geologic history
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what does an unconformity represent
time gap in the record of the area
why are ancient volcanic ash deposits important to geologists
the serve as good geologic time markers
living corals are found in warm shallow seas. coral fossils are found in the sedimentary rocks of Alaska. what does this suggest?
Alaska once had a tropical marine environment
unless a series of sedimentary rock layers is overturned the bottom layer is usually…
older
which feature in a rock layer is older than the rock layer
rock fragments
the fossil record indicates that most plants and animals that lived on Earth in the past….
have been extinct
what are two ways to date rocks
relative age absolute age
relative age example
correlation
principle of superposition
sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it
unconformity
buried erosion surface separating two rock masses or strata of different ages
what does unconformity indicate
sediment deposition was not continuous
correlation
rocks or geology events from different places are determined to be the same age or similar
3 methods of correlation
similarities in rocks index fossils volcanic ash/ meteorite deposits
what are some characteristics of an index fossil
large horizontal distribution small vertical distribution
horizontal distribution
how big the fossil’s geographic range is
vertical distribution
how long it lived
what does all matter in the universe contain
atoms
Atomic number
the number of protons
mass number
number of protons and neutrons
isotopes
elements that have differing mass numbers
what is an example of an isotope
c-12 contains 6 protons and 6 neutrons
what is the mass number of c-24
12 protons and 12 neutrons
are isotopes radioactive
yes
do heat and pressure affect isotopes
no