1.
Where is the Great Unconformity best displayed, and in what ways is it
significant to our interpretation of Earth's history?
The Great Unconformity is best displayed in the Grand Canyon. Its significance lies in the vital
insight it gives us into the formation of its rock layers. It allows us to determine the time that
passed between each layer’s formation. This information is crucial to the concept of deep
geological time and can act as a reference for other rock formations.
2.
Refer to the stratigraphic column:
What types of unconformities are represented by the Great
Unconformity? (Provide specific rock layers)
The Tonto Group and Layered Paleozoic Rocks display an angular
unconformity with the Vishnu Basement Rocks.
3.
Using the stratigraphic column of the Grand Canyon provided; identify
two other unconformities within the Precambrian (i.e. formations below
the Great Unconformity). You must name the unconformities and
support your answer with the amount of time missing (show your
calculation).
Two other unconformities within the Precambrian are the Great Unconformity and the
Angular Unconformity above the Vishnu Schist. The amount of time missing can be calculated
by subtracting the age of the younger formation from the age of the older formation. The
amount of time missing between the Grand Canyon Supergroup and the Vishnu Basement
Rocks is 1.8 billion years – 770 million years = 1.03 billion years.
