The heavier particles stay close to the ground and roll downhill in what we call a pyroclastic flow.    From Wordnik.com.  [Asimov's Science Fiction]

An eruption might create something called a pyroclastic flow, or high-speed avalanche of hot rocks and gas.    From Wordnik.com.  [TreeHugger] Reference

At least 90 people were killed as a superheated clouds of ash, gas and debris known as pyroclastic flows tumbled down the mountain and incinerated villages.    From Wordnik.com.  [Some Flights Resume Following Indonesia Volcano] Reference

"Monaco is also within range of pyroclastic missile danger.".    From Wordnik.com.  [Chronicles of Pern, First Fall]

Do you think you are far enough away to avoid the pyroclastic flow?.    From Wordnik.com.  [Tom McIntyre Explains His Picks for our 2009 Hunting and Fishing Heroes and Villians Face-Off] Reference

I could be seein the path of the pyroclastic flow from da previous eruption.    From Wordnik.com.  [pwning ur elders - Lolcats 'n' Funny Pictures of Cats - I Can Has Cheezburger?] Reference

The Miocene volcanic rocks are mostly andesite, basalt, and pyroclastic rocks.    From Wordnik.com.  [Santa Monica Mountains (Bailey)] Reference

Not only are there the usual hazards of falling ash and pyroclastic flows, but.    From Wordnik.com.  [AREA AROUND THE COLIMA VOLCANO Area around the Colima volcano] Reference

Do you think he would give of pyroclastic flows and a tidal wave after he goes critical?.    From Wordnik.com.  [Think Progress » Limbaugh: Volcanic eruption in Iceland is God’s reaction to health care’s passage.] Reference

Miocene basalt, andesite, pyroclastic, and marine sedimentary rocks predominate in this subsection.    From Wordnik.com.  [Northern Channel Islands (Bailey)] Reference

He also felt a pang of near terror as he saw the mass of things to be removed from pyroclastic activity.    From Wordnik.com.  [First Fall]

The effects of pyroclastic flows will be localized ... say, only about thirty or forty miles from the caldera.    From Wordnik.com.  [Asimov's Science Fiction]

Dominant soils are Inceptisols formed from volcanic ash or pumice, with large components of pyroclastic materials.    From Wordnik.com.  [Aleutian Oceanic Meadow - Heath Province (Bailey)] Reference

These appear to be the biggest manifestations on our planet of a rare pyroclastic-flow crystallization phenomenon.    From Wordnik.com.  [The remarkable road to San Marcos, Jalisco] Reference

Now, I can see it from the distance and you can see it spewing pyroclastic flows, you can see it every now and then.    From Wordnik.com.  [CNN Transcript May 14, 2006] Reference

But, like many geologists, I too have stood on barely cooled basaltic lava non-explosive, definitely not pyroclastic.    From Wordnik.com.  [Defying Death?] Reference

Have you ever seen on television in any documentary the sheer force of a pyroclastic flowthat consists of lava and hot-ash?.    From Wordnik.com.  [Our safety demands that volcanoes and fault lines be monitored] Reference

Explosions, implosion, pyroclastic cloud, entire pulverization of both buildings is not even mentioned in the official story.    From Wordnik.com.  [Ben Cohen: My Argument with the 9/11 Truth Movement] Reference

Lava flows, ash, and pyroclastic deposits ranging from Miocene to recent in age are the principal bedrock found in these islands.    From Wordnik.com.  [Windward Islands moist forests] Reference

Two kilometers to the south lies Mount Ngauruhoe, a 2,290 m composite andesite cone of interleaved pyroclastic material and lava.    From Wordnik.com.  [Tongariro National Park, New Zealand] Reference

Everyone did have memories of Garben's spectacular eruption, seen at a safe enough distance to be clear of the pyroclastic debris.    From Wordnik.com.  [First Fall]

The Windward Islands form a volcanic island arc consisting of lava flows, ash, and pyroclastic deposits ranging from Miocene to recent in age.    From Wordnik.com.  [Windward Islands dry forests] Reference

The western crater rim is covered with buff-colored pumice, created during the last major pyroclastic eruption from Alid, some 23,000 years ago.    From Wordnik.com.  [alidphotos.html] Reference

Alid is a very late-Pleistocene structural dome formed by shallow intrusion of rhyolitic magma, some of which vented as lavas and pyroclastic flows.    From Wordnik.com.  [Geothermics Abstract] Reference

With Dr. Fisher's extensive experience and interest in pyroclastic rocks, he enthusiastically agreed to begin work on a web site about volcanic ash.    From Wordnik.com.  [Partners of the Web site, Volcanic Ash--effects & mitigation strategies] Reference

Ash and coarser particles inhaled from within a hot, dense pyroclastic flow or surge, however, almost always results in death from burns or asphyxiation.    From Wordnik.com.  [Volcanic Ash -- Effects on Health and Mitigation Strategies] Reference

Mt. Cameroon and Bioko are volcanoes, and in consequence adjacent parts of the ecoregion have soils, rocks and black sand beaches derived from pyroclastic lava and ash.    From Wordnik.com.  [Cross-Sanaga-Bioko coastal forests] Reference

Small pyroclastic surges observed using a thermal camera descended the N flanks.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

Cycles of vigorous ash venting, rockfalls, and pyroclastic flows occurred every seven to twelve hours.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

The largest historical eruption of Sarychev Peak in 1946 produced pyroclastic flows that reached the sea.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

Look at the pyroclastic flow that use moving all over lower Manhattan and even starts to move of the water!.    From Wordnik.com.  [Newsvine - Get Smarter Here] Reference

Eruption of the voluminous Ito pyroclastic flow was associated with the formation of the 17 x 23-km-wide Aira caldera about.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

I imagine seeing the pyroclastic flows from this event would have been underpants-soilingly terrifying from the ground, however.    From Wordnik.com.  [Discover Blogs]

It was accompanied by several pyroclastic flows (superfast superheated ash and rock running down the sides) as the event unfolded.    From Wordnik.com.  [Asymptotia] Reference

Potential blast damage, heavy ash fall, and worse, huge lahars and pyroclastic flows that scour out and destroy everything in their path.    From Wordnik.com.  [Yahoo! Answers: Latest Questions] Reference