Pumice

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Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. Density of specimen approximately 0.25 g/cm ; scale in centimeters. Teidepumice.jpg
Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. Density of specimen approximately 0.25 g/cm ; scale in centimeters.
Kutkhiny Baty, a pumice rock formation outcrop located 4 km from the source of the Ozernaya River (Lake Kurile), near the southern tip of the Kamchatka Peninsula, Russia. Kuthiny Baty.jpg
Kutkhiny Baty, a pumice rock formation outcrop located 4 km from the source of the Ozernaya River (Lake Kurile), near the southern tip of the Kamchatka Peninsula, Russia.

Pumice ( /ˈpʌmɪs/ ), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly 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. [1] [2]

Contents

Pumice is created when super-heated, highly pressurized rock is violently ejected from 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 CO2) that are dissolved in the lava, causing the gases to rapidly exsolve (like the bubbles of CO2 that appear when a carbonated drink is opened). The simultaneous cooling and depressurization freezes 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. [3] . The pores of pumice and pumicite can have sizes from a wide range. Namely, the size of the pores can be as large as parts of micrometre (μm) and more rough pores with sizes up to 2-3 mm. The main difference between pumice and the pumicite is in the size of the grains. More specifically, the material with grain size of 2 mm or larger (up to large blocks) is classified as pumice. On the other hand, the material with size of grains smaller than 2 mm (including the fine dispersed material) is classified as pumicite. [4]

Properties

Pumice is composed of highly microvesicular glass pyroclastic with very thin, translucent bubble walls of extrusive igneous rock. It is commonly [5] 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 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 is eventually waterlogged and sinks. [6]

Scoria differs from pumice in being denser. With larger vesicles and thicker vesicle walls, scoria sinks rapidly. The difference 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. 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 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. [7] In fact, pumice rafts disperse and support several marine species. [8] In 1979, 1984 and 2006, underwater volcanic eruptions near Tonga created large pumice rafts, some as large as 30 kilometers (19 mi)[ citation needed ] that floated hundreds of kilometres to Fiji. [9]

There are two main forms of vesicles. Most pumice contains tubular microvesicles that can impart 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 eruption.

Etymology

Pumice is igneous rock with a foamy appearance. The name is derived from the Latin word "pumex" which means "foam" and through history has been given many names because its formation was unclear. In former times it was called "Spuma Maris", meaning froth of the sea in Latin, because it was a frothy material thought to be hardened sea foam. It was also known as "écume de mer" in French and “Meerschaum” in German for the same reason. Around 80 B.C., it 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. [10]

Location

Pumice can be found all around the globe deriving from continental volcanic occurrence and submarine volcanic occurrence. Floating stones can also be distributed by ocean currents. [11] As described earlier pumice is produced by 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 tonnes respectively; other large producers at or exceeding a million tonnes were Greece, Iran, Chile and Syria. Total world pumice production in 2011 was estimated at 17 million tonnes. [12]

Asia

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 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 than the volcano became a depression on the surface of the Earth. [13] Another well-known volcano that produces pumice 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. [14]

Europe

Europe is the largest producer of pumice with deposits in Italy, Turkey, Greece, Hungary and Iceland. Italy is the largest producer of pumice because of its numerous eruptive volcanoes. On the Aeolian Islands of Italy, the island of Lipari 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. [15]

North America

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 was estimated at 380,000 tonnes, valued at $7.7 million with approximately 46% coming from Nevada and Oregon. [12] Idaho is also known as a large producer of pumice because of the quality and brightness of the rock found in local reserves. [16] One of the most famous volcanoes was Mount Mazama that erupted 7,700 years ago in Oregon and depostied 300 feet of pumice and ash around the vent. The large amount of magma that was erupted caused the structure to collapse, forming a caldera now known as Crater Lake. [13]

South America

Chile is one of the leading producers of pumice in the world. [17] 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. [18]

Africa

Kenya, Ethiopia and Tanzania have some deposits of pumice. [11]

New Zealand

The Havre Seamount volcano produced 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. [19] Most of this floating pumice is deposited on the North-West coast of New Zealand and the Polynesia islands.

