3/2/24 EARTH SCIENCE UNIT 5 EXAM Flashcards
deep time
it refers to the time scale of geologic events
what is the difference between relative and absolute time?
relative time is the age of events in a sequence (oldest to youngest, no numbers), absolute time is the identification of events by a number
geological cross-section
is a side view of exposed rock layers which is drawn with symbols to indicate different rocks
law of superposition
the oldest rock layers are found at the bottom and the youngest layers are found at the top
law of cross-cutting relationships
the rocks had to have formed first before geological processes have affected the rocks, ex: a fault is younger than the rocks that broke in the faulting
law of original horizontality
the rocks had to have formed first, in order for geologic processes to have affected them after
law of included fragments
the rocks had to have formed first, in order for geologic processes to have affected them after
law of folding/tilting
the rocks had to have formed first in order for geologic processes to have affected them after
uncomformity
an old buried surface that was eroded, overtime new rock layers were deposited on top of it, the erosion erases some of the rock layers, creating a “gap” of missing geologic time, like millions of years
what are the three types of unconformities?
disconformity, angular unconformity, and nonconformity
what is the siccar point?
an angular unconformity in Scotland that consists of sedimentary rocks, gray sandstone, red sandstone and proves the unconformity theory
disconformity
an erosion surface between two packages of sediments, but the lower package of sediments was not tilted prior to deposition of the upper sediment package
noncomfortmity
are unconformities that separate igneous or metamorphic rocks from overlying sedimentary rocks
angular unconformity
are those where an older package of sediments has been tiled, transacted by erosion and than a younger package of sediments was deposited on this erosion surface
law of uniformitarism
is a law stating that geologic processes that are acting presently are the same processes that have changed Earth in the past
erosion
geological processes in which materials are worn away by natural causes such as wind
tilting
a change in attitude of any portion of the Earth’s surface
faulting
fracture or zone fractures between two blocks of rock
contact metamorphism
a type of metamorphism where rock minerals and texture are changed, mainly by heat, due to contact with magma
half life
the time required for one half of the radioactive (parent) isotopes in a sample to decay to radiogenic (daughter) isotopes
isotope
atoms of the same elements contain different numbers of neutrons
parent product
results from the decay of a parent
radiometric dating
the abundances of parent and daughter isotopes in a sample can be measured and used to determine their age
radioactive decay
is useful because each half life takes the same time approximately as the next one therefore it is reliable to obtaining absolute ages for rocks
element
the simplest form of matter that has a unique set of properties
parent isotope
an unstable isotope that will undergo radioactive decay
what do atoms of a given element always contain?
the same number of protons
isotope
atoms of an element with different numbers of neutrons are called protons
how does carbon-14 get in our bodies?
carbon-14 forms when cosmic rays form neutrons in the atmosphere, these neutrons collide with nitrogen-14 which is one of the most common gasses in the atmosphere
what is carbon 12?
carbon 12 is the form of carbon that are almost all atoms on Earth
radiometric dating
the rate of decay of unstable isotopes can be used to estimate the absolute ages of fossils and rocks
radio carbon dating
the best known method of radiometric dating is carbon 14 dating
when is carbon 14 super useful?
carbon 14 is super useful when trying to date organic remaining
how does radio carbon dating works?
a living thing takes in carbon-14, along with stable carbon-12, through photosynthesis is and the food web. As the carbon-14 decays it is replaced with more carbon-14. After the organism dies it stops taking in new carbon. The carbon-14 that is in its body contains to decay into nitrogen-14, which is lost to the atmosphere. So the organism decreases less and less carbon014 as time goes on, while the stable carbon-12 remains in place
