Misplaced Pages

#608391

54-523: Rhyolite flows, breccias and hyaloclastics are the primary rocks comprising the Flat Landing Brook Formation. Locally abundant rocks include tholeiitic to transitional mafic fragmental rocks and massive flows, as well as felsic tuffs , tholeiitic pillow basalts and minor porphyritic felsic flows. Siltstone , greywacke , iron formation , ferromanganiferous shale and chert represent minor rocks. The Flat Landing Brook Formation

108-648: A soil amendment . Rhyolite is an extrusive igneous rock, formed from magma rich in silica that is extruded from a volcanic vent to cool quickly on the surface rather than slowly in the subsurface. It is generally light in color due to its low content of mafic minerals, and it is typically very fine-grained ( aphanitic ) or glassy . An extrusive igneous rock is classified as rhyolite when quartz constitutes 20% to 60% by volume of its total content of quartz, alkali feldspar , and plagioclase ( QAPF ) and alkali feldspar makes up 35% to 90% of its total feldspar content. Feldspathoids are not present. This makes rhyolite

162-535: A soil amendment . Rhyolitic tuff was used extensively for construction in ancient Rome and has been used in construction in modern Europe. Volcanic rocks : Subvolcanic rocks : Plutonic rocks : Picrite basalt Peridotite Basalt Diabase (Dolerite) Gabbro Andesite Microdiorite Diorite Dacite Microgranodiorite Granodiorite Rhyolite Microgranite Granite Pumice Pumice ( / ˈ p ʌ m ɪ s / ), called pumicite in its powdered or dust form,

216-438: A volcano . The unusual foamy configuration of pumice happens because of simultaneous rapid cooling and rapid depressurization. The depressurization creates bubbles by lowering the solubility of gases (including water and CO 2 ) that are dissolved in the lava, causing the gases to rapidly exsolve (like the bubbles of CO 2 that appear when a carbonated drink is opened). The simultaneous cooling and depressurization freeze

270-415: A composition very close to the water-saturated granite eutectic and with extreme enrichment in most incompatible elements . However, they are highly depleted in strontium , barium , and europium . They are interpreted as products of repeated melting and freezing of granite in the subsurface. HSRs typically erupt in large caldera eruptions. Rhyolite is common along convergent plate boundaries , where

324-457: A good insulator. A fine-grained version of pumice called pozzolan is used as an additive in cement and is mixed with lime to form a light-weight, smooth, plaster-like concrete. This form of concrete was used as far back as Roman times. Roman engineers utilized it to build the huge dome of the Pantheon with increasing amounts of pumice added to concrete for higher elevations of the structure. It

378-487: A handle, is an effective scrubbing tool for removal of limescale, rust, hard water rings, and other stains on porcelain fixtures in households (e.g., bathrooms). It is a quick method compared to alternatives like chemicals or vinegar and baking soda or borax . Good soil requires sufficient water and nutrient loading as well as little compaction to allow easy exchange of gases. The roots of plants require continuous transportation of carbon dioxide and oxygen to and from

432-561: A natural glass or vitrophyre, also called obsidian . Slower cooling forms microscopic crystals in the lava and results in textures such as flow foliations , spherulitic , nodular , and lithophysal structures. Some rhyolite is highly vesicular pumice . Peralkaline rhyolites (rhyolites unusually rich in alkali metals) include comendite and pantellerite . Peralkalinity has significant effects on lava flow morphology and mineralogy , such that peralkaline rhyolites can be 10–30 times more fluid than typical calc-alkaline rhyolites. As

486-587: A result of their increased fluidity, they are able to form small-scale flow folds, lava tubes and thin dikes. Peralkaline rhyolites erupt at relatively high temperatures of more than 1,200 °C (2,190 °F). They comprise bimodal shield volcanoes at hotspots and rifts (e.g. Rainbow Range , Ilgachuz Range and Level Mountain in British Columbia , Canada). Eruptions of rhyolite lava are relatively rare compared to eruptions of less felsic lavas. Only four eruptions of rhyolite have been recorded since

540-633: A result, many eruptions of rhyolite are highly explosive, and rhyolite occurs more frequently as pyroclastic rock than as lava flows . Rhyolitic ash flow tuffs are the only volcanic product with volumes rivaling those of flood basalts . Rhyolites also occur as breccias or in lava domes , volcanic plugs , and dikes . Rhyolitic lavas erupt at a relatively low temperature of 800 to 1,000 °C (1,470 to 1,830 °F), significantly cooler than basaltic lavas, which typically erupt at temperatures of 1,100 to 1,200 °C (2,010 to 2,190 °F). Rhyolites that cool too quickly to grow crystals form

