October 13, 2000 Tsunami: Altar Volcano, Ecuador

Reference #14372:

At 0558 on 13 October [local] a large block of andesitic breccia with a volume of ~1.5 x 10 m broke from the N wall of La Monja Grande (The Great Nun), a snow- and ice-covered peak near the summit of the Plio- Pleistocene stratovolcano Altar. The catastrophic fall was likely facilitated by frost wedging that slowly developed and enlarged fractures throughout the rock. The block fell 900 m and landed in the E end of Laguna Amarilla (Yellow Lagoon) within the summit caldera. The impact to the lake generated an initial wave 50 m in height and smaller successive waves that ejected 1.5-3.0 x 10 m of water and sent it hurtling down the W side of the mountain.

The water eroded the slope along its path and picked up glacial moraine material, mud, and large blocks, becoming a debris flow […] The flow destroyed three of four houses located in the Able Urco community, and swept away livestock, including 80 cows and 23 horses. The flow reached the Blanco River and eroded the banks of this section up to 30 m in height. Thirteen people were killed by the oncoming flow before it reached the Chambo River, where the valley widens. This caused a decrease in flow velocity and deposition of material in an alluvial fan. The fan managed to partially dam the river, temporarily creating a lagoon of 1.5 km in length.

Reference #14371:

The maximum observable height of the subsequent tsunami wave has been of about 125 meters above the lagoon level, that is, more or less 4,310 meters above sea level, eroding the local moraine deposits […] This tsunami occurred on a Friday the 13th of October 2000 and the resulting wave killed some ten persons and hundreds of animals of the livestock