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123-589: Mayon ( Central Bikol : Bulkan Mayon ; Tagalog : Bulkang Mayon , IPA: [mɐ'jɔn] ), also known as Mount Mayon and Mayon Volcano ( Spanish : Monte Mayón, Volcán Mayón ), is an active stratovolcano in the province of Albay in Bicol , Philippines. A popular tourist spot, it is renowned for its "perfect cone" because of its symmetric conical shape , and is regarded as sacred in Philippine mythology . The volcano with its surrounding landscape

246-494: A Thai national who was unable to walk due to fatigue and had suffered a broken arm and burns on the neck and back. Despite the eruption, the Philippine Institute of Volcanology and Seismology stated that the alert level would remain at 0. No volcanic earthquake activity was detected in the 24 hours prior to the eruption as no indication of further intensification of volcanic activity was observed, and no evacuation

369-454: A hyperbolic sine curve of the volcano is due to the balance between erosion and eruption , defined by the angle of repose of ash . The steepest upper slopes of the volcano reach an average slope gradient of 75%, while the lower foot slope is only an average of 3%. The volcanic crater is about 250 m in diameter. At least 85 lava flows have been identified, and consist mainly of lava augite - hypersthene -andesite, generally fed from

492-505: A reflexive verb . The lower plate itself is the subject. It subducts, in the sense of retreat, or removes itself, and while doing so, is the "subducting plate". Moreover, the word slab is specifically attached to the "subducting plate", even though in English the upper plate is just as much of a slab. The upper plate is left hanging, so to speak. To express it geology must switch to a different verb, typically to override . The upper plate,

615-608: A bright glow signifying the growth of a new lava dome and the start of lava flows towards its slopes. Central Bikol language Central Bikol features some vocabulary not found in other Bikol languages nor in other members of the Central Philippine language family like Tagalog and Cebuano . Examples are the words matua and bitis , which are the same as the Kapampangan words meaning 'older' and 'foot, feet', respectively. The word banggi ('night')

738-460: A larger portion of Earth's crust to deform in a more brittle fashion than it would in a normal geothermal gradient setting. Because earthquakes can occur only when a rock is deforming in a brittle fashion, subduction zones can cause large earthquakes. If such a quake causes rapid deformation of the sea floor, there is potential for tsunamis . The largest tsunami ever recorded happened due to a mega-thrust earthquake on December 26, 2004 . The earthquake

861-457: A minimum estimate of how far the continent has subducted. The results show at least a minimum of 229 kilometers of subduction of the northern Australian continental plate. Another example may be the continued northward motion of India, which is subducting beneath Asia. The collision between the two continents initiated around 50 my ago, but is still active. Oceanic-Oceanic plate subduction zones comprise roughly 40% of all subduction zone margins on

984-587: A number of loanwords, largely Spanish ones as a result of Spanish rule in the Philippines. These include swerte ( suerte , 'luck'), karne ( carne , 'meat'), imbestigador ( investigador , 'investigator'), litro ('liter'), pero ('but'), and krimen ( crimen , 'crime'). Another source of loanwords in Bikol is Sanskrit , with examples including words like bahala ('responsibility') and karma . There are 16 consonants in

1107-469: A point of no return. Sections of crustal or intraoceanic arc crust greater than 15 km (9.3 mi) in thickness or oceanic plateau greater than 30 km (19 mi) in thickness can disrupt subduction. However, island arcs subducted end-on may cause only local disruption, while an arc arriving parallel to the zone can shut it down. This has happened with the Ontong Java Plateau and

1230-532: A rich set of discourse particles. There exist two types of numerals in Bikol: native Bikol and Spanish numerals. Generally, Bicolanos use the Spanish terms when referring to time, as in the phrase a las singko ('5 o'clock'). However, the native terms can be read in literary books. The Spanish numerals are often encountered in pricing. The angry register of Bikol, also known natively as tamanggot or rapsak ,

1353-510: A zone of shortening and crustal thickening in which there may be extensive folding and thrust faulting . If the angle of subduction steepens or rolls back, the upper plate lithosphere will be put in tension instead, often producing a back-arc basin . The arc-trench complex is the surface expression of a much deeper structure. Though not directly accessible, the deeper portions can be studied using geophysics and geochemistry . Subduction zones are defined by an inclined zone of earthquakes ,