594-400: A silky or fibrous fabric. The elongation of the microvesicles occurs due to ductile elongation in the volcanic conduit or, in the case of pumiceous lavas, during flow. The other form of vesicles are subspherical to spherical and result from high vapor pressure during an eruption. Reticulite is a type of basaltic pumice formed in very high lava fountains. It has an extremely low density and

SECTION 10

#1732855873609

648-668: A slab of oceanic lithosphere is being subducted into the Earth's mantle beneath overriding oceanic or continental lithosphere . It can sometimes be the predominant igneous rock type in these settings. Rhyolite is more common when the overriding lithosphere is continental rather than oceanic. The thicker continental crust gives the rising magma more opportunity to differentiate and assimilate crustal rock. Rhyolite has been found on islands far from land, but such oceanic occurrences are rare. The tholeiitic magmas erupted at volcanic ocean islands, such as Iceland , can sometimes differentiate all

702-524: Is Krakatoa . An eruption in 1883 ejected so much pumice that kilometers of sea were covered in floating pumice and in some areas rose 1.5 meters above sea level. Europe is the largest producer of pumice with deposits in Italy, Turkey, Greece, Hungary, Iceland, and Germany. Italy is the largest producer of pumice because of its numerous eruptive volcanoes. On the Aeolian Islands of Italy, the island of Lipari

756-405: Is a volcanic rock that consists of extremely vesicular rough-textured volcanic glass , which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular volcanic rock that differs from pumice in having larger vesicles, thicker vesicle walls, and being dark colored and denser. Pumice is created when super-heated, highly pressurized rock is rapidly ejected from

810-538: Is a very lightweight, porous and abrasive material and it has been used for centuries in the construction and beauty industry as well as in early medicine. It is also used as an abrasive , especially in polishes , pencil erasers , and the production of stone-washed jeans . Pumice was also used in the early book-making industry to prepare parchment paper and leather bindings. There is high demand for pumice, particularly for water filtration, chemical spill containment, cement manufacturing, horticulture and increasingly for

864-647: Is commonly pale in color, ranging from white, cream, blue or grey, to green-brown or black. It forms when volcanic gases exsolving from viscous magma form bubbles that remain within the viscous magma as it cools to glass. Pumice is a common product of explosive eruptions ( plinian and ignimbrite -forming) and commonly forms zones in upper parts of silicic lavas . Pumice has a porosity of 64–85% by volume and it floats on water, possibly for years, until it eventually becomes waterlogged and sinks. Scoria differs from pumice in being denser. With larger vesicles and thicker vesicle walls, scoria sinks rapidly. The difference

918-501: Is composed of a network of volcanic glass formed when the vesicles have almost completely coalesced. Pumice is an igneous rock with a foamy appearance. The name is derived from the Latin word pumex (meaning "pumice") which is related to the Latin word spuma meaning "foam". In former times, pumice was called "Spuma Maris", meaning "froth of the sea" in Latin because the frothy material was thought to be hardened sea foam. Around 80 B.C., it

972-745: Is entirely made up of volcanic rock, including pumice. Large amounts of igneous rock on Lipari are due to the numerous extended periods of volcanic activity from the Late Pleistocene ( Tyrrhenian ) to the Holocene. Pumice can be found all across North America including on the Caribbean Islands . In the United States, pumice is mined in Nevada , Oregon , Idaho , Arizona , California , New Mexico and Kansas . U.S. production of pumice and pumicite in 2011

1026-584: Is exposed in the Brunswick Mines area and near California Lake whereas the contact of the Flat Landing Brook and Nepisiguit Falls formations is exposed along The Narrows of the Nepisiguit River . The Flat Landing Brook Formation contains four named subdivisions: With an estimated original volume of approximately 12,000 km (2,900 cu mi) , the Flat Landing Brook Formation incorporates

1080-490: Is interpreted to represent the infill of a large caldera with a radius of about 80 km (50 mi) . The only rocks that do not seem to be related to the caldera are scattered dikes and small effusive flows of the Taylor Brook rhyolites, the latter of which probably issued from parasitic vents on the outer margins of the caldera. Rhyolite Rhyolite ( / ˈ r aɪ . ə l aɪ t / RY -ə-lyte )

