Debris avalanches occurred thousands of years ago near the Nevado del Ruíz
A first study carried out in Colombia concluded that approximately 40,000 years ago there was a dry rock avalanche without lava flow.Bogotá D. C., 06 de abril de 2015 — Agencia de Noticias UN-
The yellow dots are mounds identified in the area where the avalanche rocks scattered. Photos: Courtesy of Laura Velásquez
Debris avalanches are large landslides produced by volcano flank instability. This phenomenon is more common and known in places such as Japan and United States.
A research project held by the UNal Department of Geosciences discovered remnants of this phenomenon in an area known as Las Nereidas in the Province of Caldas, to the west of the Nevado del Ruiz. During the field work researchers discovered 281 mounds which prove the occurrence of this geologic and volcanic event.
If an avalanche of this kind occurred today, it would level everything in its path. However at Las Nereidas the effect produced thousands of years ago changed the topography of the area.
As claimed by Laura Vanessa Velásquez, responsible of this research project and directed by Professor John Jairo Sánchez. According to Velásquez, by performing a literature review and other studies they discovered that before the landslide the area was a plateau, although a bit sloped towards the west.
“The phenomena studied are the product of the collapse of a volcanic structure or cone which fractured due to seisms or strong rains and moved at great speeds,” said Velásquez,.
The moving material is varied forming small mounds as the ones found in Las Nereidas. The researchers identified 281 mounds which match the bearing of the avalanche. The avalanche covered a total of 47.7 square kms (18.47 square miles) and horizontal distance of 17.8 kms (11.06 miles) and 2.6 kms (1.61 miles) vertical distance.
First they thought it had begun at the Arenas crater of the Nevado del Ruiz and on the other side a scar in the area related to the amphitheater which is the area remaining after part of the volcano collapsed.
“The second hypothesis has been the one more related to the study, even more so when there are indications of the presence of another volcano,” said Velásquez.
Being the first study on avalanches, this research project turns into reference material on these types of geological activities, of which their existence was unknown until recently. Furthermore the project will help forecast future events of this kind.(Por: Fin/DSGM/DMH/SYC