Ask your students to research how trenches form through plate tectonics. Have them write or prepare a presentation describing how two plates diverge from each other, pulling away Earth's crusts and forming deep sea trenches with depths upward of 7 miles. Give extra credit for in-depth explanations, including the mechanics of plate tectonics and the causes of plate movement.
Research land formations via the Internet or earth science books to construct appropriate questions regarding natural land formations near trenches. Teach students about how trenches usually have a high level of volcanic activity. As the plates separate, magma from underneath the lithosphere can break through the crust, forming chains of volcanoes. Ask questions regarding volcanic activity, island formation and other related topics you come across with your research.
Discuss the basic environments of trenches. Include questions regarding water temperature and water pressure. Instruct students to explain the effects of the environment on plant and animal life.
Require students to complete a craft project. For example, use poster board drawings with a trench cross-section or construct a three-dimensional trench model.
Set a date for each student to present their craft project along with a written presentation of their research. Allow students to answer all the questions you created during the project formulation process and use the trench craft as a visual aid during the presentation.