If the same index fossil is found in different areas, the strata in each area were likely deposited at the same time. Thus, the principle
of faunal succession
makes it possible to determine the relative age of unknown fossils and correlate fossil sites across large discontinuous areas.
What does it mean if fossils are found in the same layer?
Certain widely found fossils represent animals that only lived on Earth for a very short time. Such fossils are called
index fossils
. When found in two geographically separated layers, they allow scientists to say, with some confidence, the layers are the same.
What can rock layers tell us about the fossils that are found in them?
Fossils found in a particular rock layer
help scientists determine the age of the rock
. Scientists use a technique called radiocarbon dating to find out the age of the fossils. Once they know the age of the fossil in the rock, they also know that rock itself is about the same age!
What indicates when index fossils are present in rock layers in different areas of the world?
Index fossils are present in rock layers in different areas of the world indicated
the rock layers formed during different periods of time and the rock layers are still forming
. Explanation: Index fossils are fossils of organisms that lived during only one short period of time.
Are index fossils only found in one rock layer?
Short Lived = Within each outcrop,
the fossil can only appear in one layer
(row). To find the index fossil you must eliminate any fossils that don't show up in each rock outcrop and those that show up in more than one layer per outcrop.
How are fossils found in different rock layers of the earth?
Animal remains are most likely to be fossilized if
their hard parts are covered by layers of sediments soon after death
. With time and pressure, these sediments, such as sand, plant debris, or ash, become compressed into rock. Therefore, fossils are found in sedimentary rock, like sandstone, shale, limestone and coal.
How can we tell which layers of fossils are older than others?
To get an age in years, we use
radiometric dating of the rocks
. Not every rock can be dated this way, but volcanic ash deposits are among those that can be dated. The position of the fossils above or below a dated ash layer allows us to work out their ages. The volcanic ash layer is dated as 507 million years old.
What is the oldest rock layer?
Over time, the sediments pile up to form horizontal layers of sedimentary rocks.
The bottom layer of rock forms first
, which means it is oldest. Each layer above that is younger, and the top layer is youngest of all.
Are rocks harder than fossils?
The paleontologist tells you that the fossil may be a different color than the rock and that
the fossil is usually harder than the rock
. The fossil bone will also have a different texture than the rock. … That's the remnants of the internal bone structure.
Why are there no fossils in some layers?
4. Why are there no fossils in layers C and E?
There was a lava flow so the lava probably destroyed any fossils that were in those layers
.
Which best describes the relationship between rock layers and index fossils?
Which best describes the relationship between rock layers and index fossils? …
Different rock layers can be determined to be the same relative age if they contain the same index fossils
.
Which index fossil is the oldest?
The law of superposition states that each
rock
layer is older than the one above it. So, the relative age of the rock or fossil in the rock or fossil in the rock is older if it is farther down in the rock layers.
Will humans be a good index fossil?
Some fossils are more useful than others in establishing the age of rocks. These are called index fossils. …
It is possible that humans also will be good index fossils at some time in the distant future
. Humans have distinct hard parts, and we often bury our dead.
What are the four characteristics of index fossils?
A good index fossil is one with four characteristics:
it is distinctive, widespread, abundant, and limited in geologic time
. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms. That being said, certain land organisms are useful in young rocks and specific regions.
Why do we use index fossils instead of all fossils when trying to determine rock age?
Certain fossils, called index fossils, help geologists match rock layers. To be useful as an index fossil, a fossil must be widely distributed and represent a type of organism that existed for a brief time period. Index fossils are useful
because they tell the relative ages of the rock layers in which they occur
.
What two traits are present index fossils?
A useful index fossil must
be distinctive or easily recognizable, abundant
, and have a wide geographic distribution and a short range through time.
