Cordilleran Section - 115th Annual Meeting - 2019

Paper No. 35-1
Presentation Time: 8:00 AM


FAUST, Megan Thackeray Scott, Geology, Portland Community College, Portland, OR 97217

Caldera forming eruptions can be modeled using materials on-hand as a way to engage introductory geology students in a laboratory activity. The activity described herein is suitable for use in any introductory geoscience course that discusses volcanic landforms and/or volcanic processes. The materials needed for this activity include large plastic containers, a variety of sediments, balloons of different shapes and sizes, and bamboo skewers. The basic premise of the model is to bury a balloon under sediment in one of the containers, and stick the skewer through the sediment to pierce the balloon. This models a volcanic eruption, where the balloon represents a deflating magma chamber emptying its contents, with the overlying material subsiding to create a caldera. After participating in the caldera modeling activity students perform higher on assessments when asked about caldera landforms and the associated volcanic processes.

A valuable component of the caldera modeling activity is the opportunity for students to design their own experiment. Many students in introductory geoscience courses are enrolled in the course to fulfill a general science requirement, so it is especially important for students to have exposure to experimental design. In preparation for this lab, an in-class discussion about calderas is recommended. The discussion enables students to pose more meaningful and specific inquiries that they can attempt to answer in the activity. Examples of concepts students might consider when designing an experiment include: How does the depth of the magma chamber affect the shape/size of the caldera? Does the type of sediment impact the outcome? What impact would a more complex magmatic system (made of a twisted circus balloon) have on a caldera? What if the magma chamber erupted from multiple vents simultaneously? Students are instructed to consider which measurable variable(s) they will vary between trials and how they plan to measure the outcomes of each trial. At the conclusion of the experiment, the student is asked to analyze and summarize the results of their experiment pertaining to caldera formation processes, as well as to reflect on the choices they made in their experimental design. This activity is a beneficial curriculum component and it fulfills course outcomes for introductory geoscience courses.