Now, peering into a newborn crater, they felt the ground tremble ... and plug dome—can be found in Lassen Volcanic National Park, where they literally bubble and steam.

Under a swath of Kentucky hills and hollows is a limestone labyrinth that became the heartland of a national park. The surface of Mammoth Cave National Park encompasses about 80 square miles.

Vermont-based astrophotographer Michele Hernandez Bayliss has captured stunning views of Messier 94 - also known as the ...