Volcanic cone

Puu ō or Puu Oo, a splash cone in Kīlauea, Hawaii.

A volcanic cone is a volcanic formation. It is located in the part where the volcano expels the magma into the atmosphere, or the hydrosphere. The ejecta from a volcanic opening tend to pile up generally forming a cone with a central crater. But depending on various factors such as the matter ejected in the eruption, they adopt different morphologies. The most common types are spatter, tuff, and scoria cones.

Splatter Cone

They are the exit holes of very fluid lava shield volcanoes. As the gas from the eruption expands, it carries portions of lava that pile up around it when it falls to the ground. This partially liquid rock drifts down and out. The individual deposits are very irregular in shape. The new contributions of material are solidified on the previous ones and are welded to them.

Cinder cone

Schematic drawing of a cone of scum

A scoria cone is a volcanic cone built almost entirely from the loose fragments of the so-called volcanic scoria (pumice, pyroclasts or tephra), that is to say, with a grain size greater than ash. They are built from particles and drops of solidified lava expelled through a single opening. As the amount of gas inside the lava expands violently into the air, it breaks it into small fragments that solidify and fall as slag around the opening to form a circular or oval cone. Most scoria cones are in the shape of an inverted bowl with a crater at the top.

Cross cones rarely rise more than 300 to 750 m above their surroundings, and tend to erode rapidly without new eruptions. When erosion occurs, the old chimney is usually exposed and forms the so-called volcanic plug.

Cinder cone or tuff cone

A cinder cone or tuff cone is made up primarily of pyroclasts, ranging in size from silt to sand, ejected from a single vent. It is usually formed in a single eruptive episode, when the magma interacts with groundwater explosive eruptions called phreatic occurs. A large amount of steam is generated. The interaction between magma, expanding steam, and volcanic gases causes the ejection of mostly small particles called ash. This falling ash has the consistency of flour. The unconsolidated ash forms a cinder cone. If the ash consolidates, it becomes a tuff cone or tuff ring.

Stratocone or stratovolcano

The Osorno Volcano in Chile is a clear example of stratovolcano.

A stratovolcano is a type of high-altitude, conical volcano surrounding a volcanic vent. Composed of multiple layers of hardened lava alternating with pyroclastic and volcanic ashes (arising from alternating periods of explosive activity and others of fluid lava flows). These volcanoes are characterized by a steep profile and periodic, explosive eruptions. The lava that flows from its interior is highly viscous and cools and hardens before it can travel far. This with the periods of eruptions rich in scoria, which are consolidated by later eruptions of lava, allows the volcano to reach a considerable height with steep slopes. If the lava were too fluid it would spread out to form a shield volcano and if it were too thick it would form an easily eroded cinder cone.

Pseudocrater

Pseudocraters, rootless cones or littoral cones are formed when a lava flow flows over a stratum with a lot of water. A steam explosion can be produced that crumbles and ejects the material, placing it above the point of the explosion forming a crater. It is called rootless craters because there is no connection to any magma chamber. A clear exponent are those from the south of Lake Myvatn in Iceland.