A hydrothermal explosion Tuesday morning in Yellowstone National Park sent boiling water, steam and rocks high into the sky which then rained down on tourists that were along the Biscuit Basin Trail. The explosion was caught on video by Vlada March as she and her family were on the boardwalk near the Black Diamond Pool. March said her mother was hit by debris, but unharmed. The National Park Service said no injuries were reported. The explosion damaged the Biscuit Basin boardwalk forcing park rangers to close it and the Biscuit Basin parking lot. Rangers said they did not know when the boardwalk may reopen. The U.S. Geological Survey said hydrothermal explosions are relatively common at Yellowstone. They said there was another explosion in the Biscuit Basin area in May of 2009. Hydrothermal explosions happen when water suddenly flashes to steam underground, the USGS said. The National Park Service said Tuesday's explosion does not reflect a change in Yellowstone's volcanic system. The park's data monitors showed volcanic activity remained at normal levels. Black Diamond Pool is just over two miles north Old Faithful. Yellowstone officials said Grand Loop road remains open. Video source: CNN Read more: https://www.9news.com/article/tech/science/biscuit-basin-yellowstone-explosion/73-6f71e61a-eead-41f8-9814-f37a359ddd96 More local videos here: https://bit.ly/2Pa0d1l Subscribe to NEXT: http://bit.ly/2eP1GwI Stay connected: 9NEWS Website: http://www.9news.com/ Facebook: https://www.facebook.com/ilike9news Twitter: https://twitter.com/9NEWS Instagram: https://www.instagram.com/9newsdenver/ Download the 9NEWS App: https://www.9news.com/appredirect/ Sign up for the 9NEWSLETTER: https://www.9news.com/email 9NEWS (KUSA) is located in Denver, Colorado.