Relative Age Flashcards
What are two schools of thought about how old the earth is?
Catastrophism, Uniformitarianism
In the field of thought called ________ people thought that large-scale geologic features formed in catastrophic events
catastrophism
What two ideas did Catastophists believe about the Earth/
- large-scale geologic features formed in catastrophic events
- the age of Earth was measurable in human historical terms
which field of thought is accepted by much of the scientific community?
uniformitarianism
Uniformitarianism says that past and present _____ processes are similar
geologic
Uniformitarianism says that…
past and present geologic processes are similar
This field of thought says that past and present geologic processes are similar?
uniformitarianism
When we say that past and present geologic processes are similar, we mean that…
we can look at geologic processes that are occurring today and backtrack and assume that they are similar to the processes that have operated throughout earths history
Since today we don’t see large-scale catastrophes occurring not the face of he earth, what can we assume?
we can assume that these did not happen in Earth’s past either, rather its the thought that Earth’s processes move more slowly and the earth is much much older than the span of human history
Do Earth’s processes move slow of fast?
slow
what does uniformitarianism propose?
Earth was ancient much beyond the span of human history
What is relative age?
looking at two different things and broadly comparing there ages.
Relative age is looking at two different things and _______ there ages
comparing
when determine the relative age of two different things do we find the precise number or age of them?
NO
We determine which events happened first, second, third, etc.
Stratigraphy is…
the science of looking at different layers of rocks the processes that form those layers
the science of rock layers and strata-forming processes
Stratigraphy is the science of _____ layers and strata-forming ______
rock, processes
There are a couple different ______ developed through stratigraphy laws that help us to determine the relative age of rock layers
laws
What does the law of original horizontality say?
sedimentary beds or strata laid in water are laid horizontally.
This law says that sedimentary beds or strata laid in water are laid horizontally.
law of original horizontality
The law of original horizontality says that sedimentary beds or strata laid in water are laid ________
horizontally
when sediment is deposited at the bottom a lake, the sediment accumulates in _________ layers
horizontal
The law of original horizontality applies mostly to…
sedimentary rocks
If you see layer that are angled or curved, there must have been some ______ that ______ those layers from their original deposition
event, altered
Under the law of original horizontality, what can we infer from observing an angled or curved sedimentary layer?
there has been some event that altered those layers from their original deposition
What does the principle of superposition state?
that in undisturbed strata or layers, younger layers are deposited above older ones.
The principle of superposition states that in undisturbed strata or layers, _______ layers are deposited above ______ ones.
younger, older
which principle/law states that in undisturbed strata or layers, younger layers are deposited above older ones?
law of superposition
What does the principle of cross-cutting relationships state?
that any feature cutting through or disrupting a layer is younger than the layer itself.
What does the principle of cross cutting relationships mainly apply too?
faults and dikes
a fault must be younger then the layers of rock because the layers of rock had to have been deposited _______ in order for the fault to displace them
first
Is a fault younger or older than the layer is disrupts?
younger
Due to acts of _______ some layers are ______ away and wiped out of the geologic timeline
erosion, eroded
as we look at layers of rocks we sometimes can get a pretty good ______ of the geological events that occurred in that area, we can see year to year the sediment that was deposited, the types of rocks, the types of environments.
history/picture
Missing layers erased from the geologic timeline by erosion are called…
unconformities
unconformities are a _____ in the sequence of rock layers
gap
What are unconformities?
gaps in the sequence of rock layers
what are the three different kinds/types of unconformities?
- nonconformity
- Angular unconformity
- disconformity
Nonconformity is…
a sedimentary layer next to igneous or metamorphic layer
all unconformities are ______ before two beds
boundaries/lines
a nonconformity is the _____ or ____ that separates sedimentary rocks from non-sedimentary rocks
line, layer
what does nonconformity signal?
that you have a gap in the sequence because we can assume that the igneous rock came though and melted whatever sedimentary rocks originally deposited
Angular nonconformity is…
the line that marks the boundary between angled beds and horizontal beds
What is a disconformity?
Any general erosional surface
The line that indicates that any erosion has occurred is called….
a disconformity
The principle of of Faunal Succession states that…
different rock layers from different ages will contain unique fossil assemblages
which principles states that different rock layers from different ages will contain unique fossil assemblages?
principle of faunal successions
Since the fossil record is pretty much established, what can we determine?
which rocks are older then the others by looking at the fossils that are in them
The principle of faunal succession states that different ______ layers from different _____ will contain unique fossil _______
rock, ages, assemblages
Fossils can be used to determine that rock _____ from different ______ have the same ____, or were formed in the same event
units, locations, age
