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
August 29, 2026
Aug. 29, 2026 Researchers have discovered a way to turn notoriously difficult-to-recycle PVC plastic into a key ingredient used in high-performance lubricants such as engine oil. The technique could give mountains ...
Aug. 29, 2026 Researchers have discovered that Western Australia’s iron-rich rocks can naturally generate hydrogen and that the process may be boosted to produce much larger amounts. If it can be scaled up, the vast formations beneath the Pilbara could become a ...
Aug. 28, 2026 More than 1,000 volunteers buried cotton underwear across Switzerland to help scientists measure how active different soils are. The faster the fabric disappeared, the more biological activity was taking place underground. Gardens showed the fastest ...
Aug. 27, 2026 Beneath the rocky slopes of Mount Timpanogos lies far more ice than anyone walking across the surface might suspect. Researchers used gravity measurements to map the buried glacier in 3D and found it is about 83% ice, with enough frozen water to ...
Aug. 26, 2026 A Manhattan-sized ice island has broken away from Greenland’s Petermann Glacier after years of growing fractures weakened its floating ice tongue. Scientists expect two more huge sections could soon detach, potentially removing about 22 percent of ...
Aug. 25, 2026 Scientists may have solved the mystery of why Antarctica froze millions of years before the Arctic. Slow-moving waves deep inside Earth gradually lifted East Antarctica, building mountains and a high plateau where snow and ice could survive even in ...
Aug. 25, 2026 A huge section of Greenland’s Petermann Glacier has snapped off, forming an ice island about the size of Manhattan. Satellites watched cracks spread rapidly before the 76-square-kilometer slab finally broke free on August 4. It is the glacier’s ...
Aug. 25, 2026 Scientists have created a highly efficient catalyst that breaks down stubborn lignin from plant waste into useful chemicals under relatively mild conditions. By revealing exactly how the catalyst works at the atomic level, the discovery could help ...
Aug. 23, 2026 An abandoned farm field became a flourishing wildflower meadow within little more than a decade, with plant diversity doubling and thousands of orchids appearing naturally. The discovery suggests that simply giving nature time to recover could be a ...
Aug. 20, 2026 A colossal cliff system created as the supercontinent Rodinia broke apart may have exposed the heart of the Grand Canyon nearly a billion years before the Colorado River carved it. The ancient landscape could also help explain why enormous sections ...
Aug. 20, 2026 The “Asian Water Tower” is losing roughly 24.2 billion tonnes of groundwater every year, with some of the worst declines hitting densely populated farming regions. Glacier melt may temporarily ...
Aug. 18, 2026 A newly discovered Arctic process can dramatically boost the number of particles that help form clouds. Near melting sea ice, sunlight reacts with chemicals released by the ocean, algae, and ice, ...
Latest Headlines
updated 12:56 pm ET
Aug. 20, 2026 Spain’s total solar eclipse delivered an unexpected sight: a corona glowing gold instead of its usual pearly white. Because the Sun was setting, its light passed through more atmosphere, while ...
Aug. 15, 2026 Rising carbon dioxide in the atmosphere may be leaving a measurable imprint inside the human body. Researchers analyzing more than two decades of ...
Aug. 14, 2026 Scientists have found that the AMOC may be far more vulnerable to rapid warming than to temperature alone. When warming happens slowly, the ocean can ...
Aug. 12, 2026 Researchers have found a clever new way to map a part of Earth’s upper atmosphere that is notoriously difficult to observe. Using orbital data from ...
Aug. 11, 2026 Scientists have created an unusually corrosion-resistant stainless steel that could replace costly titanium components used to produce green hydrogen. The breakthrough could reduce structural ...
Aug. 11, 2026 Marine heatwaves are emerging as a threat not just to coral reefs and fisheries, but to human health and well-being. Researchers warn that unusually hot oceans can fuel stronger storms, trigger ...
Aug. 9, 2026 Deep underground, bacteria may be capable of doing something remarkable: trapping toxic uranium before it spreads. When researchers fed microbes in uranium-contaminated mine water with glycerol, ...
Aug. 8, 2026 A rare meteorite that crashed through a New Jersey roof contains evidence of ancient salty fluids, organic compounds, and amino acids from a ...
Aug. 7, 2026 Earth’s molten iron core unexpectedly reversed direction beneath the Pacific, revealing a dramatic change in the hidden engine that creates our ...
Aug. 6, 2026 Glyphosate was long thought to be safe for honeybees because they lack the enzyme the chemical targets in weeds. However, researchers found that exposed bees foraged 13 percent less after only three ...