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1476-443: Is geographically shared by the eight cities and municipalities of Legazpi , Daraga , Camalig , Guinobatan , Ligao , Tabaco , Malilipot , and Santo Domingo (clockwise from Legazpi), which divide the cone like slices of a pie when viewing a map of their political boundaries. Mayon is a classic stratovolcano with a small central summit crater . It is one of the world's most symmetrical volcanic cones. The concave profile ,

1599-418: Is "consumed", which happens the geological moment the lower plate slips under, even though it may persist for some time until its remelting and dissipation. In this conceptual model, plate is continually being used up. The identity of the subject, the consumer, or agent of consumption, is left unstated. Some sources accept this subject-object construct. Geology makes to subduct into an intransitive verb and

1722-499: Is accreted to (scraped off) the continent, resulting in exotic terranes . The collision of this oceanic material causes crustal thickening and mountain-building. The accreted material is often referred to as an accretionary wedge or prism. These accretionary wedges can be associated with ophiolites (uplifted ocean crust consisting of sediments, pillow basalts, sheeted dykes, gabbro, and peridotite). Subduction may also cause orogeny without bringing in oceanic material that accretes to

1845-960: Is another example of this as it is different from the usual Bikol word gab-i but closer to the word bengi of Kapampangan. There is no formal study on the relationship of the Central Luzon languages to Central Bikol but the latter has several words that are also found in the archaic form of Tagalog spoken in the Rizal and Quezon provinces that are believed to be the home of Central Luzon languages such as Kapampangan in Pampanga and southern Tarlac , and Sambalic languages in Zambales province. Because of its broad geographic coverage as compared to other Bikol languages separated by islands and mountains, Central Bikol diverged into six dialects, which are still mutually comprehensible. The division of

1968-465: Is broken into sixteen larger tectonic plates and several smaller plates. These plates are in slow motion, due mostly to the pull force of subducting lithosphere. Sinking lithosphere at subduction zones are a part of convection cells in the underlying ductile mantle . This process of convection allows heat generated by radioactive decay to escape from the Earth's interior. The lithosphere consists of

2091-496: Is characterized by low geothermal gradients and the associated formation of high-pressure low-temperature rocks such as eclogite and blueschist . Likewise, rock assemblages called ophiolites , associated with modern-style subduction, also indicate such conditions. Eclogite xenoliths found in the North China Craton provide evidence that modern-style subduction occurred at least as early as 1.8  Ga ago in

2214-403: Is driven by the temperature difference between the slab and the surrounding asthenosphere, as the colder oceanic lithosphere is, on average, more dense. Sediments and some trapped water are carried downwards by the slab and recycled into the deep mantle. Earth is so far the only planet where subduction is known to occur, and subduction zones are its most important tectonic feature. Subduction

2337-444: Is fairly well understood, the process by which subduction is initiated remains a matter of discussion and continuing study. Subduction can begin spontaneously if the denser oceanic lithosphere can founder and sink beneath the adjacent oceanic or continental lithosphere through vertical forcing only; alternatively, existing plate motions can induce new subduction zones by horizontally forcing the oceanic lithosphere to rupture and sink into

2460-614: Is found behind the Aleutian Trench subduction zone in Alaska. Volcanoes that occur above subduction zones, such as Mount St. Helens , Mount Etna , and Mount Fuji , lie approximately one hundred kilometers from the trench in arcuate chains called volcanic arcs . Plutons, like Half Dome in Yosemite National Park, generally form 10–50 km below the volcanoes within the volcanic arcs and are only visible on

2583-477: Is more buoyant and as a result will rise into the lithosphere, where it forms large magma chambers called diapirs. Some of the magma will make it to the surface of the crust where it will form volcanoes and, if eruptive on earth's surface, will produce andesitic lava. Magma that remains in the lithosphere long enough will cool and form plutonic rocks such as diorite, granodiorite, and sometimes granite. The arc magmatism occurs one hundred to two hundred kilometers from

