Solve me a river

"Unexplainable or Not" is a game show podcast where host Noam Hassenfeld, along with co-host Bird Pinkerton and science reporter Neel Dhanesha, present three science mysteries related to rivers to guest Sally Helm. Sally must guess which mystery has been recently solved. The mysteries include the cause of freshwater mussel die-offs, the reasons behind dramatic river course changes (avulsions), and the determination of the world's longest river. Ultimately, Sally guesses incorrectly, and the hosts reveal that scientists have recently discovered the combined factors of super elevation and gradient advantage that cause rivers to change course, using space lasers to measure and map river surfaces. The episode concludes with a song about the revealed mystery and reflections on the podcast's cover art, which depicts the historical courses of the Mississippi River.