Reference Terms
from Wikipedia, the free encyclopedia
Pyroclastic flow from volcanoes
Pyroclastic flows are a common and devastating result of some volcanic eruptions. They are fast-moving fluidized bodies of hot gas, ash and rock (collectively known as tephra) which can travel away from the vent at up to 150 km/h. The gas is usually at a temperature of 100-800 degrees Celsius. The flows normally hug the ground and travel downhill under gravity, their speed depending upon the gradient of the slope and the size of the flow.
Volumes range from a few hundred cubic metres to more than a thousand cubic kilometres, and the larger ones can travel for hundreds of kilometres although none on that scale have occurred for several hundred thousand years. Most flows are around one to ten cubic kilometres and travel for several kilometres. Flows usually consist of two parts: the basal flow hugs the ground and contains larger, coarse boulders and rock fragments, while an ash cloud rises above it because of the turbulence between the flow and the overlying air.
Related Stories
1
2
Earth & Climate News
October 3, 2026
Oct. 1, 2026 A new protective fabric boosted strawberry yields by as much as 3.56 times while blocking insects and still allowing sunlight, rain, and airflow to reach the plants. Originally inspired by research on military clothing, Plant Armor could also help ...
Sep. 30, 2026 Marine heatwaves may be only the most intense part of much longer warming events, with elevated temperatures sometimes lingering for months. Researchers found that conventional measurements underestimate total heat exposure by more than 150% on ...
Sep. 27, 2026 Scientists have streamlined a method for measuring DNA-bound phosphorus in soil, making it cheaper and easier while preserving its accuracy. The technique could reveal how soil microbes help recycle phosphorus and ultimately support more sustainable ...
Sep. 27, 2026 Scientists studying ancient Australian rocks uncovered more than 12,000 fossils from some of the oldest known eukaryotes on Earth. These early complex cells lived in settings ranging from coastal ...
Sep. 25, 2026 Scientists have captured a subduction zone off Vancouver Island in the process of tearing itself apart, revealing that these massive tectonic systems may die piece by piece rather than all at once. The discovery could help explain ancient plate ...
Sep. 24, 2026 Scientists discovered two tiny new snail species in Montenegro, showing that even Europe still holds animals unknown to science. One lives in the threatened Komarnica Canyon, where a proposed hydropower reservoir could destroy habitat before its ...
Sep. 23, 2026 The Cascadia subduction zone and northern San Andreas fault may sometimes rupture in rapid succession, according to evidence preserved in 3,100 years of ocean sediments. Researchers identified ...
Sep. 23, 2026 Some tropical trees have evolved a clever way to survive drought by taking in carbon dioxide at night, allowing them to keep their pores closed during the hot daytime and conserve water. By comparing three Clusia species, researchers discovered that ...
Sep. 23, 2026 The Arctic sea ice melt season is roughly 40 days longer than it was in 1979, yet its rapid expansion unexpectedly leveled off around 2010. Scientists say changing clouds and increasingly thin ice ...
Sep. 23, 2026 Scientists have found strong observational evidence that a key part of the Atlantic Meridional Overturning Circulation has been weakening across a wide stretch of ocean for nearly two decades. The ...
Sep. 22, 2026 Lake Powell has fallen to its lowest level on record after an exceptionally dry and warm winter left the Colorado River Basin with little mountain snow to melt. Lake Mead also reached record lows, raising concerns for a river system that supplies ...
Sep. 22, 2026 Researchers have created a concrete mixture that is both stronger and capable of absorbing carbon dioxide. The best formula, combining zeolite with bamboo biochar, boosted compressive strength by 7.48% and tensile strength by 15% compared with ...
Latest Headlines
updated 12:56 pm ET
Oct. 2, 2026 Researchers say stress on Southern California’s San Andreas and San Jacinto faults has reached some of the highest levels seen in a 1,000-year ...
Sep. 30, 2026 Mount Vesuvius’ famous 79 CE eruption has given scientists a remarkably precise benchmark for dating events deep in Earth’s past. The improved ...
Sep. 29, 2026 Scientists may have solved why the length of Earth’s day changes by a few milliseconds over decades. Subtle shifts in the inner core appear to tug ...
Sep. 26, 2026 Scientists have found that a famous 2-billion-year-old chemical signature, once thought to record a massive global change in Earth’s carbon cycle, may instead have been produced by local magma, ...
Sep. 23, 2026 Stonehenge’s six-ton Altar Stone may have been carried from Scotland to Dogger Bank by glaciers before prehistoric people transported it hundreds of kilometers to Salisbury Plain. The possible ...
Sep. 22, 2026 An amateur astronomer searching satellite maps for a Quebec camping spot accidentally discovered a massive ancient impact crater. Scientists later ...
Sep. 22, 2026 A Yellowstone super-eruption would begin not with a sudden surprise, but with weeks of increasingly alarming warning signs such as migrating ...
Sep. 21, 2026 Genetic evidence has revealed a previously unknown gentoo penguin species on the remote Kerguelen Islands and shown that gentoos actually consist of four distinct species. The discovery also ...
Sep. 21, 2026 A large Amazon study suggests the most powerful conservation move may be protecting the forests that are already standing. Preventing damage from ...
Sep. 20, 2026 Nearly three decades of Hurricane Hunter data reveal four features that can help a tilted tropical cyclone straighten its circulation and become ...