Index fossils are used in biostratigraphy to correlate rocks from different loca
ID: 286952 • Letter: I
Question
Index fossils are used in biostratigraphy to correlate rocks from different locations. Which of the following is not trait of an index fossil? O The organism lived for a short time period. O The fossil is easily identifiable. a The presence of the fossils causes seismic energy to move very quickly through the rocks. d) The organism was distributed across large areas. QUESTION 3 Type sections are rocks that e are made up of the same rock type e have a thin layer of ash that was deposited after a volcanic eruption are separated by an unconformity o are distinct to a certain location, and can be used to determine the age of rocks from other areas based on similar fossils or other indicators QUESTION 4 e of potassium-40 is 1 billion s 3 billion years old, how many potassium-40 atoms did it Potassium-40 undergoes radioactive decay and produces argon-40. Assume the half-if years. if a rock today has 100 atoms of potassium-40 and have when it formed? O 800 300 200 D 50Explanation / Answer
Q.2) Index fossils are used in biostratigraphy to correlate rocks from different locations. Which of the following is not a trait of an index fossil ?
Ans. The presence of the fossil causes seismic energy to move very quickly through the rocks.
All other options are trait of an index fossil .
Q.3) Type sections are rocks that_________.
Ans. Are distinct to a certain location, and canbe used to determine the age of rocks from other areas based on similar fossils or other indicators.
Q.4) Potassium-40 undergoes radioactive decay and produces argon-40. Assume the half-life of potassium-40 is 1billion years. If a rock today has 100 atoms of potassium-40 and is 3billion years old, how many potassium-40 atoms did it have when it formed ?
Ans. 800.
Half-life of potassium-40 is 1billion years. So, at this time half of the parent atoms remain.
After 2billion years 1/4 th of the parent atoms remain.
And after 3billion years 1/8 th of the paret atoms remain.
So, according to given question 100 atoms is the 1/8 th part of the initial parent atom.
Initial parent atom is 800.
So, there is 800 potassium-40 atoms did it have when it formed.