Geological Time
A rock formed with 1,000 atoms of a radioactive parent element, but only contains 250 radioactive parent atoms today. If the half-life is 1,000,000 years, how old is the rock?
2,000,000 years
Atoms of AA decay to atoms of BB with a half-life of 100,000 years. If there are 20,000 atoms of AA to begin with (and 0 atoms of BB), how long will it take for there to be 2,500 atoms of AA?
300,000 years
use radiometric dating techniques to determine how long ago the rock formed in the exact number of years
Absolute dating
Human beings evolved during which geologic era?
Cenozoic
Mammals became abundant during the ________Era?
Cenozoic
establishing the equivalence of rocks of similar age in different areas
Correlation
when two sedimentary rock layers are separated by an erosional surface.
Disconformity
The person given the title "the father of geology" is
James Hutton
The Paleozoic does not include the
Jurassic
Which law says that the oldest rocks will be at the bottom and the youngest at the top?
Law of Superposition
Large reptiles became abundant during the ________Era?
Mesozoic
The _________ was an era dominated by the dinosaurs
Mesozoic
when the erosional surface separates older metamorphic or intrusive igneous rocks from younger sedimentary rocks
Nonconformity
Land plants appeared during the ________Era?
Paleozoic
Which of the following represents the longest time period
Precambrian
Any feature (e.g. fault or intrusion) that cuts across rocks is younger than the youngest rock that is cut.
Principle of Crosscutting Relationships
Fossil content of rock changes in a systematic way, reflecting evolutionary changes
Principle of Faunal Succession
Sedimentary layers are deposited in approximately horizontal sheets.
Principle of Original Horizontality
Rock layer above is younger than the ones below it.
Principle of Superposition
Which of the following statements regarding radiometric dating is false?
Radioactive elements are only found in living things
Radioisotopes are trapped in minerals when they crystallize. Radioisotopes decay through time, and stable isotopes are formed. Determining the ratio of parent isotope to daughter product reveals the number of half-lives that has elapsed.
Radiometric Age Dating
Unconformities are surfaces in rock that represent periods of erosion or non-deposition
Unconformities
whatever processes are occurring today (plate tectonics, volcanism, mountain building, earthquakes, sedimentation) also occurred in the past and probably at the same (or very comparable) rates.
Uniformitarianism
Radiometric age is often referred to as __________ age
absolute
during the pause in deposition, a period of deformation (folding or tilting) and erosion occurred.
angular unconformity
Which of the following isotopes is most useful for dating the bones from a mammal fossil that was found not too far down from the surface?
carbon-14
Which of the following radioactive isotopes has the shortest half-life?
carbon-14
Which of the following radioactive isotopes is most useful for dating a very young sample (<20,000 years) of wood?
carbon-14
Which of the following will not make a fossil
decomposed organic material
The boundaries between _______ seem to coincide with major changes in the life forms present on Earth.
eras
Most periods in the geologic time scale are named for
geographic localities
time it takes for one-half of the radioactive material to decay
half life
In the past there were (more or less) atoms of radioactive Uranium? (Hint: half-life of Uranium is in the billions of years and you start with 100% of the radioactive substance so...)
more
A sedimentary rock layer is __________ than the layer above and _______ than the layer below.
older --- younger
What scientific avenue of investigation gave scientists the best estimate of the age of the Earth?
radiometric dating
determine whether the rock is older or younger than other rocks
relative dating
Which of the following radioactive isotopes has the longest half-life?
rubidium-87
Fossils are most common in which rock types?
sedimentary
Radiometric dating is least useful for ___________ rocks.
sedimentary
We cannot accurately measure time in years with stratigraphy for several reasons. Which of the following is false.
sediments accumulate at different rates in different sedimentary environments
The Law of cross cutting relationships ___________ .
states that an igneous intrusion is younger than all the layers it cuts through
What are properties of index fossils?
stratigraphy fossils cross-cutting relationships
Potassium-Argon (K-Ar) age measures _________
the time since crystallization of a mineral containing Potassium
This picture represents one of the most ancient and widespread index fossils. It is known as a _______.
trilobite
A missing section of the rock record is a(n)
unconformity
Which of the radioactive elements below has the greatest mass?
uranium-238
A stratigraphic sequence is a vertical set of strata
used as a chronological record of the geologic history of a region