Cinder Cone

Cinder cones, also known as scoria cones, are the simplest and most common type of volcano. They are built from particles and blobs of congealed lava ejected from a single vent. While they may lack the imposing size of stratovolcanoes or the massive footprint of shield volcanoes, cinder cones are fundamental features in many volcanic fields.

Appearance and Structure

As gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than about 300 meters (1,000 feet) above their surroundings.

The slopes of a cinder cone are typically steep, resting at the angle of repose for loose material, which is usually between 30° and 35°. The material itself consists largely of loose pyroclastics—scoria, cinders, and ash—ranging in size from small particles to large volcanic bombs. Because the material is unconsolidated, climbing a cinder cone can be difficult, as the loose rock shifts underfoot like sand.

Formation and Eruptive Style

Cinder cones are typically formed by Strombolian eruptions, which are characterized by intermittent, distinct bursts of fluid lava.

1. Gas Expansion: Basaltic or andesitic magma rises to the surface. Dissolved gases expand rapidly as pressure decreases.
2. Fragmentation: The expanding gas shreds the magma into clots.
3. Deposition: These clots cool during flight, solidifying into scoria or cinders before landing. The heaviest fragments fall near the vent, while finer ash is carried downwind.

This process builds the cone layer by layer. Interestingly, lava flows rarely issue from the top of the crater because the loose cinders cannot support the pressure of rising magma. Instead, lava flows usually breach the base of the cone or erupt from a side vent, sometimes carrying away part of the cone wall (rafting).

Life Cycle and “Monogenetic” Nature

Unlike the massive shield volcanoes and long-lived stratovolcanoes, cinder cones are often monogenetic. This means they generally erupt only once during a single episode of activity.

• Duration: Eruptions can last from a few days to several years.
• Extinction: Once the eruption ceases, the conduit solidifies, and the volcano usually stays dormant forever.
• Erosion: Because they are made of loose debris, cinder cones erode relatively quickly (in geological terms) unless cemented by younger lava flows or vegetation.

Global Distribution and Context

Cinder cones occur in almost all volcanic regions. They are found:

• On the flanks of larger volcanoes (e.g., Mauna Kea in Hawaii or Mount Etna in Italy).
• In calderas of supervolcanoes.
• As independent clusters in large volcanic fields. For example, the San Francisco Volcanic Field in Arizona contains over 600 cinder cones.

Famous Examples

• Parícutin (Mexico): The most famous cinder cone in history. In 1943, it literally grew out of a farmer’s cornfield. Over nine years, it grew to 424 meters (1,391 ft) high, providing scientists with a first-ever opportunity to document the full life cycle of a volcano.
• Sunset Crater (USA): A young, beautifully preserved cone in Arizona that erupted around 1085 AD.
• Cerro Negro (Nicaragua): A historically active cinder cone known for “volcano boarding,” where thrill-seekers slide down its steep, ash-covered slopes.