Relative Dating
The process of determining whether an object or event is older or younger than other objects or events.
What is relative dating?
The principle that the same geological processes that operate today also operated in the past.
What does uniformitarianism mean?
A gap in the geologic record where rock layers have been eroded or not deposited.
What is an unconformity?
A timeline that organizes Earth's history into different periods and epochs.
What is the geologic time scale?
A fossil that is used to determine the age of rock layers because it was widespread but existed for a short period.
What is an index fossil?
In undisturbed layers of rock, the oldest layers are at the bottom and the youngest are at the top.
What does the principle of superposition state?
An example of a process that supports uniformitarianism.
What is erosion or sedimentation.
Three main types of unconformities.
What are angular unconformity, disconformity, and nonconformity?
Eons.
What are the largest divisions of geologic time called?
One example of an index fossil.
What are trilobites? brachiopods?crinoids? ammonites?
Fossils and rock
How can fossils help in relative dating?
It helps scientists understand Earth's history by using processes we can observe today.
Why is uniformitarianism important in geology?
It shows that rock layers were tilted or folded before newer layers were deposited on top.
What does an angular unconformity tell us?
Holocene.
What is the current epoch we are living in?
They help correlate (match) the ages of rock layers in different locations.
Why are index fossils useful for geologists?
Layers of sediment are originally deposited horizontally under the action of gravity.
What is the Law of Original Horizontality?
James Hutton.
Who is credited with the idea of uniformitarianism?
Rock uplifted, eroded, and sedimentary rock deposited on igneous or metamorphic rock
What is a nonconformity?
Eons, eras, periods, and epochs based on significant events in Earth's history.
How is the geologic time scale divided?
By identifying the presence of specific index fossils, geologists can estimate the age of the rock layers.
How do geologists use index fossils to date rock layers?
Sediment deposited in large continuous sheets to help date rock.
What is a lateral continuity?
Earth's features developed gradually over long periods, allowing for an understanding of Earth's AGE.
How does uniformitarianism relate to geological time?
They indicate missing time periods that can affect the interpretation of the geological history.
Why are unconformities significant in relative dating?
The Cambrian Explosion, when a wide variety of life forms first appeared.
What major event marks the beginning of the Paleozoic Era?
It should be widely distributed, have a short geological lifespan, and abundant.
What characteristics make a good index fossil?