Introductory-level undergraduate earth science class, although talking points could be adapted for younger students by giving more background.

Students should understand that divergent boundaries occur where plates are moving apart and new crust is being created. Students should also be familiar with elements of the visualization (introduced in Visualization 1; i.e. how earthquakes are represented, what different sizes and colors of points represent) and have mastered the concepts associated with Visualization 1.

This activity is part of a series of visualizations in a unit about plate tectonics, although each visualization could also be used in isolation.

Students will understand the following concepts:

• Shallow, low-magnitude earthquakes commonly occur at divergent plate boundaries.
• Earthquakes at divergent plate boundaries are distributed with predictable locations and depths.
• Earthquakes at divergent plate boundaries occur as new crust is created and other crust is pushed apart. This causes the crust to crack and form faults where earthquakes occur.
• Most earthquakes at divergent plate boundaries occur at mid-ocean ridges where two pieces of oceanic crust are moving away from each other. Some earthquakes at divergent boundaries occur in the middle of continents in rift zones.

Students will be able to:

• Synthesize large data sets to recognize naturally occurring patterns
• Use patterns in data sets to make predictions about the distribution and characteristics of earthquakes
• Visualize data in 3D that is traditionally represented in 2D

The purpose of this activity is to introduce students to the distribution and characteristics of earthquakes associated with divergent plate boundaries. Students will learn about how the magnitude and distribution of earthquakes at divergent boundaries are related to processes that occur at these boundaries and to the geometry and position of the two diverging plates. Because the depth of earthquakes can be difficult for students to visualize in 2D representations, this activity allows students to visualize the 3D distribution of earthquakes within Earth's surface, which is essential for understanding how different types of earthquakes occur in different tectonic settings. Locations featured in the visualization include the Mid-Atlantic Ridge, the East Pacific Rise, and the East African Rift Zone. Talking points and questions are included to facilitate using this visualization as part of an interactive lecture. In addition to playing back the visualization, instructors can also download the visualization software and data set and explore it themselves.

'Quakes Questions' throughout each activity are short-answer questions that students answer while the visualization is playing to ensure that they are taking away key concepts. These questions require students to synthesize ideas and articulate their understanding of concepts introduced in the visualization. The final 'Quakes Question' requires them to integrate concepts from this visualization with those from 'Visualization 2: Earthquakes and Convergent Plate Boundaries.'

The visualization software used to create this visualization is freely available and can be downloaded from http://keckcaves.org/education/. In addition to playing back the visualizations available here, instructors can also download the visualization software and data sets and explore it themselves. Download the software and quick-start guide to begin exploring your own data sets in your classroom.

Please contact the author (clharwood@ucdavis.edu) if you would like a higher resolution video.