the present.
Quaternary
Evolution of modern humans occurred during the late ___________________
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