Horseshoe Lake, California
Horseshoe Lake enjoys a stunning location, its waters shimmering in the Californian sun, with swaying trees and mountains all around. Yet first impressions can be deceptive.
Set high in the hills, in Lassen Volcanic National Park, not far from the Mammoth Mountain Ski Resort, this is a place fraught with danger — where swimming is permitted, but best avoided.
The problem here is gas — carbon dioxide, in particular. Issues first arose in 1989 and 1990, when a series of small earthquakes in the region opened cracks and crevices that allowed dangerous gases from the bubbling magma below to rise to the surface. The result? Polluted soil — and more than 100 acres of dead plants and trees.
These days, nothing grows in the affected areas and, with gases and toxins from the banks leaching into the lake, the dangers here endure. Thinking about paying a visit? Be sure to look out for signs, and always heed warnings.