Nuée ardente from santiaguito volcano April 1973
The largest nuée ardente eruption of Santiaguito since November 1929, occurred April 19, 1973. The nuée descended the valley of the Rió Nimá II for a distance of about 4 km. The ash flow itself was restricted to the river bed, but the hot gas cloud devastated an area of more than 3 square kilometers extending hundreds of meters on both sides of the river bed. Because the ash cloud stopped about 2 km from the nearest habitations, there were no fatalities.
Bulletin of Volcanology
Rose, William I., "Nuée ardente from santiaguito volcano April 1973" (1973). Department of Geological and Mining Engineering and Sciences Publications. 168.