TMC Earth Day 5K
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Event overview
The TMC Earth Day 5K at Biosphere 2 is scheduled for April 18, 2026 in Oracle, Arizona, on the grounds of Biosphere 2. The event includes a timed 5k run/walk and a separate children's 5k for ages 1 to 14. The race raises funds for the Ocean Reef research project. Registrants receive free entry to Biosphere 2 and the first 600 registrants are eligible for a souvenir shirt. The event is presented by Run Tucson in partnership with Biosphere 2 and the University of Arizona.
Race and site details
- 5 km - TMC Earth Day 5k Run/Walk
- 5 km - Children's 5k (ages 1-14)
The course is a rolling 3.1 mile route on Biosphere 2 property, with mostly pavement and a short dirt section. The start and finish are located on the Great Lawn. The event offers timing with a finisher's video, age-group and overall awards, snacks and drinks, food trucks for purchase, and children's activities including a free Kids Dash and Kid's Zone. Strollers are allowed. The course has hilly sections and participants should note there is a brief dirt road; pets are not allowed. Remaining shirts after the event are available for pickup at The Running Shop during a stated post-race period. Visit the organization's website for the most recent information.
