Viewing page 28 of 107
This transcription has been completed. Contact us with corrections.
T304A Atlas pg. 11,12 Central America Supersite There is widespread interest in comprehensive photography of Mexico and Central America by Earth Scientists in all disciplines. Below we list some of the key studies which are ongoing in this region. Two classes of environmental problem are presented, those related to volcanoes and earthquakes, and those related to deforestation and loss of biodiversity. Several of the following subsites are presented in greater detail as attachments to this Supersite. Volcanoes and Earthquakes Mexican Volcanic Zone The Central Mexican volcanic belt cuts across the country from the Pacific Ocean to the Gulf of Mexico. This region, which includes several volcanoes active in the past few decades, is also the cultural and historic center of Mexico. Including large cities like Mexico City, this heavily populated area is one of the world's most susceptible to social and economic tragedy from local earthquakes and volcanic eruptions. An example is the Mexico City earthquake in 1985. Photography in this region is important because it is one of the few regions where ground truth is available to complement Shuttle photographs. The Mexican volcanic belt is a chain of imposing volcanoes separated by large basins with restricted drainage. Mexico City sits in one of these basins between three active volcanoes: Popocatepetl, Ixtaccihuatl, and Toluca. Other volcanoes include Colima (south of Guadalajara) which is frequently active; Paricutin, the volcano which grew up in a cornfield only a few decades ago; and El Chichon, which erupted suddenly and violently in 1982. In fact, before the 1991 eruption of Mt. Pinatubo in the Philippines, the 1982 El Chichon volcanic eruption was considered to be the century's largest. The aerosol layer from that eruption lived in the upper atmosphere through 1985. Meso-American Fault Zone and Central American Volcanoes Guatemala, Honduras and El Salvador live near the function of three tectonic plates, including a subduction zone off the Pacific coast (the Middle American Trench). Several regional structures result: 1) a large shear zone across Guatemala and Honduras, including several large faults (see illustration); 2) a dense line of volcanoes and much volcanic activity down the Central American spine from the Mexican-Guatemalan border to the Costa Rican-Panamanian border (part of the Pacific Ring of Fire); 3) large earthquakes in highly populated regions. Obviously the structures are very complicated in this region. The faults may appear as large linears such as densely wooded ridges, aligned river valleys, and long escarpments. At any given time, 2-3 volcanoes, on average are active. We desire photographs of regional structures like faults or other linears, volcanic landforms, volcanic activity such as plumes, lava flows, ash and mud flows, existence of lake-filled calderas, vegetation regeneration; and spatial relationships of structures to merge with existing field knowledge. This region also experiences rapidly changing political and social climates, and changing land uses result. We also desire photographs of deforestation and vegetative cover in Central America, and environmental modifications like erosion, siltation, riverine and coastal changes. Center Point: 15°N, 90°W 128
