How geologic beds and other planar features interact with topography: Rule of V's

Alyssa Abbey
California State University-Long Beach,

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Initial Publication Date: May 21, 2026
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Summary

This activity helps students learn about how planar features, such as faults and bedding contacts interact with topography. Students explore various topographic map patterns, then focus on how bedding contacts appear in a valley if the beds dip at various angles (horizontal, vertical, upstream, downstream). The activity aims to help students discover and develop the rule of V's for themselves. Students experiment with different bedding orientations (horizontal, vertical, dipping upstream, dipping downstream, steeply dipping and shallowly dipping). Students begin to develop intuition about which way the V shape will point relative to the topography, and how broad/narrow the V shape will be based on the dip angle. They should be able to create the rule of V's on their own by the end of the activity.

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Learning Goals

Students will:

  1. Practice using the Visible Geology web-based application to visualize geologic relationships in 3D
  2. Test how differently dipping geologic beds are expressed on the surface of a specific landscape (i.e., valley)
  3. Construct a list of rules for how planar features with different dips and dip orientations appear in in map view in a valley (i.e., the rule of V's)

Context for Use

This activity is used for a review at the beginning of a structural geology course at California State University Long Beach (CSULB). The class is taken mostly by seniors and a few juniors majoring in Geology and/or Earth Systems. It has also been used to introduce students to the rule of V's in the Introduction to field methods class at CSULB (sophomores and juniors).

Students do not need to have heard of the rule of V's, but it helps to have activities prior to this that involve reflecting on how different topographic surfaces expose geologic beds differently (e.g., discussions/activities about apparent thickness, differential erosion).

This activity is scaffolded with a pre-lab or homework for students to become familiar with the Geology Explorer module in Visible Geology.

Description and Teaching Materials

Begin with a review of the homework/pre-lab to make sure students can use the Geologic Explorer module effectively.

Students use a computer and the Visible Geology web-based application to open a project with provided topography (pre-created valley that is more dramatic and has a more obvious upstream direction), add various layers, then tilt those layers with different dip angles, recording their observations and annotating screenshots of their experiments.

Depending on student familiarity with the program and how much extra experimenting they may want to do, the activity should take ~2 hours.
Attachments (supporting materials) include the Pre-lab/homework assignment, the Visible Geology activity, an example of student work of the completed activity, the optional block model activity (see teaching notes), and the optional augmented reality sandbox model activity (see teaching notes).

Visible Geology teaching activity_pre-labhomework_ruleof_vs.docx (Microsoft Word 2007 (.docx) 5.1MB May15 26)

Visible Geology Teaching Activity - Pre-lab Homework for Rule of V_s.pdf (Acrobat (PDF) 397kB May15 26)

Visible Geology teaching activity_rule_vs.docx (Microsoft Word 2007 (.docx) 4.4MB May15 26)

Visible Geology Teaching Activity - Rule of V_s.pdf (Acrobat (PDF) 636kB May15 26)

Optional block model activity (PowerPoint 2007 (.pptx) 2MB Mar10 26)

Optional Sandbox activity (Microsoft Word 2007 (.docx) 368kB Mar10 26)

RuleofV_Example_studentwork.docx (Microsoft Word 2007 (.docx) 4.5MB May1 26)

Teaching Notes and Tips

  • To save and share their work in Visible Geology, students are encouraged to log in with their Google Account.
  • Students must log in with their Google account to access the provided "project" that includes the valley topography.
  • I like to do an introductory activity in the week leading up to this with block models we have made of porcelain (could be wood or even digital). The two block models I use show how horizontal beds are exposed on the surface where there is differential erosion and a small carved canyon. They see that the map pattern mimics the topography. The second block model has vertical beds, horizontal beds, beds dipping downstream and an intrusion. They see that the different angles control the surface exposure, including v's pointing downstream when beds dip downstream, and that vertical beds make straight line contacts with no "V" shape.
  • My lab periods are 3-hours long, so I also include an augmented reality sandbox projection activity (e.g., the one shown in this video). Students take planes (cardboard) and slide them into the sand at different places in the topographic display and where the sand intersects the cardboard a V shape forms. This is the line they draw on their topographic map as if they were drawing a contact.

Assessment

The lab activity includes reflection questions and required screenshots of student experiments. These are graded on a point scale (noted for each question on the activity).

References and Resources