Unconformities are a type of geologic contact—a boundary between rocks—
caused by a period of erosion or a pause in sediment accumulation, followed by the deposition of sediments anew
.
Which statement explains one reason why unconformities occur rocks along a fault break and move igneous rock forms at Earth’s surface no sediment is deposited over a long time igneous rock forms between sedimentary layer?
Answer: An unconformity is
a buried erosional or non-depositional surface separating two rock masses
or strata of different ages, indicating that sediment deposition was not continuous.
What explains one reason why unconformities occur?
Which statement explains one reason why unconformities occur? Rocks along a fault break and move. …
Igneous rock forms between sedimentary layers. No sediment is deposited over a long time.
What do unconformities indicate?
Nonconformities are unconformities that separate igneous or metamorphic rocks from overlying sedimentary rocks. They usually indicate that
a long period of erosion occurred prior to deposition of the sediments
(several km of erosion necessary).
In which situations is the principle of cross-cutting relationships?
According to the principle of cross-cutting relationships,
the geological features that cuts another rock formation are younger in age, than the formation it cuts
. For example, magma intruding from the depth in a region of sedimentary rocks describes that the intruding magma is younger in age than the country rocks.
The correct answer is –
All are younger than surrounding rocks
. Explanation: In comparison to surrounding rocks the intrusion, extrusions and faults are the much younger.
Which is the first step that geologists must do?
Answer: The first step a geologist would take in order to compare rock layers at distant locations is
to Assign a date to the rock layers
.
How is radioactive decay used to date sedimentary rocks?
How is radioactive decay used to date sedimentary rocks?
The amounts of unstable elements in the volcanic layers above and below the sedimentary layers are measured
. … Geologists determine half-life as radioactive elements get trapped in rock and break down over time.
How do index fossils help scientists quizlet?
Index fossils help
scientists match rock layers
. Two rock layers in different places that contain the same index fossil are about the same age. Index fossils are useful because they tell the relative ages of the rock layers in which they are found.
How is a nonconformity formed?
Nonconformity:
develops where sediments are deposited on top of an eroded surface of igneous or metamorphic rocks
. Paraconformity: strata on either side of the unconformity are parallel, there is little apparent erosion. Angular unconformity: strata is deposited on tilted and eroded layers (such as at Siccar Point)
What two factors can cause an unconformity to occur?
Unconformity Defined
Unconformities represent gaps in the geologic record, periods of time that are not represented by any rocks. Unconformities happen for two reasons:
sediment deposition stopped for a considerable time and/or existing rocks were eroded prior to being covered by younger sediment.
How many types of unconformities are there?
There are
four types
of unconformities. Disconformities are those that occur between sedimentary rocks. Nonconformities are parallel nonconformities between sedimentary and igneous rocks. Angular conformities are those with parallel sedimentary layers that have been deposited over sharp, angular sediments.
In which situation is the principle of cross cutting relationships useful in determining age?
correct answer is: A fault breaks through sedimentary layers. Explanation:
Formation of an intrusion in the earth’s surface and igneous rock that forms between sedimentary layers
are examples of situations where the principle of cross cutting relationships is useful in determining relative age.
How do index fossils help scientists?
Index Fossils – are fossils that must be widely distributed and represent a type of organism that existed only briefly. Index fossils are
useful because they tell the relative ages of the rock layers in which they occur.
Which statement about how geologists study the ages of rock layers is true quizlet?
Which statement about how geologists study the ages of rock layers is true?
The law of superposition means that older rocks are on top
. Geologists can find the exact age of a rock by looking at its relative position. The principle of original horizontality provides the basis for the law of superposition.
Are intrusions and extrusions faults?
Explanation: The features extrusion, intrusion and faults are
the features of the surrounding rocks
. The extrusion and intrusions are the features of the igneous rocks. … The faults are cracks that are formed on the crust these are formed on the preexisting rocks.
