Module Overview for Instructors

Pipes, Tree Roots or Unmarked Graves? Using Ground Penetrating Radar for Forensic Geophysics

The Ground-Penetrating Radar module of IGUaNA is designed to expose students to geophysical concepts and societal applications. Students will begin to understand how geophysics is useful in urban/developed environments and what sectors use geophysical data in their work.

Module Goals

  1. Students will be able to identify common buried targets (objects) in urban environments that can be found with GPR.
  2. Students will be able to explain the basic physics of a GPR system (i.e., pulse transmission, wave propagation, reflection, two-way travel time, wave attenuation, ground properties.)
  3. Students will be able to recognize a diffraction pattern as the GPR response to a point reflector/object/feature.
  4. Students will be able to estimate ground velocity from diffraction patterns using real GPR data (collected or provided) and determine the depth of objects.
  5. Students will be able to describe the limitations of GPR including different targets that give similar-looking responses and the role of soils and geology on data quality.

Assessment: Assessment of student learning can be approached flexibly. Each unit of the module includes student handouts and exercises that can be used for formative assessments. In addition, each unit includes a set of short answer questions that can be given to students as homework, on quizzes, or on exams.

Outline

The module covers material sequentially, but the units can also often be taught as stand-alone lessons. For instructors who do not wish to use the module in its entirety, suggested pairings are included in the "Context for Use" section on each unit's page.

Unit 1: What is GPR and how is it useful?

This unit introduces ground-penetrating radar (GPR) as a way to 'see' features and structures underground without the need to excavate beforehand.

Unit 2: What does GPR data look like?

This unit explains how characteristics of the ground that causes transmitted ground-penetrating radar (GPR) waves to reflect back up toward the surface. Students then work with real GPR data to determine the depth of buried objects. These real examples illustrate the use of GPR for doing societally relevant work, including work for social justice. Read more about using GPR to locate unmarked graves below.

Unit 3: Case studies and limitations of GPR

This unit illustrates the strengths and limitations of GPR as a tool for locating and identifying buried objects. Through the case studies, it also illustrates the use of GPR for doing societally relevant work, including work for social justice. Read more about using GPR to locate unmarked graves below.

Making the Module Work

To adapt all or part of the Ground Penetrating Radar module for your classroom you may also want to read through Using IGUaNA Modules for Your Course, which includes sample pathways through portions of IGUaNA modules.

Using GPR to locate unmarked graves

One of the case studies in this module involves the use of GPR to evaluate a site for the presence of unmarked graves. Many cultures around the world bury the physical remains of the dead, and the locations of their graves are sacred places. In the U.S., failing to protect these sacred spaces is one of the countless injustices that have been committed by White people against Black and Indigenous communities. Unmarked grave sites in the U.S. include cemeteries for enslaved people, where slave holders typically made no effort to mark or protect burial sites, and cemeteries on the grounds of "Indian boarding schools" run by U.S. government agencies, where Native American students were buried without their families' knowledge or consent. Locating unmarked graves and reflecting on past harms is one small step we can take toward healing the harm that has been done through these acts of disrespect. Only by uncovering and acknowledging these injustices can we begin to address them.

There are many current efforts to locate and identify unmarked graves, and to educate the public about them. Here are a few examples:

Why use ground penetrating radar (GPR)?

One major advantage of using GPR to locate possible burial sites is that it does not require disturbing the ground in any way. A GPR survey is conducted by pushing an instrument along the ground surface, and trained geophysicists can interpret the resulting data with remarkable accuracy. The unmarked graves case study in this unit is an illustration of one of the ways that GPR, and by extension geophysics, can be used to work for justice.

Teaching about unmarked graves

For some students and instructors, the GPR case study seeking to determine whether there are unmarked graves on a particular site is more than an academic question. It may also be a reminder of historical racial trauma experienced by their families or other members of their communities. In addition, in some cultures there are powerful taboos related to burial sites; even conducting a GPR survey may be seen as an intrusion in a sacred space.

Knowing that talking about unmarked graves in class may evoke powerful emotions for some students may make some instructors reluctant to teach this particular example. However, we encourage instructors to include it, with empathy and compassion, precisely because of the potential for relevance to students. "By anchoring lessons in texts and examples that are culturally relevant to students' lived experiences, students will be able to see themselves reflected in the curriculum and draw connections to their families and communities, which sends a message that their stories are valued and worth telling" (Rush, 2021). Moreover, this is one example of how science can be a tool for justice. See the reference list, below, for more information.

References

African-American slave cemeteries

  • Where Are African-American Slaves Buried? Irma Watkins-Owens, Ph.D., associate professor of history and African American studies, is working to create a database of enslaved African Americans' burial grounds in the United States. She explains, "The burial grounds of the enslaved are sacred spaces; they mark their place in the world and are a testimony to the humanity of a people denied dignity in life. We must remember, recover and restore these spaces. Doing so is a testimony to our own humanity."
  • The Root: The Sad History Of Cemented Cemeteries: In this article, Jonathan Pourzal writes about cemeteries that are discovered by developers as they begin new building projects. "Many African cultures share the belief that a person's soul lives on after death. Therefore, a burial ground is more than a final resting place; it is a sacred space to be preserved for the use of transitioned souls."
  • When Black History in Unearthed, Who Gets to Speak for the Dead? Jill Lepore explains why it is so challenging to identify who owns slave cemeteries. "Descendants can be hard to find, for reasons that have everything to do with the atrocities of slavery, which stole people from their homes, separated children and parents, barred marriage, and assigned to people no family name except that of the people who claimed to own them."
  • For even more general context, see the New York Times' 1619 Project about the history of slavery in the U.S.

Native American boarding schools

  • U.S. Indian Boarding School History briefly describes horrific treatment suffered by tens of thousands of Native American students and reminds us that "Many children never returned home and their fates have yet to be accounted for by the U.S. government."
  • The history and culture of Indian boarding schools documents the treatment of Native American students at federally-run boarding schools. In addition to forcibly removing children from their families and homes, school authorities (White men, often trained as military leaders, not as teachers) forbade children to speak their native languages or to engage in their traditional cultural practices, including prayer. Children had their native clothing taken away from them, were given "White" names, and were forced to eat unfamiliar food. This assault on Native cultural identity carried over into the schools' curricula, as well. In addition, disease ran rampant. 
  • U.S. to Search Former Native American Schools for Children's Remains describes a new initiative that will delve into boarding school records in search of information about burial sites. 
  • American Indian Boarding Schools Haunt Many describes how the memories of Native American boarding schools continue to impact the lives of survivors and their families. 
  • Death By Civilization is a personal narrative from the daughter of a survivor of Saint Mary's Catholic Indian Boarding School on the Ojibwe reservation in Odanah, Wisconsin.