Images

Jewel Cave is currently the 3rd most extensive cave network in the world. It is believed to have formed completely underwater, thus leading to the extensive coating of calcite crystals.

In the center of the image, some of this coating of calcite crystals can be seen. These crystals are made up of two primary types: dogtooth spar and nailhead spar.

Piping plover chicks are well concealed in shallow nests on sandy beaches.

Jewel Cave is currently the 3rd most extensive cave network in the world. It is believed to have formed completely underwater, thus leading to the extensive coating of calcite crystals.

In the center of this image, a cave formation known as mule-ear drapery can be seen.

Jewel Cave is currently the 3rd most extensive cave network in the world. It is believed to have formed completely underwater, thus leading to the extensive coating of calcite crystals.

Trail head sign to Lower Jumpup Spring, north of Grand Canyon. 

The USGS developed an oral sylvatic plague vaccine (SPV) to help immunize prairie dogs against plague. The SPV is administered via a brightly colored, peanut butter flavored bait.

A prairie dog sits outside its burrow at the Pitchfork Ranch near Meteetsee, Wyoming.

This wild prairie dog has been tagged by scientists in an effort to study the efficacy of a USGS-developed oral sylvatic plague vaccine (SPV) to help immunize prairie dogs against plague.

This image was taken during field tests to determine the effectiveness of a USGS-developed oral sylvatic plague vaccine (SPV) to help immunize prairie dogs against plague. The SPV is administered to wild prairie dogs via a brightly colored bait.

This image was taken during field tests to determine the effectiveness of a USGS-developed oral sylvatic plague vaccine (SPV) to help immunize prairie dogs against plague. The SPV is administered to wild prairie dogs via a brightly colored bait.

The image was taken during field tests to determine the effectiveness of a USGS-developed oral sylvatic plague vaccine (SPV) to help immunize prairie dogs against plague. The SPV is administered to wild prairie dogs via a brightly colored bait.

Cages are set up next to a prairie dog burrow at the Pitchfork Ranch in Wyoming to capture free-ranging prairie dogs. Once captured, each trapped prairie dog is tagged, and a scientist takes hair, whisker, and blood samples before the animals are released back into the wild. 

Over 30 organizations and agencies are testing a USGS-developed oral sylvatic plague vaccine (SPV) at sites such as the Pitchfork Ranch in Wyoming, pictured here. If successful, the SPV could help protect endangered black-footed ferret populations in the western

The Cuyahoga Valley National Park stretches along the Cuyahoga River between Cleveland and Akron in Ohio.

The Cuyahoga Valley National Park stretches along the Cuyahoga River between Cleveland and Akron in Ohio. It is crossed by Interstate 80.

The Cuyahoga Valley National Park stretches along the Cuyahoga River between Cleveland and Akron in Ohio. It preserves the river ecology of the Cuyahoga River as well as historic transportation routes, such as the Cuyahoga Canal Towpath and the Cuyahoga Valley Scenic Railroad.

The Cuyahoga Valley National Park stretches along the Cuyahoga River between Cleveland and Akron in Ohio. It is crossed by Interstate 80.

The Cuyahoga Valley National Park stretches along the Cuyahoga River between Cleveland and Akron in Ohio.

The Cuyahoga Valley National Park stretches along the Cuyahoga River between Cleveland and Akron in Ohio.

A view of American Falls from the United States side of Niagara Falls.

A natural plume of dissolved sediments just downstream from Niagara Falls. As water travels through rock and soil, it dissolves sediments. This plume then emerges downstream from the main falls.