Using Lava Flows & Volcanic Structures on Mars to Introduce the Concept of Relative Dating in Introductory Courses

Audeliz Matias
Skidmore College


To compare bodies of rocks in the same region and determine the sequence of events that led to the formation of these rocks, geologists use a few simple rules of observation to help determine the relative ages of the rocks. In order to do this, geologists depend on two-dimensional, vertical diagrams called cross sections. Before teaching the students to interpret these diagrams, this exercise uses THEMIS images to practice understanding relative dating in one-dimension.

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Introductory Geology Class

Skills and concepts that students must have mastered

Students should understand:
  • Topographic maps & profiles
  • The rock cycle
  • Volcanism
  • Sedimentary processes (erosion, transportation, deposition)

How the activity is situated in the course


Content/concepts goals for this activity

This activity will help students to visualize the existing rock sequence into distinctive units that can be associated with geologic process and specific events by using images containing lava flows.

Higher order thinking skills goals for this activity

This activity will enable students:
  • To develop the skills necessary to engage in relative dating and interpretation of the geologic history of an area here on Earth and other planetary bodies
  • To develop the skills necessary to solve complex problems in a deliberate and systematic manner, so they can make the transition to interpreting geologic history from geologic cross sections

Other skills goals for this activity

Other skills developed in this activity include
  • Working in groups
  • Exposing students to geologic mapping techniques used in planetary geology

Description of the activity/assignment

Geology is historical. The rocks at any one place are rarely if ever the same age. Interpreting Earth's history is a two-step process: first, interpreting each individual rock, and second, interpreting the sequence of deformational events through which the rocks have formed. Doing this requires that the students apply all the skills and knowledge they have learned about rocks and geologic process by integrating them with new skills. A student's initial challenge in interpreting cross-sections and determining the relative ages of rocks is to visualize the existing rock sequence into distinctive units that can be associated with geologic process and specific events. Thus, this exercise focus on guiding the students to observe important, basic concepts used in relative dating on a one-dimensional setting by using images from the Thermal Emission Imaging System (THEMIS) onboard the Mars Odyssey mission.

Determining whether students have met the goals

Assessment could include
  • Open discussion during class/lab about each team's results
  • A follow up cross section assignment

More information about assessment tools and techniques.

Teaching materials and tips

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