Every summer since 1983, scientists at Crater Lake National Park have gathered data about the lake’s famous clarity. This past summer, Quanta contributing writer Rachel Nuwer journeyed with them as they conducted their annual tests. On this week’s episode, Nuwer and host Samir Patel discuss what gives the lake its vivid blue color, and what its data can tell us about the way water moves through a deep temperate lake.

Each week on The Quanta Podcast, Quanta Magazine editor in chief Samir Patel speaks with the people behind the award-winning publication to navigate through some of the most important and mind-expanding questions in science and math.

Audio coda recorded at Crater Lake National Park in July 2010 by the National Park Service Natural Sounds Program.