# Erosion of the Grand Canyon

Carol Ormand
,
SERC, Carleton College
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#### Summary

Students estimate the volume of the Grand Canyon to calculate the average rate of erosion of the canyon, assuming the canyon began to form approximately 6 million years ago. They then find out how much sediment the Colorado River is actually carrying, in cubic feet per year, and compare that to their calculated value.

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## Context

#### Audience

Geology of the National Parks (intro level course for majors and non-majors)

See the course description, including links to all of the other teaching activities for this course.

#### Skills and concepts that students must have mastered

Multiplication, division, and unit conversions

#### How the activity is situated in the course

This is the second of two labs about Grand Canyon National Park. It follows a lab about the geology of the Grand Canyon and precedes a field trip to a local river gorge.

## Goals

#### Content/concepts goals for this activity

Students will begin to grasp how the Colorado River could carve the Grand Canyon

#### Higher order thinking skills goals for this activity

Creative problem solving - I ask students to come up with several different methods to estimate the volume of the Grand Canyon

#### Other skills goals for this activity

Students will strengthen their quantitative thinking skills through practice

## Description of the activity/assignment

Students estimate the volume of the Grand Canyon to calculate the average rate of erosion of the canyon, assuming the canyon began to form approximately 6 million years ago. They then find out how much sediment the Colorado River is actually carrying, in cubic feet per year, and compare that to their calculated value. In the process of calculating the rate of erosion, they face multiple unit conversions. I also challenge them to convert their answer into units they can visualize, such as Olympic swimming pools of sediment per day.

## Determining whether students have met the goals

Working in groups, students calculate the average rate of erosion (amount of sediment per year, and amount of sediment per day) for the canyon and compare their answers to how much sediment the Colorado River is actually carrying, in cubic feet per year. They turn in a brief report, which I grade with a rubric.