This is an image of a pyroclastic flow going down the slopes of a volcano to the sea.
Click on image for full size
Image from: U.S. Geological Survey, photo by B. Yount
Mt. Pelee
Mt. Pelee is not a very tall volcano, in fact it is an example of what is called a "lava dome".
An extremely destructive
eruption of Mount Pelee occurred in 1902. The
coastal town of St. Pierre, about 4 miles downslope to the south,
was
demolished and nearly 30,000 inhabitants were killed almost instantly by a pyroclastic flow which swept down the mountain. Such a flow is illustrated in this picture of an Alaskan volcano.
The cloud of hot ash and gases swept into town at an estimated speed of 100 miles per hour or more. It would only have been 5 minutes for the pyroclastic flow to sweep from the volcano's summit into town.
Survivors of this eruption included one man who was in an underground jail cell, as well as sailors who were off-shore and witnessed the destruction of the city from a distance. Comments by these eyewitnesses included the following:
- "The mountain was blown to pieces, there was no warning."
- "It was like a giant oil refinery."
- "There was hurled straight toward us a solid wall of flame. It sounded like a thousand cannon."
- "The wave of fire was on us and over us like a flash of lightning. It was like a hurricane of fire."
- "The town vanished before our eyes."
You might also be interested in:

Ash is made of millions of tiny fragments of rock and glass formed during a volcanic eruption. Volcanic ash particles are less than 2 mm in size and can be much smaller. Volcanic ash forms in several ways
...more
Cinder cones are simple volcanoes which have a bowl-shaped crater at the summit and rarely rise more than a thousand feet above their surroundings. They usually are created of eruptions from a single vent,
...more
Lava can move in broad flat lava flows, or it can move through constrictive channels or tubes. Lava flows have a large surface area so they tend to cool quickly and flow slowly. The fastest unconstricted
...more
Earth’s center, or core, is very hot, about 9000 degrees F. This heat causes molten rock deep within the mantle layer to move. Warm material rises, cools, and eventually sinks down. As the cool material
...more
Many kinds of surface features provide evidence of a sliding lithosphere. When two plates move apart, rising material from the mantle pushes the lithosphere aside. Two types of features can form when
...more
Magma consists of remelted material from Earth's crust and fresh material from the aesthenosphere, relatively near the Earth's surface. When magma is erupted onto the surface in the form of lava, it becomes
...more
As the Earth cools, hot material from the deep interior rises to the surface. Hot material is depicted in red in this drawing, under an ocean shown in blue green. The hotter material elevates the nearby
...more