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2706-411: Is old, goes down the subduction zone. As this happens, metamorphic reactions increase the density of the continental crustal rocks, which leads to less buoyancy. One study of the active Banda arc-continent collision claims that by unstacking the layers of rock that once covered the continental basement, but are now thrust over one another in the orogenic wedge, and measuring how long they are, can provide

2829-723: Is ongoing beneath part of the Andes , causing segmentation of the Andean Volcanic Belt into four zones. The flat-slab subduction in northern Peru and the Norte Chico region of Chile is believed to be the result of the subduction of two buoyant aseismic ridges, the Nazca Ridge and the Juan Fernández Ridge , respectively. Around Taitao Peninsula flat-slab subduction is attributed to the subduction of

2952-426: Is possible because the cold and rigid oceanic lithosphere is slightly denser than the underlying asthenosphere , the hot, ductile layer in the upper mantle . Once initiated, stable subduction is driven mostly by the negative buoyancy of the dense subducting lithosphere. The down-going slab sinks into the mantle largely under its own weight. Earthquakes are common along subduction zones, and fluids released by

3075-529: Is spoken in the eastern coast of Albay and the northeastern part of Sorsogon. TLS is the dialect that has been most influenced by the Inland Bikol languages . The Daet dialect, on the other hand, is spoken in the second district of the province of Camarines Norte. The Virac dialect (or Viracnon language) is spoken around Virac, Catanduanes and surrounding towns on the southeastern part of the island of Catanduanes. Like other Philippine languages , Bikol has

3198-404: Is the driving force behind plate tectonics , and without it, plate tectonics could not occur. Oceanic subduction zones are located along 55,000 km (34,000 mi) convergent plate margins, almost equal to the cumulative plate formation rate 60,000 km (37,000 mi) of mid-ocean ridges. Sea water seeps into oceanic lithosphere through fractures and pores, and reacts with minerals in

3321-426: Is the most active volcano in the Philippines , erupting over 52 times in the past 500 years. Historical observations accounted its first eruption in 1616. The first eruption for which an extended account exists was the six-day event of July 20, 1766. Its most destructive recorded eruption occurred on February 1 ( VEI =4). Lava flowed but less than the 1766 eruption. The volcano belched dark ash and eventually bombarded

3444-463: Is used when angry, shouting, or speaking in a high-pitched voice at someone. Some examples of the register include: Note: Subduction zone Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second plate,

3567-758: The Bicol Arc is related to the westward subduction of the Philippine Plate along the Philippine Trench . The 12 active and inactive volcanoes within the arc include the Mayon Volcano, Mount Bulusan , Mount Isarog , Mount Iriga , Malinao Volcano , and Mount Masaraga . In general, these are calc-alkali basalts , basaltic andesites, and andesites . In August 2021, soils from Mayon have been found containing bacterial species with potential antibiotic and anti-cancer properties. Mayon

3690-528: The Cascade Volcanic Arc , that form along the coast of continents. Island arcs (intraoceanic or primitive arcs) are produced by the subduction of oceanic lithosphere beneath another oceanic lithosphere (ocean-ocean subduction) while continental arcs (Andean arcs) form during the subduction of oceanic lithosphere beneath a continental lithosphere (ocean-continent subduction). An example of a volcanic arc having both island and continental arc sections

3813-774: The Chile Rise , a spreading ridge . The Laramide Orogeny in the Rocky Mountains of the United States is attributed to flat-slab subduction. During this orogeny, a broad volcanic gap appeared at the southwestern margin of North America, and deformation occurred much farther inland; it was during this time that the basement -cored mountain ranges of Colorado, Utah, Wyoming, South Dakota, and New Mexico came into being. The most massive subduction zone earthquakes, so-called "megaquakes", have been found to occur in flat-slab subduction zones. Although stable subduction

Mayon - Misplaced Pages Continue

3936-630: The Paleoproterozoic Era . The eclogite itself was produced by oceanic subduction during the assembly of supercontinents at about 1.9–2.0 Ga. Blueschist is a rock typical for present-day subduction settings. The absence of blueschist older than Neoproterozoic reflects more magnesium-rich compositions of Earth's oceanic crust during that period. These more magnesium-rich rocks metamorphose into greenschist at conditions when modern oceanic crust rocks metamorphose into blueschist. The ancient magnesium-rich rocks mean that Earth's mantle

