DISPELLING MIDDLE SCHOOL MISCONCEPTIONS OF GRAND CANYON FORMATION THROUGH HANDS-ON ACTIVITIES

Teaching earth science in middle school is made difficult by misconceptions that the students bring into the classroom, particularly given the limited opportunity to conduct field exercises. To address misconceptions about absolute and relative geologic time and the formation and erosion of rocks, we developed a unit that combines hands-on activities to teach geoscience concepts with practical application using visuals from the Grand Canyon. Students have many pre-existing misconceptions about the Grand Canyon, such as believing the Colorado River formed the exposed rocks over a period of tens to hundreds of years. Our unit’s goal is for students to demonstrate a basic understanding of five main ideas: 1) Rocks formed prior to the erosion of the Grand Canyon; 2) Rocks form from sediments that are originally deposited in horizontal layers with oldest rocks on the bottom; 3) Rivers are major erosion agents but not all rivers form canyons; 4) The formation and erosion of rocks occur in thousands to millions of years; and 5) Plate tectonics play an important role in the formation of the Grand Canyon. We begin with an activity to determine what students know about geologic time, the formation of rocks and relative dating. Students are shown a fossiliferous limestone and basalt that represent rocks found at the Grand Canyon. They are asked to write down which rock they think is older, how they know, how old in years they think the rock is, and what additional information they think would be helpful for deciding. Next, students participate in activities developed for each main idea that will also help them to answer whether the limestone or basalt is older in the Grand Canyon. Follow-up activities include exploring rivers as erosion agents using a stream table set at various slopes, shaking a combination of water, sand, rocks and clay particles in a jar to understand horizontal layering, applying relative dating knowledge by taking core samples of playdough layers, and making a scale model of geologic time from the formation of the Earth to the present. The unit is interspersed with pictures from the Grand Canyon where students are asked to answer questions based on what they learned from the activities. At the end of the unit, students are able to describe the formation of the Grand Canyon and show that they comprehend each of the main ideas.