(STACKER) – As the fourth-largest country in the world, the United States has a vast assortment of picture-perfect natural scenery to flaunt. From the Alaskan Tundra to the Gulf of Mexico, Niagara Falls to the Hawaiian Islands, the contrasts between the 50 American states and five territories are fascinating and sometimes enigmatic.
Geological, physical, chemical, and biological phenomena have rational explanations, but some are so rare they seem to be a figment of a science fiction screenwriter’s imagination. Nonetheless, understandable or not, they do—unmistakably—indulge the senses.
From features in national parks to regional quirks, Stacker compiled a list of 20 of the strangest natural phenomena in the U.S. Anyone hoping to catch a glimpse of these phenomena must remain mindful of the risks they face in the wilderness and also of the damage they could inflict on the environment. Government and community organizations manage the grounds where many of these natural happenings occur—and are often available to guide visitors through their journey.
Death Valley’s sailing stones
Florida’s colorful swamp
Great Smoky Mountains’ lightning bugs
Horsetail Fall in Yosemite
San Diego bioluminescent shore
New York’s ice volcano
Singing sands at Great Sand Dunes National Park
Petrified lightning at Great Sand Dunes National Park
Sounds of Coqui frogs in Puerto Rico
Overwintering monarchs in California
Pennsylvania’s ringing rocks
Bioluminescent fungi in Appalachia
Mother-of-pearl clouds in Alaska
Pittsburgh’s Gravity Hill
Nebraska’s Chimney Rock