TMC Earth Day 5K
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TMC Earth Day 5K at Biosphere 2
The TMC Earth Day 5K at Biosphere 2 takes place on April 18, 2026 at Biosphere 2 in Oracle, AZ (32540 S. Biosphere Road, 85623). The event includes the TMC Earth Day 5k Run/Walk and a Children's 5k.
The course is a rolling 3.1 mile route entirely on the grounds of Biosphere 2, with a start and finish on the Great Lawn. Runners and walkers pass desert backroads with views of the Catalina Mountains. Terrain is mostly pavement with a brief dirt section and has hilly segments; participants with mobility considerations should note the hills and dirt road.
Event features include timed 5k results and a finisher's video, age group and overall awards, and souvenir shirts for the first 600 registrants. All registrants receive free entry to Biosphere 2 and access to its exhibits, including wetlands, rainforests, grasslands, fog desert areas, and ocean displays.
Post-race activities listed for the day include music, food trucks, snacks and drinks, a Kid's Dash and a Kid's Zone. Practical notes: organizers request parking in the main Biosphere 2 lot and following on-site staff directions. Strollers are allowed; pets are not permitted. The event raises funds for the Biosphere 2 Ocean Reef research project. Visit the organization's website for the most recent information.
