Some images are recent - there are collections from the Hawaii Volcano Observatory and the Mount St. Helens eruptions, for instance - but a number of amazing photos come 19th and early 20th century expeditions to the Western US, some of the earliest geologic expeditions in the history of the United States. There are also collections organized by National Park, historical earthquakes, mines and quarries, and photographers. It's a great resource, and even though a lot of the photos are black-and-white images, they're no less useful as teaching aids. Best of all, they're free: since the USGS is a government agency, anyone can use these images in any publication. They come in multiple sizes and resolutions (the largest is more than 1600 dpi, which is more than adequate for a professional publisher's needs).
The U.S. Geological Survey (USGS) Central Regional Library maintains a collection of over 400,000 photographs taken during geologic studies of the United States and its territories from 1868 to the present.
These images provide a visual history of the discovery, development, and sciences of the United States and its Geological Survey. Some photographs have been used in USGS publications, but most have never been published.Currently, this website represents less than 10 percent of the Library's images with approximately 30,000 photographs on-line.
Here are a few of my favorites:
(Yes, that Powell. This is a spiffy image - if you cross your eyes at it, you can see the 3D view.)
"Splintered tree on Coldwater Ridge after May 18 eruption of Mount St. Helens. Geologist for scale. Skamania County, Washington. May 19, 1980. Lipman, P.W." (mlip0049)
"San Francisco, California, Earthquake April 18, 1906. Agassiz statue at Stanford University. April 1906. Mendenhall, W.C." (mwc00715)
"Hawaii Volcanoes National Park. 1969-1971 Mauna Ulu eruption of Kilauea Volcano. Mauna Ulu dome fountain (artesian type), 50 to 75 meters in height. Photo by J.B. Judd, October 11, 1969." (hvo00094)
If you're looking for lecture material, photos for a publication, or you just want to waste time drooling over pretty pictures, this is a great resource.