Spits on Mars

In-Class Activity_Water World

Julia Kahmann-Robinson PhD and Marjorie Chan PhD, University of Utah Department of Geology & Geophysics

Purpose

• Understand the concept of longshore drift and the geomorphic features it creates/develops.
• Search for and identify sand spits/tombolos on Mars

Preparation

1. Have an Internet connection in classroom.
2. Prepare MOLA colorized elevation maps if desired (see Exploration)

Resources

Spit Formation in the UK and longshore drift: http://www.youtube.com/watch?v=Fe9YBuK_qEo&feature=endscreen&NR=1

Engagement

Have students view the following video of Spit Formation in the UK and consider the following questions:

http://www.youtube.com/watch?v=Fe9YBuK_qEo&feature=endscreen&NR=1

1. On the beach, where would the coarsest of grain sizes be deposited (nearest the ocean or nearer the land; proximal/distal)?
2. What determines the location of particular grain sizes?
3. What governs the growth of a spit?

Exploration

Using a MOLA colorized elevation map have students do the following (students may come up to the screen and point, or students can annotate a map):

1. Mark or point to areas on Mars where spits could be present.
2. How did they make their decisions? [Answers can range from finding an area with and open basin, cuspate like features or peninsulas that jet out from the dominant "shoreline" morphology etc.]
3. If longshore drift were present in your chosen regions, what direction is the longshore drift heading?[answers vary]

Explanation

Longshore drift- <a></a>caused by wave and current action. It is the primary method of sediment transport along the beach. The direction of this motion is always parallel to the beach face.

Elaboration

1. What do deposits of longshore drift look like in cross-section? [encourage graded bedding and/or swash zone sedimentary structures such as planar cross beds etc.] *Have students hypothesize or perhaps draw a stratigraphic section of sorts and guide them
2. What determines the size of grains that are deposited?[High energy can deposit larger grains and low energy smaller grains]

Evaluation

View the following Mars image online of Cape Verde at Victoria Crater on Mars: http://www.nasaimages.org/luna/servlet/view/search/where/Cape+Verde?q=+mars+rover&os=0&pgs=50&sort=Title%252CDate

• Ask students to point out high energy rocks [cross-beds, cliff-forming] and low energy rocks [finer-grained slope forming material]
• While this is not the right depositional environment, the image does illustrate varying energy environments of deposition.