What's that cloud upriver? Eyewitness account of a lahar by USGS geologist Jeff Marso

Photo of footbridge crossing Rio Nima II near El Palmar, Guatemala

View upstream below the footbridge

El Palmar, Guatemala on August 14, 1989

"While surveying the Nima II river near the town of El Palmar in Guatemala, my colleague and I noticed a white steam cloud upriver. We were working about 15 kilometers downstream from an active lava dome, Santiaguito. A very heavy rainstorm was passing through that area and the likelihood that a hot lahar was on the way was immediately obvious.We scrambled out of the canyon as quickly as we could, gave our equipment to our driver who exited with the vehicle at high speed, and we raced for a nearby bridge with our cameras."

Footbridge Provides Safe View

"The cable suspension bridge was approximately 130 m long and at its lowest point 10 m above deepest part of the river channel. We made it over the channel just as the lahar rounded the bend upstream from us. What began as a dull roar now approached a deafening level."

Photo of approaching lahar

Front of lahar approaches bridge
(note brown splashing water and debris)

Here it Comes!

"As the lahar approached, rocks and mud splashed violently several meters up and out of the channel. I clearly remember wondering if we were high enough above the channel to be safe. I began taking photos as soon as the front of the lahar appeared."

Photo of lahar looking downstream from footbridge

Lahar rushes downstream (from bridge)

There it Goes

"The lahar passed below us at what seemed an incredible speed and with an overwhelming roar. The front of the flow was approximately 5 m high and filled the river channel. As the hot lahar became larger, small rocks and mud splatter were thrown onto and over the bridge. We decided that we were not high enough and ran for the safety of the far bank. There, ground vibrations made it difficult to stand and we had to shout to be heard over the roar. "

Photo of Santiaguito dome in Santa Maria Volcano, Guatamala

Santiaguito lava dome (note small eruption cloud)

Lahar Triggered by Rain and Eruption

"The lahar we witnessed was the first of several that surged 60 km down the Nima II River for a period of 3 hours. We estimated the lahar's speed at 50 km/hour. It was triggered by intense rainfall that eroded newly emplaced rock debris from the Santiaguito Dome complex perched in the crater of Santa Maria Volcano. Just 14 days before, a portion of the dome had broken off and collapsed into the headwaters of the Nima II River. This was the largest dome collapse from Santiaguito since the 1930's and it provided plenty of loose volcanic debris for water to erode away. "