Lab #_____: Sequence of Events
Introduction: Since actual rock layers can only be truly observed in nature and can not be
observed in the classroom it is necessary to create visual examples of rock layers and the
geologic events they may experience over extensive periods of time. The geologist works to
develop a model of the Earth’s history and attempts to put events in order for what happened
first, second, and do on. When the relative age of a rock or event is determined, this
information can b diagramed as a cross-section showing the vertical distribution of geologic
rock units. This lab DOES NOT consider the actual or absolute age that an event occurred or the
rock was formed.
Objective: Using cross-sections you will infer a logical sequence of geologic evetns and establish
a probably relative age for a series of rock layers.
Vocabulary:
Relative age
Fault
Unconformity
Law of
Superposition
Igneous Intrusion Igneous
Extrusion
Procedures:
Erosional surface
Law of Original
Horizantality
Weathering
Subsidence
Law of CrossCutting
Deposition
Uplift
Contact
Metamorphism
1. Using your Earth Science Reference Tables Label each rock layer on the next page with
their correct rock type based on its map symbol. (Label the igneous rock ‘igneous’)
2. Color each layer and cut them apart.
3. Follow the directions that are read to you in order to create your out crop.
4. Once completed, use your outcrop to list the steps that would normally occur in nature
to create this specific column of rock.
Conclusion:
Explain how the Laws of Superposition, Original Horizantality, and Cross Cutting are
evidenced in this lab?
Questions:
1. Describe how the Principle of Superposition was used in determining the relative ages of
the cross-sections.
2. In a cross-section suppose you find older rock layers on top of younger layers. Explain a
probable cause for this exception to the Principle of Superposition.
3. Why is an igneous intrusion younger than the rocks in which it is found?
4. Explain why the age of a fault is younger than the rocks in which it is found?
5. What is contact metamorphism?
6. How can you differentiate an igneous intrusion from an igneous extrusion in an
outcrop?
7. Why is an igneous intrusion younger than the rocks in which it is found?
8.
(1)___________________________________________________________________________________________
(2)___________________________________________________________________________________________
(3)___________________________________________________________________________________________
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Color
RED