1134-462: Is more often erupted as pyroclastic rock than as lava flows . Rhyolitic ash-flow tuffs are among the most voluminous of continental igneous rock formations. Rhyolitic tuff has been used extensively for construction. Obsidian , which is rhyolitic volcanic glass , has been used for tools from prehistoric times to the present day because it can be shaped to an extremely sharp edge. Rhyolitic pumice finds use as an abrasive , in concrete , and as

SECTION 20

#1732855873609

1188-421: Is often used on roadsides and ditches and commonly used in turf and golf courses to maintain grass cover and flatness that can degrade due to large amounts of traffic and compaction. Chemically pumice is pH neutral, neither acidic nor alkaline . In 2011, 16% of pumice mined in the United States was used for horticultural purposes. Pumice contributes to soil fertility in areas where it is naturally present in

1242-618: Is the middle member of the Tetagouche Group. Exposures between Route 490 and the headwaters of Flat Landing Brook are the type locality . It is conformably overlain by massive pillowed alkali basalt of the Little River Formation and conformably underlain by crystal tuff as well as quartz - feldspar augen schist of the Nepisiguit Falls Formation. The contact of the Flat Landing Brook and Little River formations

1296-521: Is the most silica -rich of volcanic rocks . It is generally glassy or fine-grained ( aphanitic ) in texture , but may be porphyritic , containing larger mineral crystals ( phenocrysts ) in an otherwise fine-grained groundmass . The mineral assemblage is predominantly quartz , sanidine , and plagioclase . It is the extrusive equivalent of granite . Its high silica content makes rhyolitic magma extremely viscous . This favors explosive eruptions over effusive eruptions , so this type of magma

1350-414: Is the result of the lower viscosity of the magma that forms scoria. When larger amounts of gas are present, the result is a finer-grained variety of pumice known as pumicite . Pumicite consists of particles less than 4 mm (0.16 in) in size. Pumice is considered a volcanic glass because it has no crystal structure. Pumice varies in density according to the thickness of the solid material between

1404-480: Is very important in horticulture, with the presence of pumice tillage is much easier. Pumice usage also creates ideal conditions for growing plants like cacti and succulents as it increases the water retention in sandy soils and reduces the density of clayey soils to allow more transportation of gases and water. The addition of pumice to soil improves and increases vegetative cover as the roots of plants make slopes more stable therefore it helps reduce erosion . It

1458-602: The pedicure process to remove dry and excess skin from the bottom of the foot as well as calluses . Finely ground pumice has been added to some toothpastes as a polish, similar to Roman use, and easily removes dental plaque build-up. Such toothpaste is too abrasive for daily use. Pumice is also added to heavy-duty hand cleaners (such as lava soap ) as a mild abrasive. Some brands of chinchilla dust bath are formulated with powdered pumice. Old beauty techniques using pumice are still employed today but newer substitutes are easier to obtain. Pumice stone, sometimes attached to

1512-617: The R field of the TAS diagram . The alkali feldspar in rhyolites is sanidine or, less commonly, orthoclase . It is rarely anorthoclase . These feldspar minerals sometimes are present as phenocrysts. The plagioclase is usually sodium -rich ( oligoclase or andesine ). Cristobalite and trydimite are sometimes present along with the quartz. Biotite , augite , fayalite , and hornblende are common accessory minerals. Due to their high content of silica and low iron and magnesium contents, rhyolitic magmas form highly viscous lavas . As

1566-525: The bubbles in a matrix . Eruptions under water are rapidly cooled and the large volume of pumice created can be a shipping hazard for cargo ships. Pumice is composed of highly microvesicular glass pyroclastic with very thin, translucent bubble walls of extrusive igneous rock . It is commonly but not exclusively of silicic or felsic to intermediate in composition (e.g., rhyolitic , dacitic , andesite , pantellerite , phonolite , trachyte ), but basaltic and other compositions are known. Pumice

1620-551: The bubbles; many samples float in water. After the explosion of Krakatoa , rafts of pumice drifted through the Indian Ocean for up to 20 years, with tree trunks floating among them. In fact, pumice rafts disperse and support several marine species. In 1979, 1984 and 2006, underwater volcanic eruptions near Tonga created large pumice rafts that floated hundreds of kilometres to Fiji . There are two main forms of vesicles. Most pumice contains tubular microvesicles that can impart

1674-401: The eruption of explosive volcanoes under certain conditions, therefore, natural sources occur in volcanically active regions. Pumice is mined and transported from these regions. In 2011, Italy and Turkey led pumice mining production at 4 and 3 million tons respectively; other large producers at or exceeding a million tonnes were Greece, Iran, Chile, and Syria. Total world pumice production in 2011

