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Central American Volcanoes Active volcanoes, lava flows, land use Significance: Part of the Pacific "ring of fire," the Central American Volcanic Region is not only a region of active volcanism, but of major earthquake activity as well. Many volcanoes are presently active, and others could erupt at any time. Cloud cover in this region is persistent throughout most of the year except during late November through February. Scientists will use the Shuttle photographs to map and document recent lava flows and ash deposits, vegetation regeneration, and possibly note and record an actively erupting volcanoes. Physical Characteristics: A dense field of volcanoes extends from the Mexico/Guatemala border southeastward to the Coast Rica [[Costa Rica]]/Panama border. In Nicaragua the area surrounding the volcanoes, is agriculturally productive, especially the lowlands, is agriculturally productive due to the outpourings of lava and ash which over time has enriched the soil. Along the volcanic belt in Nicaragua lie two large freshwater lakes, Lakes Managua and Nicaragua, both of which drain into the Caribbean. Active volcanoes (islands) can be seen in both lakes. Especially noteworthy in Lake Nicaragua is Ometepe Island, composed of two nearly identical volcanic cones linked by a narrow isthmus; the northern volcano has been active since 1985. The most active volcano in Nicaragua is the Masaya Caldera, a dome-shape volcano much like those of the Hawaiian Islands. The caldera itself is a wide basin some 10 kilometers by 5 kilometers, with a rim which rises on the western side to over 500 meters. Frequently an eruption plume from Masaya blows hundreds of kilometers out over the Pacific Ocean. In Costa Rica just northeast of the capital city of San Jose, are four great volcanic cones, their bases merged into one massive pedestal. This commanding line of volcanoes, with elevations reaching over 3 000 meters, parallels the main crest of the mountains, which run northwest-southeast through the center of the country. One of the most active volcanoes of the four, near San Jose, emits jets of noxious fumes from vents in its broad lake-filled crater. Arenal is a stratovolcano located in northwestern Costa Rica. Slow-moving lava flows continue to move down its sides into the populated lowlands below the mountain, as minor eruptions have been constant over the last few years. Observation Techniques: Near-vertical to low oblique photographs using the 50 mm of 100 mm lens are requested to give a broad view of the numerous volcanoes and associated fault patterns. If a volcanic eruption is observed, an oblique photograph of the cloud plume is desired. Near-vertical views using the 250 mm lens of specific volcanoes are invaluable for mapping and documenting new lava flows, ash deposits, and regrowth of vegetation. CIR film has been shown to give good discrimination between fresh and older lava units in other areas. Near-vertical stereo views of erupting volcanoes allow the height of the eruption plume to be estimated. [[bottom]] Center Point: 11.5°N, 85.5°W 148
