Science and Teaching for Field Instructors

The Case of the Disappearing Log

Case of the Disappearing Log offers learners an opportunity to investigate logs, trees, forests, and ecosystems through a lens of cause and effect and decomposition. In this activity, learners assume the role of “detectives” faced with a nature mystery. First, learners explore a decomposing log and look for evidence of how the log is changing. They make possible explanations for what might be causing the log to disappear. Learners then learn about organisms and forces that decompose wood and the signature evidence that is left behind. Learners use a Disappearing Log Key to identify which organisms might have left behind which evidence and use this information to make explanations about what has happened to the log since it was a tree. Finally, the instructor offers the idea that the log isn’t really disappearing but is actually turning into the invisible gases that are part of the cycling of matter in all ecosystems.

Learners will:
  • Explore fallen logs and find evidence for how they are changing.
  • Work together with peers in pairs and small groups.
  • Use cause and effect as a thinking tool to engage in discussion and meaning-making.
  • Learn information about log decomposers from Cause and Evidence Cards.
  • Use a key to identify evidence of different organisms and other impacts on logs.
  • Use observation and reasoning to make explanations about what has happened to the log, including a possible sequence of events.
Download Full Instructor Guide:
case2021
Watch Activity

Note: This video was edited to focus on how the instructor leads the activity; the actual activity is much more student-focused, and students spend most of the activity exploring and discussing ideas with their peers. We revised this activity in 2021, well after the making of this video. Please follow the written student activity in the case of discrepancies.