Flat Landing Brook Formation - Misplaced Pages Continue

1728-508: The eruptive products of a supervolcano similar in size and eruption rates to the Taupō and Yellowstone calderas. It may also represent the largest supervolcanic eruption of the Paleozoic era . Most of the volcanic rocks were laid down during a timespan of possibly less than two million years. A region of coarse co- ignimbritic breccias in the Flat Landing Brook Formation (Grants Lake pyroclastics)

1782-504: The extrusive equivalent of granite. However, while the IUGS recommends classifying volcanic rocks on the basis of their mineral composition whenever possible, volcanic rocks are often glassy or so fine-grained that mineral identification is impractical. The rock must then be classified chemically based on its content of silica and alkali metal oxides ( K 2 O plus Na 2 O ). Rhyolite is high in silica and total alkali metal oxides, placing it in

1836-624: The igneous rock is deposited on the surface of the earth in loose aggregate form. The material is mined by open-pit methods. Soils are removed by machinery in order to obtain more pure quality pumice. Scalping screens are used to filter impure surficial pumice of organic soils and unwanted rocks. Blasting is not necessary because the material is unconsolidated, therefore only simple machinery is used such as bulldozers and power shovels. Different sizes of pumice are needed for specific uses therefore crushers are used to achieve desired grades ranging from lump, coarse, intermediate, fine, and extra fine. Pumice

1890-616: The largest-known deep ocean volcanic eruption on Earth. The volcano erupted in July 2012 but remained unnoticed until enormous pieces of pumice were seen to be floating on the Pacific Ocean. Blankets of rock reached a thickness of 5 meters. Most of this floating pumice is deposited on the northwest coast of New Zealand and the Polynesia islands. The mining of pumice is an environmentally friendly process compared with other mining methods because

1944-490: The pet industry. The mining of pumice in environmentally sensitive areas has been under more scrutiny after such an operation was stopped in the U.S. state of Oregon, at Rock Mesa in the southern part of the Three Sisters Wilderness . Pumice has been used in the medicinal industry for more than 2000 years. Ancient Chinese medicine used ground pumice along with ground mica and fossilized bones added to teas to calm

1998-434: The rhyolite appears to be a product of melting of crustal sedimentary rock. Water vapor plays an important role in lowering the melting point of silicic rock, and some rhyolitic magmas may have a water content as high as 7–8 weight percent. High-silica rhyolite (HSR), with a silica content of 75 to 77·8% SiO 2 , forms a distinctive subgroup within the rhyolites. HSRs are the most evolved of all igneous rocks, with

2052-534: The second-most dangerous volcanic eruption in the 20th century, Mount Pinatubo , which erupted on June 12, 1991 in the Philippines . Ash and pumice lapilli were distributed over a mile around the volcano. These ejections filled trenches that once reached 660 feet deep. So much magma was displaced from the vent that the volcano became a depression on the surface of the Earth. Another well-known volcano that produces pumice

2106-434: The skin and cornea. Concoctions such as these were also used to help wounds scar in a supposedly healthier manner. In approximately 1680 it was noted by an English naturalist that pumice powder was used to promote sneezing. Pumice has been used as a material in personal care for thousands of years. It is an abrasive material that can be used in powdered form or as a stone to remove unwanted hair or skin. In ancient Egypt , it

2160-576: The soil due to volcanic activity. For example, in the Jemez Mountains of New Mexico, the Ancestral Puebloans settled on "pumice patches" of the El Cajete Pumice which likely retained a greater amount of moisture and was ideal for farming. Pumice is widely used to make lightweight concrete and insulative low-density cinder blocks . The air-filled vesicles in this porous rock serve as

2214-443: The spirit. This tea was used to treat dizziness, nausea, insomnia, and anxiety disorders. Ingestion of these pulverized rocks was believed to be able to soften nodules and was later used with other herbal ingredients to treat gallbladder cancer and urinary difficulties. In Western medicine, beginning in the early 18th century, pumice ground into a sugar consistency mixed with other ingredients was used to attempt to treat ulcers mostly on

Flat Landing Brook Formation - Misplaced Pages Continue

2268-561: The start of the 20th century: at the St. Andrew Strait volcano in Papua New Guinea and Novarupta volcano in Alaska as well as at Chaitén and Cordón Caulle volcanoes in southern Chile . The eruption of Novarupta in 1912 was the largest volcanic eruption of the 20th century, and began with explosive volcanism that later transitioned to effusive volcanism and the formation of a rhyolite dome in

