Rock Layers & Dating
What is the Law of Superposition?
(A: The oldest rock layers are at the bottom, and the youngest are at the top.)
What is an index fossil?
(A: A fossil from a species that lived for a short time and is found worldwide.)
True or False: Most fossils are found in sedimentary rock.
T
Explain how absolute age of volcanic ash and relative age can be used to help scientists find the age of fossils.
By using unstable particle dating (radiometric) dating to find the exact age of volcanic ash layers and then comparing that with the fossil.
How do fossils help scientists understand the past?
(A: They show changes in Earth’s climate and life forms over time.)
What do scientists compare to determine the relative ages of rocks?
(A: Rock layers)
Name one reason why index fossils are useful to scientists.
(A: They help determine the age of rock layers.)
True or False: It is rare for the remains of a soft-bodied organism to become a fossil.
True
Describe the process of absolute dating as it relates to igneous rock and the fossil record.
By using unstable particle (radiometric) dating to determine the exact age of igneous rock layers associated with fossils.
How do fossils help scientists match rock layers from different locations?
(A: If the same fossils appear in different places, the rock layers are likely the same age.)
What is the difference between relative dating and absolute dating?
(A: Relative dating compares rock layers, while absolute dating determines exact ages using radioactive elements.)
Earth is approximately 4.6 billion years old. How do scientists determine this?
using absolute dating techniques
True or False: The fossil record represents less than one percent of all of the species that ever lived.
True
How does an index fossil record assist in determining the age of other fossils?
By providing a reference for the time period in which it existed, helping to date other fossils from the same era.
Why are mammoth fossils important in understanding Earth’s climate?
(A: They show that parts of Earth were once much colder than today.)
Why do deeper rock layers contain older fossils?
(A: Older layers were buried first, so their fossils are older.)
What happens if an index fossil is found in two different rock layers far apart?
(A: The rock layers are likely the same age.)
How does relative dating help determine the age of a fossil?
It determines whether a fossil formed before or after another fossil.
Jacob has one older brother and one younger sister. He wants to explain relative dating to them using their ages as an example. Which statement describes their ages using relative dating?
Jacob is younger than his brother but older than his sister.
Why are fossils usually found in sedimentary rock rather than igneous rock?
(A: Sedimentary rocks form from layers of sediment where organisms can be buried and preserved, while igneous rocks are formed from molten lava.)
What could cause rock layers to appear out of order?
(A: Events like earthquakes, erosion, or folding of rock layers.)
True of False: Land organisms are more likely to fossilize than aquatic organisms.
F
Juan is studying fossils. His teacher wrote the following statements on the board and asked the students to put them in the correct order to describe how fossils are formed.
1. Layers of sediment finally bury the entire skeleton.
2. Sediment builds up and over time turns to rock.
3. An organism dies, and its body begins to decompose.
4. Sediment begins to cover the organism’s skeleton.
Which is the correct order of events for fossil formation?
3, 4, 1, 2
Mr. Lien is 73 years old. What kind of dating is this?
Absolute
What type of fossils help scientists understand ancient animal environment?
fossils of specific plants and animals