Images

A speleothem known as a "whale's tail." The fan shape comes from the calcium-carbonate-bearing water being forced through small openings and leaving the calcium carbonate behind in the distinctive fan shape.

A vertical shaft within the cave that shows how faulting and fractures in the rock create openings for air and water to weather and ultimately create a cave.

A panorama of speleothems, or cave formations, in the Caverns of Sonora.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the border of Texas and Mexico. This view is of the cliffs of Diablo East.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the border of Texas and Mexico. This view is of the cliffs of Diablo East.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the border of Texas and Mexico.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the border of Texas and Mexico. This view is of the cliffs of Diablo East.

The Caverns of Sonora have numerous types of speleothems, or cave formations. In this image, stalactites can be seen hanging from the ceiling; stalagmites can be seen rising from the floor; and all along the walls are small formations known as "cave popcorn." The central focus of the image are several columns, which occur when stalactites and stalagmites fuse.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the Texas and Mexico border. It is fed by the Rio Grande, Devils River, and the Pecos River, among others.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the Texas and Mexico border. It is fed by the Rio Grande, Devils River, and the Pecos River, among others.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the Texas and Mexico border. It is fed by the Rio Grande, Devils River, and the Pecos River, among others.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the Texas and Mexico border. It is fed by the Rio Grande, Devils River, and the Pecos River, among others.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the Texas and Mexico border. It is fed by the Rio Grande, Devils River, and the Pecos River, among others.

Cave formations depend on water flowing through the limestone that makes up the cave walls. As the water passes through, it dissolves the limestone. Then, the calcium recombines with carbon dioxide in the water to create calcium carbonate.

A series of flowstone draperies in the Caverns of Sonora.

A pool in the Caverns of Sonora. This cave, like many others, was formed by water combining with carbon dioxide to create a weak carbonic acid. This acid then dissolved the limestone to carve out chambers.

A prominent cave column in the Caverns of Sonora. Cave columns occur when stalactites and stalagmites fuse together. This column then grew a series of cave formations, or speleothems, known as "cave popcorn."

A series of bulbous cave formations known as "cave popcorn." The geode-like formation in the center developed, because, at one point, this portion was submerged in water. Water was moving on the surface, creating the smooth appearance, while the opening allowed water to pool.

A series of stalagmites, a form of dripstone that grows from the floor of a cave, in the Caverns of Sonora.

A series of speleothems, or cave formations, in the Caverns of Sonora.

Amistad National Recreation Area includes the Amistad Reservoir, a man-made lake along the border of Texas and Mexico.