Teach the Earth > Rates and Time > Teaching Activities > Depositional Environments and Geologic History Labs

Geologic History Lab Pair

Maria Waller and Kathleen Gilbert
Geosciences Department, Wellesley College

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This page first made public: Feb 17, 2012


This is a pair of labs that incrementally prepare students to interpret the geologic history of a rock sequence. The first lab introduces students to depositional environments and fossils. The second lab presents a sequence of rocks from Bryce, Zion and the Grand Canyons. During the two labs, students learn first to interpret depositional environments from sedimentary rocks and then apply this to interpreting the changing environments through time in order to create a geologic history for this area of the American southwest.

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These two labs are part of an introductory geology course for both majors and non-majors. The class includes students ranging from first-years to seniors.

Skills and concepts that students must have mastered

  • Ability to describe and identify rocks
  • Ability to describe and identify rocks
  • Ability to describe and identify small group of fossils using id. charts
  • Familiarity with depositional environments and their characteristics
  • Familiarity with depositional environmental indicators

How the activity is situated in the course

These two labs immediately follow our rock identification labs as one way to show students how to apply their rock identification skills and how rocks are used as tools to interpret the earth's history.


Content/concepts goals for this activity

  • Learn to recognize environmental indicators in sedimentary rocks
  • Learn to describe and identify a small number of fossils
  • Learn several different depositional environments and their characteristics
  • Recognize the spatial relationships between different depositional environments
  • Learn to sequence rocks in order of relative age (principle of superposition, cross-cutting relationships)
  • Learn concept of transgressions and regressions
  • Learn that unconformities represent erosional surfaces
  • Learn to recount a geologic history from a sequence of rock

Higher order thinking skills goals for this activity

  • Learn to relate the textural/color/etc. features in a sedimentary rock to the characteristics of depositional environments to understand what determines which sediments are deposited in which environment
  • Learn to use the presence or absence of particular fossils to aid in the determination of the depositional environment
  • Learn to attribute change to something (cause and effect)

Other skills goals for this activity

  • Develop observation and description skills
  • Begin the process of coalescing various forms of data to make interpretations
  • Make interpretations with larger amounts of data
  • Practice clear, complete essay writing

Description of the activity/assignment

The goal of this pair of labs is for the students to learn to apply rock and fossil identification skills to determining rock formations, sedimentary depositional environments, age ranges, and, ultimately, to writing a geologic history of a sequence of rocks from Bryce, Zion, and Grand Canyons. During the first of the two labs, the students learn to make fossil and sedimentary structures identifications. They add these skills to their rock and mineral identification skills to make interpretations of the sedimentary environments along a generalized profile from terrestrial to offshore locations. During the second lab, they apply these skills to a sequence of rocks from the southwestern U.S. to interpret the environmental changes that have occurred over time. They also begin to learn how to use fossils to determine age ranges for these changing events. Once they put together all of their data, they construct a stratigraphic column and piece together a written narrative of the geologic history of the area. The students work in groups to collect their data and determine their stratigraphy. They write their geologic histories individually. The students learn how to apply their skills and knowledge to make interpretations and also learn how to support their determinations with data.

Determining whether students have met the goals

For the Depositional Environment lab, students complete a diagram that includes recording their rock, fossil, and sedimentary structure identifications. Students also answer some questions to summarize what they have learned.

For the Geologic History lab, we ask students to write an essay presenting the geologic history of Bryce, Zion and Grand Canyons.

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