4059-414: The Philippine Institute of Volcanology and Seismology (PHIVOLCS) from their provincial headquarters on Ligñon Hill , about 12 kilometers (7.5 mi) from the summit. Mayon is the main landmark and highest point of the province of Albay and the whole Bicol Region in the Philippines, rising 2,463 meters (8,081 ft) from the shores of Albay Gulf about 10 kilometers (6.2 mi) away. The volcano

4182-491: The Vitiaz Trench . Subduction zones host a unique variety of rock types created by the high-pressure, low-temperature conditions a subducting slab encounters during its descent. The metamorphic conditions the slab passes through in this process create and destroy water bearing (hydrous) mineral phases, releasing water into the mantle. This water lowers the melting point of mantle rock, initiating melting. Understanding

4305-533: The Wadati–Benioff zone , that dips away from the trench and extends down below the volcanic arc to the 660-kilometer discontinuity . Subduction zone earthquakes occur at greater depths (up to 600 km (370 mi)) than elsewhere on Earth (typically less than 20 km (12 mi) depth); such deep earthquakes may be driven by deep phase transformations , thermal runaway , or dehydration embrittlement . Seismic tomography shows that some slabs can penetrate

4428-406: The core–mantle boundary . Here the slabs are heated up by the ambient heat and are not detected anymore ~300 Myr after subduction. Orogeny is the process of mountain building. Subducting plates can lead to orogeny by bringing oceanic islands, oceanic plateaus, sediments and passive continental margins to convergent margins. The material often does not subduct with the rest of the plate but instead

4551-411: The lower mantle and sink clear to the core–mantle boundary . Here the residue of the slabs may eventually heat enough to rise back to the surface as mantle plumes . Subduction typically occurs at a moderately steep angle by the time it is beneath the volcanic arc. However, anomalous shallower angles of subduction are known to exist as well as some that are extremely steep. Flat-slab subduction

4674-416: The zeolite , prehnite-pumpellyite, blueschist , and eclogite facies stability zones of subducted oceanic crust. Zeolite and prehnite-pumpellyite facies assemblages may or may not be present, thus the onset of metamorphism may only be marked by blueschist facies conditions. Subducting slabs are composed of basaltic crust topped with pelagic sediments ; however, the pelagic sediments may be accreted onto

4797-590: The 1984 eruption after more than 73,000 people were evacuated from the danger zones as recommended by PHIVOLCS scientists. But in 1993, pyroclastic flows killed 79 people, mainly farmers, during the eruption that also forced 50,000 residents evacuated, according to the Albay provincial government. Mayon began its increasing activity in May, with hazard status associated raised to Alert Level 1. On June 22, Mayon emitted an ash column that rose to approximately 10 km above

4920-486: The 2000 eruption displaced 14,114 families (68,426 persons) and damaged at least ₱89-million worth of property and crops. The NDCC reported that another eruption in July affected 11,529 families (56,853 persons) and damaged at least ₱48-million worth of property and crops. Mayon's 48th modern-era eruption occurred on July 13, followed by quiet effusion of lava that started on July 14. Nearly 40,000 people were evacuated from

5043-497: The 4–6 km danger zone remained in the evacuation centers pending a decision to further lower the alert level. On January 13, PHIVOLCS reduced the Alert Level from 3 to 2 due to a further reduction in the likelihood of hazardous eruption. Albay governor Joey Salceda declared the disaster zone an 'open city' area to encourage aid from external groups. Potential donors of relief goods were not required to secure clearance from

Mayon - Misplaced Pages Continue

5166-434: The 8-kilometre (5.0 mi) danger zone on the southeast flank of the volcano . After an ash explosion on September 1, a general decline in the overall activity of Mayon was established. The decrease in key parameters such as seismicity, sulfur dioxide emission rates and ground inflation all indicated a waning condition. The slowdown in the eruptive activity was also evident from the decrease in intensity of crater glow and

5289-506: The Alaskan crust. The concept of subduction would play a role in the development of the plate tectonics theory. First geologic attestations of the "subduct" words date to 1970, In ordinary English to subduct , or to subduce (from Latin subducere , "to lead away") are transitive verbs requiring a subject to perform an action on an object not itself, here the lower plate, which has then been subducted ("removed"). The geological term

