Volcanic Activity
Throughout history, Cotopaxi has caused devastation with some of its eruptions, even from the time in which the Conquistadors entered Quito in 1534. The majestic volcano, is perpetually snow covered from an altitude of 16,404 ft. (5,000 m) where its glaciers are found. Cotopaxi volcano, is located at 37 miles (60 Km) south of Quito and 21 miles (35 Km) northeast of Latacunga, the capital of Cotopaxi province. Since 1532, Cotopaxi experienced five eruptive cycles in 1532-1534, 1742-1744, 1766-1768, 1854-1855 and 1877-1880, with at least 13 major eruptions within these cycles. Surprisingly, during the twentieth century, the volcano was not very active, presenting no major eruptions; 136 years have passed since the last great eruption in 1877. These eruptions often generated falls of ash, pumice and scoria (crust like lava), lava flows, pyroclastic flows and lahars, or mudflows that severely affected the surrounding areas, resulting in the creation of numerous valleys around the volcano. In the eruption of 1877, it was reported that the city of Quito spent 24 hours of darkness and that about 0.4 in (1 cm) of ash accumulated in the city. In the last eruption, huge debris flows were generated as a result of ash flows melting the icecap. Mothes (1992), and Hall and Mothes (1997) reported that in the eruption of 1877, the debris flow arrived at the ocean in 18 hours, covering a distance of 326 km. An event of similar magnitude if it were to occur today, would directly affect more than 80000 people [Hall and Mothes, 1997, Mothes et al., 1998] (Métaxian et al., 1999). After the eruption in 1877, Cotopaxi continued with mild-to-moderate activity for several years. In subsequent years, sporadic explosions caused some light fall of ash in various areas in the western flank of the volcano. “The latest report of activity in the volcano was a possible explosion of small size which occurred in February 1942, although this date has not been able to be upheld with certainty” (Andrade et al., 2005). |
Associated Danger and Impact to the Population
The volcanic phenomena associated with all of the eruptions of Cotopaxi are: ash fall, lava flows, pyroclastic flows, mud flows and lahars. These volcanic phenomena severely affected the surrounding areas of the volcano, causing significant damage to property, livestock, fields, farmers even the loss of human lives, leaving this region with an economic crisis. “The eruptions of Cotopaxi that launched pyroclastic flows, ash, and lahars were traveling at such a speed that it took about 30 minutes to reach the city of Latacunga, less than one hour to get as far away as Quito and Los Chillos valley, and close to 18 hours to get west and reached the zone of Esmeraldas where the Esmeraldas river meets the Pacific Ocean on the coast of Ecuador” (Andrade et al., 2005). One of the main concerns in case of a huge eruption of Cotopaxi would be the flow of mud and ice from its glacier, or lahars. These lahars may have large volumes and could cover very large areas, affecting major infrastructure and populated areas several miles away from the volcano. The affected areas would be the cities of Latacunga, Sangolquí, San Rafael, Tumbaco and all areas until Esmeraldas located on the coast of the Ecuador. Computer models calculated lahars of eight meters deep coming down from the direction of the Pita River toward the valley of Los Chillos, now a main suburban area of Quito, with a population of more than 100,000 people. In the event of an explosive eruption, not much would be left of those settlements in the valley. According to the research of the IG, it is possible to say that rhyolitic eruptions, or explosive eruptions, of Cotopaxi occur approximately every two thousand years. Since the last eruption of huge magnitude of Cotopaxi occurred 2300 years ago, it is important to have a cautious plan of how to deal with this type of explosive activity. Latacunga is the capital city of the Cotopaxi Province, 55 miles (89 km) south of Quito. The population of Latacunga is about 50,000, largely mestizo (mixed Spanish origin and indigenous). It is 9,055 ft. (2,760 m) above sea level. Its climate is often relatively cold and windy. The active volcano Cotopaxi is only 16 miles (25 km) away, and the town has suffered repeatedly from eruptions. Latacunga’s economy depends on agriculture, and floriculture. It has an international airport that is used as an Air Force base and for some special commercial flights. The presence of volcanic activity has led to the accumulation of pumice deposits which are currently mined, as well as the presence of natural sparkling water, which is bottled under the brand name San Felipe. Latacunga lies within the range of significant ash fall from Cotopaxi and Tungurahua volcanoes, as well as more distal fall from other central Ecuadorian volcanoes. A large proportion of the city is within the area of historic lahars. The city of Latacunga lies in a hazard zone, such that in case of eruptions, much of the city is at risk. In the present, the Cotopaxi volcano is going through a phase of andesitic lava and it is probable that eruptions can be moderate, yet is important for the authorities in towns and cities of the area to have specific plans in case of eruptions so they can alert and prepare their communities. The settlements in the surrounding areas of the volcano have increased in population over the last several years, where many people work in agriculture, livestock, industry and tourism. In Ecuador, the IG, with the help of private and public industry is taking care of this important mission. Some of the techniques used for monitoring are: visual monitoring, seismicity, monitoring of fumaroles and hot springs, monitoring of surface temperature, lahar, and glaciers. In addition, the IG has published reports and maps at the areas of risk. It is important to note that the limits of the volcanic hazards shown on the maps are only approximations and do not represent absolute data. This is due to the fact that the eruptive phenomena may vary in their volume, magnitude and scope, as well as areas that are affected. |