| During the last decade, researchers at the Cascades Volcano Observatory (CVO) in Vancouver, Washington, have taken thousands of photographs of Mount St. Helens and the surrounding area, and hundreds more of other Cascades volcanoes. They have used a great many types of cameras. Cameras are one of the most versatile and useful tools available to document changes around volcanoes. Still cameras take one picture at a time and can be divided on the basis of film size into small format, medium format, and large format. There is also an instant-processing still camera which produces a single image within 30 seconds. Video and movie cameras are used for many of the same applications as still cameras are are especially useful in oblique and illustrative terrestrial photography. Video or movie footage is valuable when studying dynamic events such as ash plumes or pyroclastic flows, or calculating the speed of lahars or floods. Vertical and oblique aerial photography, repeat and illustrative terrestrial photography, and time-lapse photography are all techniques available for documenting changes occurring on or around volcanoes. the resulting photographs and footage can be used for interpretation, illustrations in publications, scientific talks and public slide shows, quantitative measurements, and historical documentation of volcanic processes. -- Topinka, 1992 |
