volcanic material

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• Volcanic pipe — Volcanic pipes are geological structures formed by the violent, supersonic eruption of deep origin volcanoes. They are considered to be a type of diatreme . Volcanic pipes are composed of a deep, narrow cone of solidified magma (described as… …   Wikipedia

• volcanic eruption — noun the sudden occurrence of a violent discharge of steam and volcanic material (Freq. 1) • Syn: ↑eruption • Derivationally related forms: ↑erupt (for: ↑eruption) • Hypernyms: ↑ …   Useful english dictionary

• Volcanic ash — consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions,United States Geological Survey. [http://volcanoes.usgs.gov/Hazards/What/Tephra/tephra.html Tephra: Volcanic Rock and Glass Fragments.] Retrieved… …   Wikipedia

• Volcanic rock — is an igneous rock of volcanic origin. Texture Volcanic rocks are usually fine grained or aphanitic to glassy in texture. They often contain clasts of other rocks and phenocrysts. Phenocrysts are crystals that are larger than the matrix and are… …   Wikipedia

• Volcanic blocks — are fragments of rock which measure more than 64mm in size and are erupted in a solid condition. Blocks are formed from material from previous eruptions or from country rock and are therefore mostly accessory or accidental in origin. Blocks also… …   Wikipedia

• Volcanic belt — [ Trans Mexican Volcanic Belt in Mexico ] A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature (700… …   Wikipedia

• Volcanic Explosivity Index — USGS PHOTO GLOSSARY OF VOLCANIC TERMS The Volcanic Explosivity Index, or VEI, was proposed in 1982 as a way to describe the relative size or magnitude of explosive volcanic eruptions. It is a 0 to 8 index of increasing explosivity. Each increase… …   Glossary of volcanic terms

• volcanic glass — a natural glass produced when molten lava cools very rapidly; obsidian. [1830 40] * * * Any glassy rock formed from lava or magma that has a chemical composition close to that of granite. Such molten material may reach very low temperatures… …   Universalium

• Volcanic glass — A sand grain of volcanic glass under the petrographic microscope. Its amorphous nature makes it go extinct in cross polarized light (bottom frame). Scale box in millimeters. Volcanic glass is the amorphous (uncrystallized) product of rapidly… …   Wikipedia

• Volcanic plug — A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when lava hardens within a vent on an active volcano. When forming, a plug can cause an extreme build up of pressure if volatile charged magma is trapped… …   Wikipedia

• Volcanic Explosivity Index — Der Vulkanexplosivitätsindex (Abkürzung VEI, engl. Volcanic Explosivity Index) ist eine logarithmische Skala von 0 bis 8 zur Angabe der Stärke eines Vulkanausbruchs, vergleichbar mit der Richterskala für Erdbeben. Messgrößen sind die Menge an… …   Deutsch Wikipedia