5412-588: The Alps. The chemistry of the inclusions supports the existence of a carbon-rich fluid in that environment, and additional chemical measurements of lower pressure and temperature facies in the same tectonic complex support a model for carbon dissolution (rather than decarbonation) as a means of carbon transport. Elastic strain caused by plate convergence in subduction zones produces at least three types of earthquakes. These are deep earthquakes, megathrust earthquakes, and outer rise earthquakes. Deep earthquakes happen within

5535-529: The Bikol language: /m, n, ŋ, p, t, k, ʔ, b, d, ɡ, s, h, l, w~ʋ, ɾ, j~ʝ/ . Eight sounds are borrowed from loanwords: /f, v, ɲ, tʃ, dʒ, ʃ, ʒ, ʎ/ . The sound system of the language according to Mintz in 1971 is as follows. Native words exhibit a three-vowel system whose vowels can be noted as /a, i, u/ , with /u/ realized as [o] in the final syllable. Due to contact with Spanish, modern Central Bikol also has two marginal phonemes /e, o/ distinct from /i, u/ . Like many other Philippine languages , Bikol has

5658-523: The Provincial Disaster Coordinating Council, and were coordinated directly with support groups at the local government level. The restiveness of the volcano also stimulated the tourism industry of the province. Up to 2,400 tourists per day arrived in the area in the two weeks after the volcano started erupting on December 14, filling local hotels, compared to a more modest average of 200 in the days prior. However, it

5781-492: The accumulation of atmospheric ash together with the catastrophic 1815 eruption of other volcanoes like Indonesia's Mount Tambora , leading to the Year Without a Summer in 1816. From July 6, 1881, until approximately August 1882, Mayon underwent a strong (VEI=3) eruption. Samuel Kneeland , a naturalist , professor and geologist, personally observed the volcanic activity on Christmas Day, 1881, about five months after

5904-436: The alert level of the volcano from level 4 to level 3, citing decreasing activity observed over the prior four days. The state agency noted the absence of ash ejections and relative weakness of steam emissions and the gradual decrease in sulfur dioxide emissions from a maximum of 8,993 tonnes per day to 2,621 tonnes per day. 7,218 families within the 7–8 km danger zones returned to their homes, while 2,728 families residing in

6027-472: The asthenosphere. Both models can eventually yield self-sustaining subduction zones, as the oceanic crust is metamorphosed at great depth and becomes denser than the surrounding mantle rocks. The compilation of subduction zone initiation events back to 100 Ma suggests horizontally-forced subduction zone initiation for most modern subduction zones, which is supported by results from numerical models and geologic studies. Some analogue modeling shows, however,

6150-510: The asthenosphere. Individual plates often include both regions of the oceanic lithosphere and continental lithosphere. Subduction zones are where cold oceanic lithosphere sinks back into the mantle and is recycled. They are found at convergent plate boundaries, where the heavier oceanic lithosphere of one plate is overridden by the leading edge of another, less-dense plate. The overridden plate (the slab ) sinks at an angle most commonly between 25 and 75 degrees to Earth's surface. This sinking

6273-435: The continent, away from the trench, and has been described in western North America (i.e. Laramide orogeny, and currently in Alaska, South America, and East Asia. The processes described above allow subduction to continue while mountain building happens concurrently, which is in contrast to continent-continent collision orogeny, which often leads to the termination of subduction. Continents are pulled into subduction zones by

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6396-575: The crater and drifted northeast. In the prior 24 hours, 13 volcanic earthquakes were recorded. Steam emission was at moderate level, creeping downslope toward the southwest. PHIVOLCS maintained the Alert Status at Level 2, but later warned that with the approach of tropical cyclone international codename Mirinae, the danger of lahars and possible crater wall collapse would greatly increase and all specified precautions should be taken. After dawn, field investigation showed ashfall had drifted southwest of

