Scoria

Scoria is a textural term for macrovesicular volcanic rock ejecta. It is commonly but, not exclusively of basaltic or andesitic in composition. Scoria is light as a result of numerous macroscopic ellipsoidal vesicles, but most scoria has a specific gravity greater than 1, and sinks in water. The vesicularity results from the exsolution of magmatic volatiles prior to chilling. Scoria differs from pumice in having larger vesicles and thicker vesicle walls, and hence is typically darker in colour (generally dark brown, black or red) and denser. The textural difference is probably the result of lower magma viscosity, allowing rapid volatile diffusion, bubble growth, coalescence, and bursting. Scoria may form as part of a lava or as fragmental ejecta (lapilli, blocks and bombs) for example at Strombolian eruptions that form steep-sided scoria cones. Most scoria is composed of glassy fragments, and may contain phenocrysts. An old name for scoria is cinder. Scoria. ... Scoria. ... In volcanology, ejecta consists of particles that came out of a volcanic vent, traveled though the air or under water, and fell back on the ground surface or on the ocean floor. ... For the cities, see Basalt, Colorado and Basalt, Idaho. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Cinders are nut-sized pieces of red or black rock fragments resulting from the ejection of liquid lava that are uncemented vitric, vesicular, pyroclastic material, more than 2. ...

Creation

Scoria

As rising magma encounters lower pressures, dissolved gases are able to exsolve and form vesicles. Some of the vesicles are trapped when the magma chills and solidifies. Vesicles are usually small, spheroidal and do not impinge upon one another, instead they open into one another with little distortion. Volcanic cones of scoria can be left behind after eruptions, usually forming mountains with a crater at the summit. An example is Mount Wellington, Auckland in New Zealand, which like the Three Kings Mount in the south of the same city has been extensively quarried. Quincan, a unique form of Scoria, is quarried at Mount Quincan in Far North Queensland, Australia. Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2272 × 1704 pixel, file size: 2. ... Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2272 × 1704 pixel, file size: 2. ... Puu Ōō, a cinder-and-spatter cone on Kīlauea, Hawaii Volcanic cones are among the simplest volcano formations in the world. ... Mount Wellington is a peak and a suburb in Auckland City, New Zealand The peak Mount Wellington is a 137 metre volcanic peak located in the Auckland volcanic field of Auckland, New Zealand. ... Three Kings is a suburb of Auckland, New Zealand, named after the three-peaked volcano within it. ... Mount Quincan is a volcanic mountain near Yungaburra on the Atherton Tableland in Far North Queensland, Australia. ... Map of Far North Queensland Far North Queensland (abreviated to FNQ) is a region of Queensland covering the northern part of the state. ...

Tuff Moai with red Scoria Pukao on its head

The quarry of Puna Pau on Rapa Nui/Easter island was the source of a red coloured scoria which the Rapanui people used to carve the Pukao (or top knots) for their distinctive Moai statues, and to carve some Moai from. Image File history File linksMetadata Download high resolution version (1704x2272, 566 KB) A close up of the moai at Ahu Tahai, restored with coral eyes by the American archaeologist William Mullo. ... Image File history File linksMetadata Download high resolution version (1704x2272, 566 KB) A close up of the moai at Ahu Tahai, restored with coral eyes by the American archaeologist William Mullo. ... Welded tuff at Golden Gate in Yellowstone National Park Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. ... Ahu Tongariki, restored in the 1990s Moai are monolithic stone figures on Rapa Nui / Easter Island, Chile. ... Moai statue with its Pukau Pukao are the hats or topknots that some Rapa Nui (Easter island) Moai (statues) used to have. ... Punau Pau is a quarry in a small crater or cinder cone on the outskirts of Hanga Roa in the South West of Easter Island (a Chilean island in the Pacific Ocean). ... Easter Island and its location Easter Island (Polynesian: Rapa Nui (Great Rapa), Spanish: Isla de Pascua) is an island in the south Pacific Ocean belonging to Chile. ... “Rapa Nui” redirects here. ... The Rapanui or Rapa Nui (Big Rapa) are the native Polynesian inhabitants of Easter Island in the Pacific Ocean (the island itself is also called Rapa Nui). ... Moai statue with its Pukau Pukao are the hats or topknots that some Rapa Nui (Easter island) Moai (statues) used to have. ... Ahu Tongariki, restored in the 1990s Moai are monolithic stone figures on Rapa Nui / Easter Island, Chile. ... Ahu Tongariki, restored in the 1990s Moai are monolithic stone figures on Rapa Nui / Easter Island, Chile. ...

Reticulite ("thread-lace scoria") differs from scoria in being considerably less dense. It is formed from a thin layer of froth occurring on some basaltic lava flows due to the bursting of vesicle walls. The thin glass threads are the intersections of burst vessicles. This is the lightest rock on earth with its specific gravity less than 0.3. The delicate framework of thread-lace scoria is so open that the average porosity is 98-99%. Relative density (also known as specific gravity) is a measure of the density of a material. ... Porosity is a measure of the void spaces in a material, and is measured as a fraction, between 0–1, or as a percentage between 0–100%. The term porosity is used in multiple fields including manufacturing, earth sciences and construction. ...

See also

• Cinder
• Tuff
• Pumice
• Volcanoes
• List of rock types
• Rock (geology)