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Cinder Cones

The smallest, simplest, and most common type of volcano

Article by: , PhD, RPG

Cinder Cone Volcano

Cinder Cone Volcano: A photograph of Parícutin, the world's most famous cinder cone. It erupted and grew between 1943 and 1952 and is located near the city of Uruapan, Mexico. Today it is a volcano that is 1,391 feet in height and surrounded by about 90 square miles of lava flows. Photo by Brian Overcast / Alamy Stock Photo.

What Are Cinder Cones?

Cinder cones are the smallest and the simplest type of volcano. They are the world's most common volcanic landform. As the name "cinder cone" suggests, they are cone-shaped hills made up of ejected igneous rocks known as "cinders".

These small volcanoes usually have a circular footprint, and their flanks usually slope at an angle of about 30 to 40 degrees. Most cinder cones have a bowl-shaped crater at the top.

Cinder cones are found in many parts of the world, including: Australia, Canada, Chile, France, Iceland, Italy, Japan, Mexico, New Zealand, Peru, the Philippines, Russia, Turkey, and the United States.

Cinder Cone Eruption

Cinder Cone Eruption: A night-time view of Parícutin erupting cinders which are so hot that they are incandescent as they fly through the air - and also after they land. Photo by JSM Historical / Alamy Stock Photo.

How Do Cinder Cones Form?

Cinder cones form when molten rock known as "magma" approaches Earth's surface. The magma that forms cinder cones contains a tremendous amount of dissolved gas - and that gas is what powers a cinder cone eruption.

Some gas-charged magmas contain several percent volcanic gas on the basis of weight.

Think about that - several percent gas - on the basis of weight.

That is a tremendous amount of gas!

When the magma breaks through Earth's surface, the confining pressure on the gas is suddenly removed. The release of confining pressure causes the gas to expand as an explosive eruption that launches a spray of molten rock into the air.

The molten rock cools as it flies through the air, and the cinders rain down onto the surrounding landscape. Most of the cinders land close to the vent, and these are what build the cone. Many cinder cones blast cinders a mile or more from the vent, and the wind often assists in their spread.

Scoria cinder cone

Scoria Cinder Cone: Artistic drawing illustrating the subsurface magma source and layer-by-layer build-up of scoria in a cinder cone eruption. Image by USGS.

How Large Are Cinder Cones?

Most cinder cones are only a few dozen to a few hundred feet tall. Some of the largest are over 1000 feet tall. Some cinder cones grow to over one mile in diameter at their base, but most are smaller.

Cinder cones are small because the eruptions that build them are usually brief and produce a small volume of ejecta. Many cinder cones have just one episode of activity.

Some cinder cones grow larger over a sequence of eruptions - with each successive eruption adding another layer of cinders. The accompanying illustration shows the internal structure of a cinder cone that has grown taller and wider from several eruptive episodes.

What Are Cinders?

"Cinders" are small pieces of igneous rock that have been blown from the vent of a cinder cone. They usually have a composition similar to basalt and contain numerous vesicles. Vesicles are small, round, bubble-like cavities that owe their presence to small amounts of gas that were trapped in the rock at the time of its solidification.

Geologists use the name "scoria" for rocks that have a basaltic composition and a vesicular texture. The names scoria and cinders are often used interchangeably. The color range of cinders goes from black, to dark gray, to deep reddish brown.

These small pieces of rock obtained the name "cinders" because they look like the ash produced in a coal furnace, which English-speaking people have called "cinders" for many generations. Larger pieces are sometimes called "clinkers" for the same reason, and because they sometimes make a "clinking" noise when they impact one another.

Tephra / Pyroclastic Terminology *

Geologic Name Coal Furnace Terminology ** Particle Size
Blocks / Bombs "clinkers" > 64 mm (2.5 inch)
Lapilli "cinders" < 64 mm (2.5 inch)
Volcanic Ash "ash" < 2 mm (.079 inch)
Volcanic Dust
(Fine Volcanic Ash)
"ash" < 0.063 mm (0.0025 inch)
* "Tephra" and "pyroclastics" are generalized names used for particles of igneous rocks of various sizes that have been ejected from volcanoes. They are classified by size. The terms "ash" and "dust" communicate a specific size of tephra or pyroclastic particles. These are summarized in the table above. ** Coal furnace terminology is provided for entertainment and the particle sizes are not specific.

What Is Ejecta?

The names "ejecta" and "tephra" and "pyroclastics" are all used for the rock fragments blown from a cinder cone or other type of volcano during an explosive eruption.

Many scientists use the terminology in the accompanying table when they talk or write about materials ejected from a cinder cone or other type of volcanic eruption.

The names in the table are a classification of ejecta according to the particle size. They facilitate accurate communication.

Cinder Cone and Lava Flow

Cinder Cone and Lava Flow: Photo by Tom Bean / Alamy Stock Photo.

Do Cinder Cones Make Lava Flows?

Yes. Many cinder cones produce lava flows, but they might not emerge the way you expect.

The first phase of a cinder cone eruption is the phase that produces the cinders. After the pressurized gas that propels the cinders is exhausted, the second phase that produces a lava flow sometimes occurs.

During the second phase, lava emerges from the Earth beneath the cone. However, the pile of cinders is not competent enough to confine the lava to the pipe that connects to the crater. So the lava, like any liquid, starts flowing downhill and "burrows" its way out. It emerges at the base of the cone on its downhill side. The accompanying photo shows a lava flow that emerged through the side of S P Crater near Flagstaff, Arizona.

Where Can I See A Cinder Cone?

Cinder cones are found in many parts of the world, including: Australia, Canada, Chile, France, Iceland, Italy, Japan, Mexico, New Zealand, Peru, the Philippines, Russia, Turkey, and the United States.

One of the best places to visit a cinder cone in the United States is at Sunset Crater National Monument near Flagstaff, Arizona. There you can get really close to Sunset Crater, a cinder cone about 1000 feet tall (305 meters), and Lenox Crater, a smaller and older cinder cone that is about 300 feet tall (91 meters). Sunset Crater is not an active volcano. It formed about 1000 years ago. You can also get up close and examine the Bonito Lava Flow.

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