6519-421: The crater. Pyroclastic flows , characterized as a St. Vincent nuee' ardente, leave behind block and ash deposits, and breadcrust bombs in an ash and lapilli matrix . The farthest flow reached 8.5 km along Fidel Surtida, Santo Domingo . Mayon lahars were formed by rainstorms during eruptions, or by torrential rain afterwards. Averaging 230 m in height and 710 m in diameter, 7 cinder cones are found on

6642-412: The crevices, and, as it passed beyond the line of complete vision behind the woods near the base, the fires twinkled like stars or the scintillations of a dying conflagration. More than half of the mountain height was thus illuminated. Mayon's longest uninterrupted eruption occurred on June 23 ( VEI =4), and lasted for seven days. Lava once again flowed down to towns eleven kilometers (6.8 miles) eastward,

6765-506: The crust and mantle to form hydrous minerals (such as serpentine) that store water in their crystal structures. Water is transported into the deep mantle via hydrous minerals in subducting slabs. During subduction, a series of minerals in these slabs such as serpentine can be stable at different pressures within the slab geotherms, and may transport significant amount of water into the Earth's interior. As plates sink and heat up, released fluids can trigger seismicity and induce melting within

6888-579: The crust would be melted and recycled into the Earth's mantle . In 1964, George Plafker researched the Good Friday earthquake in Alaska . He concluded that the cause of the earthquake was a megathrust reaction in the Aleutian Trench , a result of the Alaskan continental crust overlapping the Pacific oceanic crust. This meant that the Pacific crust was being forced downward, or subducted , beneath

7011-597: The crust, megathrust earthquakes on the subduction interface near the trench, and outer rise earthquakes on the subducting lower plate as it bends near the trench. Anomalously deep events are a characteristic of subduction zones, which produce the deepest quakes on the planet. Earthquakes are generally restricted to the shallow, brittle parts of the crust, generally at depths of less than twenty kilometers. However, in subduction zones quakes occur at depths as great as 700 km (430 mi). These quakes define inclined zones of seismicity known as Wadati–Benioff zones which trace

7134-609: The crust, through hotspot magmatism or extensional rifting, would the crust be able to break from its continent and begin subduction. Subduction can continue as long as the oceanic lithosphere moves into the subduction zone. However, the arrival of buoyant continental lithosphere at a subduction zone can result in increased coupling at the trench and cause plate boundary reorganization. The arrival of continental crust results in continental collision or terrane accretion that may disrupt subduction. Continental crust can subduct to depths of 250 km (160 mi) where it can reach

7257-523: The declaration of alert level 3 for the volcano, the United States issued an advisory cautioning its nationals from traveling to Mayon. Canada and the United Kingdom also posted advisories discouraging their nationals from visiting the volcano. The United States government committed $ 100,000 in financial aid for the evacuees of Mayon. In cooperation with the Philippine government the assistance

7380-448: The degree of lower plate curvature of the subducting plate in great historical earthquakes such as the 2004 Sumatra-Andaman and the 2011 Tōhoku earthquake, it was determined that the magnitude of earthquakes in subduction zones is inversely proportional to the angle of subduction near the trench, meaning that "the flatter the contact between the two plates, the more likely it is that mega-earthquakes will occur". Outer rise earthquakes on

7503-440: The descending slab. Nine of the ten largest earthquakes of the last 100 years were subduction zone megathrust earthquakes. These included the 1960 Great Chilean earthquake which at M 9.5 was the largest earthquake ever recorded, the 2004 Indian Ocean earthquake and tsunami , and the 2011 Tōhoku earthquake and tsunami . The subduction of cold oceanic lithosphere into the mantle depresses the local geothermal gradient and causes

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7626-455: The different regimes present in this setting. The models are as follows: In their 2019 study, Macdonald et al. proposed that arc-continent collision zones and the subsequent obduction of oceanic lithosphere was at least partially responsible for controlling global climate. Their model relies on arc-continent collision in tropical zones, where exposed ophiolites composed mainly of mafic material increase "global weatherability" and result in

7749-442: The diminishing volume of lava extruded from the summit. PHILVOLCS Alert Level 4 was lowered to Level 3 on September 11; to Level 2 on October 3; and to Level 1 on October 25. On August 10, a small summit explosion ejected ash 200 meters (660 ft) above the summit, which drifted east-northeast. In the weeks prior to the eruption, a visible glow increased within the crater and increased seismicity. On July 10, 2009, PHIVOLCS raised

