Test 2 Flashcards
Geologists are able to identify and separate different periods of geologic time by studying the fossil record within rock layers, using a technique called “____ ____,” which analyzes the position of rock layers to determine which ones are older or younger based on the principle of superposition.
Relative Dating
___ is the action of placing one thing on or above another, especially so that they coincide
Superposition
___ age refers to the age of something compared to other things, indicating only whether it is older or younger
Relative
___ age is the exact numerical age of something, measured in years, providing a specific time frame for when something existed
Absolute
The principle of ___ ___ states that layers of sediment are originally deposited in flat, horizontal layers parallel to the Earth’s surface
Original horizontality
The principle of ___ relationships is a geological principle that states that a geological feature that cuts through another feature is younger than the feature it cuts
Cross-cutting
The principle of ___ states that if a rock fragment (inclusion) is found within another rock, the inclusion must be older than the rock that contains it
Inclusions
Four geologic eras in order (oldest to most recent)
Precambrian, Paleozoic, Mesozoic, Cenozoic (Pr, Pa, M, C)
Four geologic eras in order (oldest to most recent)
Precambrian, Paleozoic, Mesozoic, Cenozoic (Pr, Pa, M, C)
What era is the quaternary period in?
Cenozoic
What era is the palaeogene period in?
Cenozoic
What era is the Cretaceous period in?
Mesozoic
What era is the Jurassic period in?
Mesozoic
What era is the Triassic period in?
Mesozoic
What era is the Permian period in?
Late Paleozoic
What era is the Carboniferous period in?
Late palaeozoic
What era is the Devonian period in?
Late palaeozoic
What era is the Silurian period in?
Early palaeozoic
What era is the Ordovician period in?
Early palaeozoic
What era is the Cambrian period in?
Early palaeozoic
What epoch/period was advanced civilization recorded for the first time? Hint: in the Cenozoic era + 11,700 years ago
Holocene
What epoch/period was the most recent ice age? Hint: in the Cenozoic era + 2.6 million years ago
Pleistocene
What epoch/period was the K-T (dinosaur) extinction? Hint: in the Mesozoic era + 65 million years ago
Creatceous
What epoch/period was the Atlantic Ocean formed? Hint: in the Mesozoic era + 150 million years ago
Jurassic
What epoch/period was Pangaea formed? Hint: in the Mesozoic era + 300 million years ago
Jurassic
What epoch/period was the Age of Coal Forests in? Hint: In the Paleozoic Era + ~290 million years ago
Carboniferous
Which epoch/period was the Age of Fishes in? Hint: in the Paleozoic Era + ~419 million years ago
Devonian
What epoch/period was the Cambrian Explosion in? Hint: in the Paleozoic Era + ~485 million years ago
Cambrian
During what eon was the first life? Hint: in the Precambrian Era + ~2.5 billion years ago
Archean
During what epoch/period was the first “oxygenation event?” Hint: in the Precambrian Era + ~2.4 billion years ago
Proterozoic
During what epoch/period is the oldest known rock from? Hint: in the Precambrian Era + ~4 billion years ago
Hadean
During what epoch/period was Earth formed? Hint: in the Precambrian Era + ~4.5 billion years ago
Hadian
What happens when an atom has experienced radioactive decay?
It transforms into a different atom, usually a more stable one
___ is primarily used to date organic materials like fossils or wood
Carbon-14
___ is used to date older rocks, like igneous rocks
Uranium-235
How is uranium-235 used to date rocks?
By measuring the ratio of the radioactive parent isotope (uranium) to its stable daughter product (lead) as it decays over time.
The more ___ product present, the older the rock is
Daughter
How is carbon-14 used in carbon dating?
It is used by measuring the amount of carbon-14 remaining in an organism after it dies. Carbon-14 gradually decays at a known rate (half-life), allowing scientists to estimate how long ago the organism lived
What is the radioactive half-life of an element?
The amount of time it takes for exactly half of the atoms in a sample of that element to decay into another element through radioactive emission (aka: the time it takes for the radioactivity of a sample to decrease by half)
What equation can be used to predict what fraction of an original radioactive sample should remain in a rock after a certain number of half-lives?
(1/2)^n where “n” represents the number of half-lives that have passed; meaning after one half-life, half of the original sample remains, after two half-life’s, only a quarter remains, and so on
How do you use the ratio of parent to daughter atoms in a rock to find its age, given in number of half-lives?
By measuring the ratio of parent to daughter atoms in a rock, and knowing the half-life of the radioactive parent isotope, you can determine the age of the rock in terms of the number of half-lives that have passed (aka: the ratio directly reflects how many half-lives have elapsed since the rock formed
