Vocabulary
The breakdown of a radioactive isotope into a stable isotope of the same element is called:
Radioactive decay
In what way are eras different from periods?
They are longer spans of time
This divides Earth's history into intervals of time defined by major events or changes on Earth.
Sandra is making a poster of Earth's geologic history. She wants to include a timeline on her poster. Which date should Sandra use at the beginning of her timeline, to show Earth's formation in the solar system?
1. 3.5 million years ago
2. 700 million years ago
3. 4.6 billion years ago
4. 12 billion years ago
c: 4.6 billion years ago
This divides Earth's history into intervals of time defined by major events or changes on Earth.
Geologic time scale
Determining the actual age of an event or object in years is called:
Absolute dating
The geologic time scale is divided by several different spans of time. Which of the following divisions of time are all eras?
1. Cretaceous, Jurassic, Triassic
2. Paleocene, Eocene, Oligocene
3. Cenozoic, Mesozoic, Paleozoic
4. Precambrian, Cambrian, Devonian
3: Cenozoic, Mesozoic, Paleozoic
The time needed for half of a sample of a radioactive substance to undergo radioactive decay and form daughter isotopes.
Which of these choices is the best definition of absolute dating?
1. Finding the age of an object compared to other objects.
2. Measuring the age of an object in years using any method.
3. Determining the amount of a radioactive isotope in an object.
4. Determining the age of a rock layer by studying the fossils present.
B: Measuring the age of an object in years using any method.
An ordered arrangement of rock layers that is based on the relative ages of the rocks, with the oldest rocks at the bottom of the column.
Geologic column
Finding the relative age of a sample by determining the relative percentages of a radioactive parent isotope and a stable daughter isotope is called:
Radiometric dating
What is the main criterion that scientists use to decide where to place the boundaries between the major divisions of the geologic time scale?
Major changes that are recorded in the fossil record
Absolute Dating
Determining the actual age of an event in years.
To determine when a volcano erupted, Michael used a sample of a mineral that formed when the lava cooled and became solid rock. He measured the amount of argon-40 in the sample to find how much potassium-40 had decayed since the rock formed. What else would Michael need to know to find the age of the mineral in years?
The half-life of potassium-40
Determining whether an object or event is older or younger than other objects or events.
Relative dating
A long cylinder of ice.
Ice Core
Which of the following statements correctly defines geology?
1. It is the scientific study of the history of Earth and the processes that shape it.
2. It is the scientific study of the history of the solar system and the processes that shape it.
3. It is the scientific study of the development of life on Earth and the processes that change it.
4. It is the scientific study of the structure of Earth's atmosphere and the processes that change it.
A: It is the scientific study of the history of Earth and processes that change it.
Radioactive Decay
The breakdown of a radioactive isotope into a stable isotope of the same element.
Index fossils are used to date rock strata that would otherwise be very difficult to date. Which of these statements describes a key characteristic of index fossils?
They existed for a short span of time.
The principle that states that younger rocks lie above older rocks of the layers have not been disturbed.
Superposition
The time needed for half of a sample of a radioactive substance to undergo radioactive decay and form daughter isotopes.
Half-life
Why did geologists develop the geologic time scale?
Finding the relative age of a sample by determining the relative percentages of a radioactive parent isotope and a stable daughter isotope.
What are index fossils and how are they used to determine the absolute age of sedimentary rock>
The scientific study of the origin, history, and structure of Earth and the processes that shape it.
Geology