2322-400: The surface. Pumice improves the quality of soil because of its porous properties; water and gases can be transported easily through the pores and nutrients can be stored in the microscopic holes. Pumice rock fragments are inorganic therefore no decomposition and little compaction occur. Another benefit of this inorganic rock is that it does not attract or host fungi or insects . As drainage

2376-450: The vent. Rhyolite magmas can be produced by igneous differentiation of a more mafic (silica-poor) magma, through fractional crystallization or by assimilation of melted crustal rock ( anatexis ). Associations of andesites , dacites , and rhyolites in similar tectonic settings and with similar chemistry suggests that the rhyolite members were formed by differentiation of mantle-derived basaltic magmas at shallow depths. In other cases,

2430-642: The way to rhyolite, and about 8% of the volcanic rock in Iceland is rhyolite. However, this is unusual, and the Hawaiian Islands (for example) have no known occurrences of rhyolite. The alkaline magmas of volcanic ocean islands will very occasionally differentiate all the way to peralkaline rhyolites, but differentiation usually ends with trachyte . Small volumes of rhyolite are sometimes erupted in association with flood basalts , late in their history and where central volcanic complexes develop. The name rhyolite

2484-416: Was also commonly used as a construction material for many aqueducts . One of the main uses of pumice currently in the United States is manufacturing concrete. This rock has been used in concrete mixtures for thousands of years and continues to be used in producing concrete, especially in regions close to where this volcanic material is deposited. New studies prove a broader application of pumice powder in

2538-408: Was called "lapis spongiae" in Latin for its vesicular properties. Many Greek scholars decided there were different sources of pumice, one of which was in the sea coral category. Pumice can be found all around the globe deriving from continental volcanic occurrences and submarine volcanic occurrences. Floating stones can also be distributed by ocean currents. As described earlier pumice is produced by

2592-407: Was common to remove all hair on the body to control lice and as a form of ritual purification, using creams, razors, and pumice stones. Pumice in powdered form was an ingredient in toothpastes in ancient Rome. Nail care was very important in ancient China; nails were kept groomed with pumice stones, and pumice stones were also used to remove calluses. It was discovered in a Roman poem that pumice

2646-563: Was erupted caused the structure to collapse, forming a caldera now known as Crater Lake . Chile is one of the leading producers of pumice in the world. The Puyehue-Cordón Caulle are two coalesced volcanoes in the Andes mountains that ejected ash and pumice across Chile and Argentina . A recent eruption in 2011 wreaked havoc on the region by covering all surfaces and lakes in ash and pumice. Kenya , Ethiopia and Tanzania have some deposits of pumice. The Havre Seamount volcano produced

2700-558: Was estimated at 17 million tonnes. There are large reserves of pumice in Asian countries including Afghanistan, Indonesia, Japan, Syria, Iran, and eastern Russia. Considerable amounts of pumice can be found at the Kamchatka Peninsula on the eastern flank of Russia. This area contains 19 active volcanoes and it lies in close proximity with the Pacific volcanic belt . Asia is also the site of

2754-465: Was estimated at 380,000 tonnes, valued at $ 7.7 million with approximately 46% coming from Nevada and Oregon. Idaho is also known as a large producer of pumice because of the quality and brightness of the rock found in local reserves. One of the most famous volcanoes was Mount Mazama that erupted 7,700 years ago in Oregon and deposited 300 feet of pumice and ash around the vent. The large amount of magma that

SECTION 50

#1732855873609

2808-630: Was introduced into geology in 1860 by the German traveler and geologist Ferdinand von Richthofen from the Greek word rhýax ("a stream of lava") and the rock name suffix "-lite". In North American pre-historic times , rhyolite was quarried extensively in what is now eastern Pennsylvania . Among the leading quarries was the Carbaugh Run Rhyolite Quarry Site in Adams County . Rhyolite

2862-559: Was mined there starting 11,500 years ago. Tons of rhyolite were traded across the Delmarva Peninsula , because the rhyolite kept a sharp point when knapped and was used to make spear points and arrowheads. Obsidian is usually of rhyolitic composition, and it has been used for tools since prehistoric times. Obsidian scalpels have been investigated for use in delicate surgery. Pumice, also typically of rhyolitic composition, finds important uses as an abrasive , in concrete , and as

2916-486: Was used to remove dead skin as far back as 100 BC, and likely before then. It has been used throughout many eras since then, including the Victorian Era . Today, many of these techniques are still used; pumice is widely used as a skin exfoliant . Even though hair removal techniques have evolved over the centuries, abrasive material like pumice stones is also still used. "Pumice stones" are often used in beauty salons during

#608391