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Sat April 20, 2024 Oracle, AZ 85623 US Directions
Wanna' celebrate Earth Day? Get ready for a fun adventure that combines fitness, science, and beautiful scenery at the Biosphere 2
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TMC Earth Day 5k Run/Walk

$40 8:30AM MST - 11:00AM MST
17 spots left. Registration ends April 18, 2024 at 11:59am MST

Children's 5k

$5 8:30AM MST - 11:00AM MST
14 spots left. Registration ends April 18, 2024 at 11:59am MST
Open to ages 1 - 14.

Event Website

Additional event information can be found at


32540 S. Biosphere Road
Oracle, AZ US 85623


April 15 Update: Click here for the pre-race email that has been sent to all participants, with details on the schedule, the course, driving directions, awards, and more.  


We're out of guaranteed shirts for new registrants: Even though we've ordered additional shirts, as of April 15th, we've hit our shirt limit.  Thus, all registrations after April 15th will be asked to pick up a souvenir shirt AFTER the race, at the race site starting at about 10:00 am at the Run Tucson tent.


All online registration will close at noon on April 18th.  In-Person Registration will continue at these three times and locations:

* Thursday, April 18 4:00 - 6:00 pm  at The Running Shop, 3055 North Campbell, Tucson.  Packet pickup and in-person registration.

* Friday, April 19 4:00 - 6:00 pm at The Running Shop, 3055 North Campbell, Tucson.  Packet pickup and in-person registration.

* Saturday, April 20 7:30 - 8:15 am at Biosphere 2, 32540 S Biosphere Rd, Oracle, AZ 85739. Race day registration and packet pick up in the parking lot by the front entrance at the Biosphere 2. 


Looking for a way to celebrate Earth Day? Join us at Biosphere 2 for a 5k run and walk, entirely on the grounds of the famed facility. 

Whether you're a seasoned athlete or just looking for a fun way to get some exercise, you're sure to enjoy yourself at the world-famous Biosphere 2.  


Clear your schedule and join us at the April 20th TMC Earth Day 5k, where you can walk or run the hidden Biosphere 2 backroads, nestled at the base of the majestic Catalina Mountains, north of Tucson. The rolling 3.1 mile course is perfect for racing and walking, with gorgeous desert and mountain views and a start and finish on the beautiful Great Lawn.  
After the 5k, you can relax, listen to live music, snag some food, and enjoy other fun activities, so make sure to stick around to socialize and have some fun. All registrants receive free entry to the Biosphere 2 informative tour of the renowned research facility, with an exclusive peek into the inner workings of the Biosphere 2, a wild world of wetlands, rainforests, grasslands, fog deserts, and the big blue ocean. It's like a backstage pass to nature's superstar habitats!
The TMC Earth Day 5k is raising funds for the Ocean Reef research project, learning how to grow ocean reefs in a changing climate.  See details and donate here. 
We've raised the limit, so now capped at 750 Registrants (158 slots available as of April 2)
  • 600 special sublimated souvenir shirt + another 150 cotton shirts -- pick your style and size, first-come first-served at packet pickup
  • Timed 5k with finisher's video
  • Age group and overall awards courtesy of The Running Shop
  • Free entry to the world-famous Biosphere 2
  • Snacks and drinks
  • Food trucks with yummy post-race food for purchase
  • Children's activities
  • COX Conserves special festivities planned

Click here for the Damion Alexander photos.  Click here for the video Damion put together. Click here for the KGUN Morning Blend pre-race interview about the TMC Earth Day 5k at the Biosphere 2.

Don't miss this chance to visit the earth's entire ecosystem under one roof while celebrating Earth Day.

Bring the Kids! Strollers are allowed at this child-friendly event, with a free Kid's Dash & Kid's Zone.  Special $5 price for children 14-and-under: includes race number, timing, and entry to Biosphere 2, but no t-shirt.

Do Good! This inaugural event raises funds for the world-renowned Biosphere 2's Ocean Reef Lab. 

Terrain: mostly pavement, with a brief dirt section

Difficulty: hilly in sections

Weather: 50's - 70's

Differently Abled: Yes, be mindful of hills and dirt road

Pets Allowed: No

Want Training Advice? Contact RRCA-certified running coach Tia Accetta at 

Planned 2024 Schedule:

7:15-8:15 am Race day registration and packet pick up
8:30 Start time for TMC Earth Day 5k Run/Walk
9:30 Free Kids Dash
9:45 or so: Awards
Ongoing: All registrants can visit Biosphere 2 on their own -- no need for a formal tour!

All non-running guests can purchase Biosphere 2 admission for the discounted rate of $10 (before 8:30 am) and all children under 12 are free.

This event is a partnership between Run Tucson & the Biosphere 2, the University of Arizona

Questions? Contact Race Director Randy Accetta at  

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