Cotopaxi                                            THE DANGER WITHIN




the great lahars of 1877

In January of 1877, and eruption started on Cotopaxi that would initiate one of the longest-travelling mudflows in history.18 Although there was little known about the volcano at the time, it had been active and having frequent eruptions since about 1844.2 This eruption, however, was substantially larger with a VEI of 4, rather than the consistent 2-3 VEI eruptions that Cotopaxi had been experiencing for over a century.2 The mountain's snow-capped peaks rumbled as tephra and lava were ejected from the vent, and the heated snow mixed with ash and melted, causing a huge mudslide that travelled up the Chillos valley to the Pacific Ocean, down the Rio Cutuchi to the south and the Rio Napo to the east, stopping in the Amazonian basin.13 The longest lahar, which reached the Pacific Ocean, travelled a total distance of over 326 km.13

The following is a longitudinal profile of the main river systems that drain Cotopaxi's melted snow and channel its lahars.13 The Muddy River and Drift River are from Mount St. Helens and the Redoubt volcanoes, respectively, to show comparison.13 The dots indicate major towns and cities that the river systems pass through.


This is a map of Cotopaxi Volcano and the surrounding valleys and mountains.13 The black lines indicate the directions in which the 1877 lahars travelled.13 Note the distance the north-flowing lahar had to travel to reach the ocean.


Below is an outline of the major drainage streams of Cotopaxi from the southwest, as well as the direction in which the Latacunga Valley lahar travelled.13 Note all of the towns affected, including Latacunga, which has a current population of 143, 979.14



The exceptional events of the 1877 eruption were by no means expected. However, if the key to the future is indeed in the past, then the threat of such an event occurring again is indeed something to consider when assessing this volcano's danger. Towns such as Latacunga are not well-equipped or prepared to deal with the devastation that a massive lahar could bring. This student knows first-hand, having travelled through Latacunga and seen the path that a lahar would travel. It is for this reason that this page was specifically created: to highlight the dangers that lahars, among other hazards, pose to the towns and villages that not only surround Cotopaxi but that are on its river channels. The devastation and loss of life that might result from a massive lahar is not to be taken lightly.


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