Mining

The mining of pumice is an environmentally friendly process compared with other mining methods because 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. [20]

Uses

Pumice is a very light weight, 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. [21] There is high demand for pumice, particularly for water filtration, chemical spill containment, cement manufacturing [22] , horticulture and increasingly for 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. [23]

Early medicine

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 the spirit. This tea was used to treat dizziness, nausea, insomnia, and anxiety disorders. Ingestion of these pulverized rocks were actually 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 was ground into a sugar consistency and with other ingredients was used to treat ulcers mostly on the skin and cornea. Concoctions such as these were also used to help wounds scar in a healthier manner. In approximately 1680 it was noted by an English naturalist that pumice powder was used to promote sneezing. [24]

Personal care

Pumice soap bars Puimsteenzeep.png
Pumice soap bars

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 skincare and beauty were very important to all classes and makeup and moisturizers were widely used. One common trend was to remove all hair on the body using creams, razors and pumice stones. Pumice in powdered form was used to whiten teeth in ancient Rome.[ citation needed ] Nail care was very important in ancient China; nails were kept groomed with pumice stones and to remove calluses. It was discovered in a roman poem that pumice was used to remove dead skin as far back as 100 BC and likely before then. [25] 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. Hair removal techniques have evolved over the centuries, however abrasive material like pumice stones are still used. "Pumice stones" are often used in beauty salons during the pedicure process to remove dry and excess skin from the bottom of the foot as well as calluses. If pumice stones are not being used in current nail care there are substitutes such as skin and nail specific sandpaper or steel files. Finely ground pumice is added to some toothpastes as a whitener, similar to Roman use, and easily removes dental plaque build up. 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.

Horticulture

A 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 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 occurs. Another benefit of this inorganic rock is that it does not attract or host fungi or insects. Drainage 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. Addition of pumice to a soil improves and increases vegetative cover as the roots of plants make slopes more stable therefore it helps reduce erosion. It 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. With regards to chemical properties pumice is pH neutral, it is not acidic or alkaline. [26] In 2011, 16% of pumice mined in the United States was used for horticultural purposes. [12]

Construction

Pumice is widely used to make lightweight concrete and insulative low-density cinder blocks. The air filled vesicles in this porous rock serves as a good insulator. [13] 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 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. [27] New studies prove a broader application of pumice powder in the concrete industry. Pumice can act as a cementitious material in concrete and researchers have shown that concrete made with up to 50% pumice powder can significantly improve durability yet reduce the greenhouse gas emissions and fossil fuel consumption. [22]

See also

Related Research Articles

Basalt A magnesium- and iron-rich extrusive igneous rock

Basalt is a mafic extrusive igneous rock formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. More than 90% of all volcanic rock on Earth is basalt. Basalt lava has a low viscosity, due to its low silica content, resulting in rapid lava flows that can spread over great areas before cooling and solidification. Flood basalt describes the formation in a series of lava basalt flows.

Tuff Rock consolidated from volcanic ash

Tuff, also known as volcanic tuff, is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is compacted into a solid rock in a process called consolidation. Tuff is sometimes erroneously called "tufa", particularly when used as construction material, but geologically tufa is a limestone precipitated from groundwater. Rock that contains greater than 50% tuff is considered tuffaceous.

Volcanic cone Landform of ejecta from a volcanic vent piled up in a conical shape

Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types of volcanic cones include stratocones, spatter cones, tuff cones, and cinder cones.

Extrusive rock

Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In contrast, intrusive rock refers to rocks formed by magma which cools below the surface.

Volcanic rock Volcanic rocks composing or associated with volcanoes, volcanic activity or volcanism

Volcanic rock is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct. In the context of Precambrian shield geology, the term "volcanic" is often applied to what are strictly metavolcanic rocks. Volcanic rocks and sediment that form from magma erupted into the air are called "volcaniclastics," and these are technically sedimentary rocks.

Pyroclastic rock Clastic rocks composed solely or primarily of volcanic materials

Pyroclastic rocks or pyroclastics are sedimentary clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic. Commonly associated with unsieved volcanic activity—such as Plinian or krakatoan eruption styles, or phreatomagmatic eruptions—pyroclastic deposits are commonly formed from airborne ash, lapilli and bombs or blocks ejected from the volcano itself, mixed in with shattered country rock. Tephra is any sized material formed by a volcanic eruption.

Magma chamber Accumulation of molten rock within the Earths crust

A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is under great pressure. Given enough time, that pressure can gradually fracture the rock around it, creating a way for the magma to move upward. If it finds its way to the surface, then the result will be a volcanic eruption; consequently, many volcanoes are situated over magma chambers. These chambers are hard to detect deep within the Earth, and therefore most of those known are close to the surface, commonly between 1 km and 10 km down.

Ignimbrite A variety of hardened tuff

Ignimbrite is a variety of hardened tuff. Ignimbrites are igneous rocks made up of crystal and rock fragments in a glass-shard groundmass, albeit the original texture of the groundmass might be obliterated due to high degrees of welding. The term ignimbrite is not recommended by the IUGS Subcommission on the Systematics of Igneous Rocks.

