A nuee ardent, or "glowing cloud," is a type of explosive volcanic eruption characterized by a dense, very hot mass of ash, gasses, and volcanic material traveling down a volcanic slope at high velocity. A nuee ardent, also called a pyroclastic flow, can reach speeds of 450 mi/hr (720 km/hr) and temperatures of 1,500°F (830°C). They can travel as much as 124 mi (200 km) from the source and cover areas as large as 12,000 mi2 (20,000 km2). The volume of transported material can be as large as 250 mi3 (1,000 km3) or more.
Nuees ardentes can be destructive and deadly. An eruption of Mount Pelee, Martinique, in 1920 produced a nuee ardent that, within minutes, killed 30,000 inhabitants of a nearby town. In 1982, eruptions and pyroclastic flows from El Chichòn Volcano , southeastern Mexico, killed 2000 people, in villages as far as 5 mi (8 km) from the source.
Nuees ardentes are typically composed of two parts; a basal or lower part that hugs the ground and contains the larger volcanic fragments, and an upper part composed of a turbulent mix of hot ash and gas. When cooled, the gas and ash can form pumice , a very porous and lightweight volcanic rock .
Pyroclastic flows commonly are produced either by the downslope movement of fragments ejected upwards as they fall back, or by explosive eruptions that pulverize existing rock and throw the rock, ash, and gas in a more horizontal direction. In many cases, pyroclastic flows result from a combination of mechanisms. The sequence of events leading up to and during the 1980 eruption of Mount St. Helens illustrates some of the complexity of the process. An increase in seismic activity beneath the volcano in March marked the beginning phase of the eruption. Magma injected into the cone of the volcano at high pressure created a bulge on the north flank that grew outward at rates as high as 8.2 ft (2.5 m) per day. For the next two months only minor eruptions occurred. On May 18, a 5.1 magnitude earthquake triggered a series of massive landslides of material over the bulge. Remove of this material destabilized the north slope, which failed explosively releasing a pyroclastic flow horizontally. The eruptions flattened trees and killed wildlife in a 212 mi2 (550 km2) area . The eruption removed the upper 1,300 ft (400 m) of the cone and left a crater 2,000 ft (625 m) deep, 1.7 mi (2.7 km) long, and 1.3 mi (2.0 km) wide.
"Nuee Ardent." World of Earth Science. . Encyclopedia.com. (November 21, 2018). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/nuee-ardent
"Nuee Ardent." World of Earth Science. . Retrieved November 21, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/nuee-ardent
Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).
Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.
Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:
Modern Language Association
The Chicago Manual of Style
American Psychological Association
- Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
- In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.