Earth science topic 13
The following diagram represents a crosssectional view of a portion of earth's crust showing sedimentary rock layers that have not been overturned. The letters identify specific layers. Which rock layer is probably the oldest?
A
Which is the most recently formed rock?
A
An unconformity is located between
C and d
Why is carbon-14 usually not used to accurately date objects more than 50,000 years old?
Carbon-14 has a relatively short half-life, and too little carbon-14 is left after 50,000 years
The following diagrams represent cross sections of three areas of exposed bedrock approximately 100 km apart. What would be the best method of correlating the rock layers of each area?
Comparing index fossils
Which is the oldest sedimentary rock in this diagram?
Conglomerate
The conclusion that the limestone layer d is younger than the basalt layer e is supported by evidence of
Contact metamorphism
The best basis for concluding that a certain layer of shale rock in New York State was deposited at the same time as one in California is that both
Contain similar fossil remains
Because of the half life nature of the decay process, uranium 238 will theoretically
Continue to decay indefinitely
The last event before faulting occurred was the formation of
D
Rock layer b is the same age as layer
F
The disturbed rock structure shown is probably the result of
Faulting
Fossils are rarely found in Precambrian rocks because, at that time
Few life forms had hard parts
The simplest way to correlate exposed rock layers in the same general vicinity when they contain no fossils is by
Following the continuity of the layers
The geologic time scale has been subdivided into a number of time units largely on the basis of
Fossil evidence
Approximately 3.5 billion years ago photosynthetic organisms evolved. What dramatic change in earth's atmosphere resulted primarily from this event?
Free oxygen builds up in the atmosphere
Because the chemical, physical, geological, and biological characteristics of nature remain the same throughout time, we can interpret the past and
Identify uncomforities
Which must have most recently preceded the formation of layer d?
Intrusion
The half-life of a particular radioactive substance
Is independent of mass, temperature, and pressure
The following diagram shows a portion of earth's crust. What is the relative age of the igneous rock?
It is younger than the limestone but older than the shale
Escribe two essential characteristics of an index fossil
Live for a short amount of time, has a wide horizontal distribution or is a single species of life
According to the generalized bedrock geology of New York State in the earth science reference tables, what is the geologic age of the bedrock found at the surface at 43 degrees 30 north latitude by 75 degrees west longitude?
Middle proterozoic
The changes observed in th fossil record from the Precambrian to the Cenozoic era best provides evidence of
Organic evolution
If a specimen of a given radioactive substance is reduced in size, it's half-life
Remains the same
According to the earth science reverence tables, which rock is most likely the oldest?
Shale containing trilobite fossils
What is the age of the surface bedrock at niagra falls, New York?
Silurian
Which area in New York State is located on rock formations that contain large amounts of deposits?
Syracuse
Why might it be more likely for a fossil to be found in a sedimentary rock than in either an igneous or metamorphic rock?
The high heat associated with igneous and metamorphic rocks would destroy any evidence of life
The following diagram represents exposed bedrock. Which geologic event occurred last?
The intrusion of A
,in a conglomerate rock sample that is composed of limestone particles cemented together by calcite, what is the oldest part of the rock sample?
The limestone particles
Shark and coral fossils are found in the rock record of certain land areas. What does the presence of these fossils indicate about those areas?
They were once covered by shallow seas
"The present is the key to the past" explain what this statement means in the context of geologic history
Things in science stay the same throughout time, therefore they can predict things about the future using things they know about the past
The following diagram represents a cross-section of earth's crust. The symbols in the diagram indicate the location on a horizontal surface of certain fossils that formed during the Carboniferous period. For what purpose would the fossil formation on the map be most useful?
To find the location of the shoreline during the Carboniferous period
Some uranium is obtained from an intrusive granite formation. It is then analyzed and found to contain approximately 1 gram of lead-206 to every 3 grams of uranium-238. Approximately how many billions of years old is the granite?
Two
An uncomfortable between two sedimentary layers is most likely produced by
Uplift followed by extensive erosion, submergence, and deposition
Why can layers of volcanic ash found between other rock layers often serve as good geologic time markers?
Volcanic ash usually is rapidly deposited over a large area
Which radioactive substance shown on the following graph has the longest half-life?
D
Carbon-14 is often used to date fossils from the Holocene epoch why would carbon-14 be less useful in dating an Ordovician fossil?
It has a small half life
Suppose you are examining a section of sedimentary rock. What evidence could you observe that would support the principle of superposition?
Use index fossils or radioactive decay dating to indicate that the age of the rocks gets younger toward the top
If the decay curve for the element carbon-14 were plotted, which diagram shows the general shale that the curve would be?
2
Which curve represents the expected decay rate of uranium-238 if it's temperature were raised almost to the melting point
2
The following diagram of three profile sections show fossil deposits w, x, y, and z found at widely separated locations. Which would be the best index fossil?
2) x
The following diagrams represent the rock layers and fossils found at four widely separated area of exposed bedrock. Which fossil appears to be the best index fossil?
3
Which line is the best representation of the relative duration of each of the geologic time intervals
4
The half life of uranium-238 as shown on this graph is closest to
4.5 billion years
According to the geologic history of New York State in the earth science reference tables, what is the estimated age of earth as a planet in millions of years?
4600
Approximately how long ago were the taconic mountains uplifted?
470 million years ago