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The following is a partial list of terms used in Vulcanology, the study of volcanos and associated events. The terms are provided strictly as a study aids and references extracted from a much larger glossary of terms used by professionals in these fields.
Selected terms used in
the study of volcanoes and Vulcanology.
- A basaltic lava which has a rough, blocky surface.
- Andesite line
- The petrographic boundary between andesites and basalts. It marks the
boundary between explosive (felsic) and oceanic (mafic) volcanoes in the
- ash fall (air fall)
- The precipitation of airborne volcanic ash.
- Dark colored, fine grained volcanic rock which is commonly called lava.
Basaltic lavas are generally very fluid.
- A topo-volcanographical feature, usually greater that 1.5 miles in
diameter, which is formed when the top of a volcanic cone collapses downward
into the volcanic cone. Caldera will usually fill with water, creating
fourmations known as caldera lakes, often featuring a small island which
is theremains of a subsequent lava dome. An example of such a lake is Crater
Lake in the state of Oregon (USA).
- cinder cone volcano
- A topo-volcanographical feature which is generally pyramidial in appearance.
Cinder cone eruptions are generally considered to be single events where
eruptions throw pyroclastic materials into the air where they cool to cinders
and fall back to the ground, forming the characteristic cone shape.
- composite cone volcano
- A topo-volcanographic feature which is generally slightly concave upward
and consists of alternating layers of of ash and dust. Composite cones
are usually the highest and most dangerous of the the volcanic cones.
- columnar jointing
- A geologic formation formed as hot volcanic rocks cool and contract
forming polygonal columns which are usually vertical to the surrounding
lava flow terrain but may be curved. Devil's Tower in Wyoming (USA)
as a spectacular example of this kind of formation.
- A lava type comprised primarily of feldspar (fel) and silica (s) usually
found at continental boundry subduction zones. These are generally thick,
pasty lavas with high silicon dioxide levels.
- A flow of mud or debris consisting of volcanic material.
- Molten or solid ejected pyroclastic materials ranging from 4 to 32
mm in size.
- lava plateau
- A large mesa (tableland), which may have an area reaching thousands
of square miles, which is underlain by a thick sequence of lava flows.
- A broad volcanic crater formed by multiple shallow explosive eruptions.
Maars will commonly contain a lake and are surrounded by a low ring of
ejected materials. (Also see phreatic eruption)
- A lava type comprised primarily of magnesium (ma) and iron (fe) usually
found at the mid-ocean ranges and hot spots. These yeail fluid lavas which
retain very little gasses and generally do not erupt as violently.
- nuee ardente (ash flow)
- A very hot, dense cloud of volcanic ash and other pyroclastic material
which is produced by explosive deisintegration of viscous lava in a vent
and travels very rapidly down the slope of a volcano.
- A lava flow which has smooth, billowy, or ropy surfaces.
- phreatic eruption
- Volcanic eruption, consisting mostly of steam, which is caused by the
interaction of magma and steam.
- A descriptive term used to identify fragmented material--ash, cinders,
blocks, and bombs--which is ejected from a volcano.
- shield cone volcano
- The largest types of volcano (areawise) composed of piles of usually
basaltic lava in a usually-gentle convex upward slope. These volcanoes
are most commonly identified with Hawaii and Iceland.
- The name given to pyroclastic materials of all shapes and sizes.
- A large sea wave which is produced by a submarine earthquake, landslide,
or volcanic eruption. Commonly called a tidal wave.
- volcanic ash
- A very fine, gritty volcanic dust whose particles are less than 4mm
- volcanic dome (lava dome volcano)
- Steep-sided protrusions of viscous, glassy lava. Often found within
the crater of a large volcano or caldera but may be free-standing.
- VEI (Volcanic Explosivity Index)
- A scale for rating the volcanic eruptions according to the volume of
material ejected, the height to which the material rises, and the length
of time over which the eruption continues.
- volcanic hazardst
- Ash flows and ash falls, debris flows (lahars), gases, peripheral landslides,
lava flows, tsunami and weather changes. Of these, lava flows are the most
potentially destructive however ash falls and release of gasses can cause
serious health and respiratory problems including death by asphyxiation.
- veil index (dust veil index)
- A measure of the effect of volcanic dust on incoming solar radiation
and resulting effects on regional or global climate.
- welded tuff
- A glassy pyroclastic material which has been made hard by the weldingtogether
of its particles by the action of retained heat.
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