Subaqueous volcano

A subaqueous volcano is a volcano formed beneath freshwater and never builds above lake level. They are commonly in the form of gently sloping tuff cones, although they can sometimes have an unvolcano-like form, such as White Horse Bluff in the Wells Gray-Clearwater volcanic field of east-central British Columbia, Canada.

Subaqueous volcanoes can be compared to subaerial volcanoes which are formed and erupt on land surface, or under the air. The major differences of volcanic eruptions are due to the effects of pressure, heat capacity or conductivity of water, the presence of steam and water rheology. The thermal conductivity of water is about 20 times that of air and steam has a thermal conductivity nearly 50 times that of water. Subaqueous volcanoes are most commonly formed in oceans, but can also form in lakes, rivers and subglacial lakes. In improving our understanding of subaqueous volcanoes, it is important to consider the differences between the characteristics of modern and ancient approaches to the study. Modern studies offer fresh and unaltered observances, can see and map surface features and the water depth is known in areas that allow observation. Ancient studies have had stratigraphic exposure to sections, are easier to work on, have more and better exposures and have an existing relationship to resources.

Some geologists would restrict the term subaqueous pyroclastic flow deposits to volcaniclastic units that show characteristics of emplacement in a hot state deposited underwater—however, this can’t always be done because of the subsequent process of alteration/diagenesis such as active hot springs and associated hydrothermal alteration. Deposits from pyroclastic flows that interact with water and are transformed into water-supported mass flows are called subaqueous pyroclastic debris flow deposits by some geologists. On the other hand, processes that are associated with eruption, transportation and deposition are notably different because of the presence of water. Such differences that the presence of water entails is the ability to vaporize when in contact with water, a high density and resulting confining pressure, high viscosity relative to air and differences in the thermal conductivities/heat capacities in the air relative to water.

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