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Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 2018. A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) [1] is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of 100 km/h (30 m/s; 60 mph) but is capable of reaching speeds up to ...
In northeastern China, a large volcanic eruption in the early Cretaceous caused the fossilization of an entire ecosystem known as the Jehol Biota when powerful pyroclastic flows inundated the area. The deposits include many perfectly preserved fossils of dinosaurs, birds, mammals, reptiles, fish, frogs, plants, and insects. [16]
Tephra is a generalized word for the various bits of debris launched out of a volcano during an eruption, regardless of their size. [4] Pyroclastic materials are generally categorized according to size: dust measures at <1/8 mm, ash is 1/8–2 mm, cinders are 2–64 mm, and bombs and blocks are both >64 mm. [5] Different hazards are associated with the different kinds of pyroclastic materials.
The most important characteristic of a Peléan eruption is the presence of a glowing avalanche of hot volcanic ash, called a pyroclastic flow. Formation of lava domes is another characteristic. Short flows of ash or creation of pumice cones may be observed as well. The initial phases of eruption are characterized by pyroclastic flows.
A lahar travels down a river valley in Guatemala near the Santa Maria volcano, 1989. A lahar (/ ˈ l ɑː h ɑːr /, from Javanese: ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water.
The most dangerous eruptive feature are the pyroclastic flows generated by material collapse, which move down the side of the mountain at extreme speeds [40] of up to 700 km (435 mi) per hour and with the ability to extend the reach of the eruption hundreds of kilometers. [43]
Noxious weeds can be deadly for humans, animals and other plants in your garden. Here’s how to identify a plants before you get hurt. You may have poison in your garden.
Volcanic ash plumes can form above pyroclastic density currents. These are called co-ignimbrite plumes. As pyroclastic density currents travel away from the volcano, smaller particles are removed from the flow by elutriation and form a less dense zone overlying the main flow. This zone then entrains the surrounding air and a buoyant co ...