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An igneous rock was formed with 8000 radioactive
(parent) atoms but contains only 1000 radioactive
(parent) atoms today. If the half-life for the
radioactive element is 10 million years, the rock is ___
million years old. -
Correct Answer-30
Which of the common components of siliciclastic
sediment are likely to have been formed from the
original sediment source rock through chemical
weathering? -
Correct Answer-clays
Which is the largest division of geologic time? -
Correct Answer-eons
Which process causes subsidence in a sedimentary
basin? -
,Correct Answer-both deposition of sediments and regional
downfaulting
What is a nonconformity? -
Correct Answer-a gap in the geologic record bounded
below by metamorphic or igneous rocks and bounded
above by sedimentary rocks
The study of the history of ancient life based on the
fossil record is called: -
Correct Answer-Paleontology
The remains of algae, bacteria, and other organic
material may accumulate as organic matter on the
seafloor that can be transformed into: -
Correct Answer-oil and gas
Why does mechanical weathering of an exposed rock
cause chemical weathering to take place more
quickly? -
Correct Answer-broken rock fragments have more
exposed surface area
Which of the following is a clastic sedimentary
environment? -
,Correct Answer-alluvial
Which is the most common type of chemical or
biological sedimentary environment? -
Correct Answer-carbonate environment
The half-life of a radioactive material depends on: -
Correct Answer-the half-life is constant for any one
material
The Precambrian represents about what fraction of the
age of Earth? -
Correct Answer-90%
What is the geologic time scale? -
Correct Answer-a division of Earth's history into time
intervals beginning and ending at times when fossils
changed significantly
What is NOT an example of physical weathering? -
Correct Answer-dissolution of some minerals in a rock,
causing it to weaken
, Why does most of our information on geologic history
come from continental rock? -
Correct Answer-oceanic crust older than 200,000,000
years has been recycled by subduction
What type of event might lead to the development of
an unconformity? -
Correct Answer-sea level drops
Cross-bedding forms on ___ of a sand dune -
Correct Answer-the downwind side
How do most carbonate sediments and rocks in
shallow environments form? -
Correct Answer-they are bioclastic materials
Coal is formed from: -
Correct Answer-peat
What process must occur before an intrusive igneous
rock can be weathered? -