Scoria Dark vesicular volcanic rock

Scoria is a highly vesicular, dark colored volcanic rock that may or may not contain crystals (phenocrysts). It is typically dark in color, and basaltic or andesitic in composition. Scoria is relatively low in density as a result of its numerous macroscopic ellipsoidal vesicles, but in contrast to pumice, all scoria has a specific gravity greater than 1, and sinks in water. The holes or vesicles form when gases that were dissolved in the magma come out of solution as it erupts, creating bubbles in the molten rock, some of which are frozen in place as the rock cools and solidifies. Scoria may form as part of a lava flow, typically near its surface, or as fragmental ejecta, for instance in Strombolian eruptions that form steep-sided scoria cones. Chemical analysis of scoria found in Yemen showed that it was mainly composed of volcanic glass with a few zeolites. Most scoria is composed of glassy fragments, and may contain phenocrysts. The word scoria comes from the Greek σκωρία, skōria, rust. A colloquial term for scoria is cinder.

Cinder Pyroclastic vesicular rock

A cinder is a pyroclastic material. Cinders are extrusive igneous rocks; they are fragments of solidified lava. Cinders are typically brown, black, or red depending on chemical composition and weathering. Cinders are similar to pumice.

Vesicular texture

Vesicular texture is a volcanic rock texture characterized by a rock being pitted with many cavities at its surface and inside. This texture is common in aphanitic, or glassy, igneous rocks that have come to the surface of the earth, a process known as extrusion. As magma rises to the surface the pressure on it decreases. When this happens gasses dissolved in the magma are able to come out of solution, forming gas bubbles inside it. When the magma finally reaches the surface as lava and cools, the rock solidifies around the gas bubbles and traps them inside, preserving them as holes filled with gas called vesicles.

Types of volcanic eruptions Basic mechanisms of eruption and variations

Several types of volcanic eruptions—during which lava, tephra, and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series.

Panum Crater mountain in United States of America

Panum Crater is a volcanic cone that is part of the Mono–Inyo Craters, a chain of recent volcanic cones south of Mono Lake and east of the Sierra Nevada, in California, United States. Panum Crater is between 600 and 700 years old, and it exhibits all of the characteristics of the textbook rhyolitic lava dome.

Dense-rock equivalent is a volcanologic calculation used to estimate volcanic eruption volume. One of the widely accepted measures of the size of a historic or prehistoric eruption is the volume of magma ejected as pumice and volcanic ash, known as tephra during an explosive phase of the eruption, or the volume of lava extruded during an effusive phase of a volcanic eruption. Eruption volumes are commonly expressed in cubic kilometers (km3).

Mount Edziza volcanic complex mountain in Canada

The Mount Edziza volcanic complex is a large and potentially active north-south trending complex volcano in Stikine Country, northwestern British Columbia, Canada, located 38 kilometres (24 mi) southeast of the small community of Telegraph Creek. It occupies the southeastern portion of the Tahltan Highland, an upland area of plateau and lower mountain ranges, lying east of the Boundary Ranges and south of the Inklin River, which is the east fork of the Taku River. As a volcanic complex, it consists of many types of volcanoes, including shield volcanoes, calderas, lava domes, stratovolcanoes, and cinder cones.

Volcanology of Mars

Volcanic activity, or volcanism, has played a significant role in the geologic evolution of Mars. Scientists have known since the Mariner 9 mission in 1972 that volcanic features cover large portions of the Martian surface. These features include extensive lava flows, vast lava plains, and the largest known volcanoes in the Solar System. Martian volcanic features range in age from Noachian to late Amazonian, indicating that the planet has been volcanically active throughout its history, and some speculate it probably still is so today. Both Earth and Mars are large, differentiated planets built from similar chondritic materials. Many of the same magmatic processes that occur on Earth also occurred on Mars, and both planets are similar enough compositionally that the same names can be applied to their igneous rocks and minerals.

Lava Molten rock expelled by a volcano during an eruption

Lava is molten rock generated by geothermal energy and expelled through fractures in planetary crust or in an eruption, usually at temperatures from 700 to 1,200 °C. The structures resulting from subsequent solidification and cooling are also sometimes described as lava. The molten rock is formed in the interior of some planets, including Earth, and some of their satellites, though such material located below the crust is referred to by other terms.

Tectonic–climatic interaction is the interrelationship between tectonic processes and the climate system. The tectonic processes in question include orogenesis, volcanism, and erosion, while relevant climatic processes include atmospheric circulation, orographic lift, monsoon circulation and the rain shadow effect. As the geological record of past climate changes over millions of years is sparse and poorly resolved, many questions remain unresolved regarding the nature of tectonic-climate interaction, although it is an area of active research by geologists and palaeoclimatologists.

Volcanic ash volcanic material formed during explosive eruptions with the diameter of the grains less than 2 mm

Volcanic ash consists of fragments of rock, minerals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products, including particles larger than 2 mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the gasses shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometres away.

Lava balloon Floating bubble of lava

A lava balloon is a gas-filled bubble of lava that floats on the sea surface. It can be up to several metres in size. When it emerges from the sea, it is usually hot and often steaming. After floating for some time it fills with water and sinks again.

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