7872-582: The evacuees back to their homes, while food supplies and temporary employment through the Department of Social Welfare and Development (DSWD) were provided to the heads of each family. As of January 3, 2010, the National Disaster Coordinating Council reported the overall cost of humanitarian aid and other assistance provided by the government and non-government organizations (NGOs) has reached over 61 million pesos since

7995-619: The forearc may include an accretionary wedge of sediments scraped off the subducting slab and accreted to the overriding plate. However, not all arc-trench complexes have an accretionary wedge. Accretionary arcs have a well-developed forearc basin behind the accretionary wedge, while the forearc basin is poorly developed in non-accretionary arcs. Beyond the forearc basin, volcanoes are found in long chains called volcanic arcs . The subducting basalt and sediment are normally rich in hydrous minerals and clays. Additionally, large quantities of water are introduced into cracks and fractures created as

8118-420: The forearc-hanging wall and not subducted. Most metamorphic phase transitions that occur within the subducting slab are prompted by the dehydration of hydrous mineral phases. The breakdown of hydrous mineral phases typically occurs at depths greater than 10 km. Each of these metamorphic facies is marked by the presence of a specific stable mineral assemblage, recording the metamorphic conditions undergone but

8241-414: The heavier plate dives beneath the other and sinks into the mantle. A region where this process occurs is known as a subduction zone , and its surface expression is known as an arc-trench complex . The process of subduction has created most of the Earth's continental crust. Rates of subduction are typically measured in centimeters per year, with rates of convergence as high as 11 cm/year. Subduction

8364-415: The highest, Alert Level 5, with at least eight towns and one city warned of possible explosions with ash and lava flows, and several thousands forced to evacuate even outside identified danger zones. The most violent eruptions were occurred from February 28 to March 1, and since then, declining activity was observed until April. The National Disaster Risk Reduction and Management Council (NDCC)reported that

8487-401: The hikers were soon located by the authorities. However, due to rugged and slippery terrain, the hikers' remains were slowly transferred from Camp 2 to Camp 1, the site of the rescue operations at the foot of the volcano. According to Butch Rivera of Bicol Regional Training and Teaching Hospital , the hikers died due to trauma in their bodies, and suffocation. Authorities were also able to rescue

8610-430: The idea of subduction initiation at passive margins is popular, there is no modern day example for this type of subduction nucleation. This is likely due to the strength of the oceanic or transitional crust at the continental passive margins, suggesting that if the crust did not break in its first 20 million years of life, it is unlikely to break in the future under normal sedimentation loads. Only with additional weaking of

8733-603: The language into different dialects is mainly because of the influence of other Bikol and non-Bikol languages surrounding the region. The Canaman dialect, despite being used only by a small portion of the population in Camarines Sur, is the standard form of Central Bikol used in literature, Catholic religious rites and mass media. Naga City dialect is spoken in the first, second, third districts (except in Del Gallego, where residents are mostly Tagalog speakers), and in

8856-574: The lower plate occur when normal faults oceanward of the subduction zone are activated by flexure of the plate as it bends into the subduction zone. The 2009 Samoa earthquake is an example of this type of event. Displacement of the sea floor caused by this event generated a six-meter tsunami in nearby Samoa. Seismic tomography has helped detect subducted lithospheric slabs deep in the mantle where no earthquakes occur. About one hundred slabs have been described in terms of depth and their timing and location of subduction. The great seismic discontinuities in

8979-484: The mantle, at 410 km (250 mi) depth and 670 km (420 mi), are disrupted by the descent of cold slabs in deep subduction zones. Some subducted slabs seem to have difficulty penetrating the major discontinuity that marks the boundary between the upper mantle and lower mantle at a depth of about 670 kilometers. Other subducted oceanic plates have sunk to the core–mantle boundary at 2890 km depth. Generally, slabs decelerate during their descent into

9102-463: The mantle, from typically several cm/yr (up to ~10 cm/yr in some cases) at the subduction zone and in the uppermost mantle, to ~1 cm/yr in the lower mantle. This leads to either folding or stacking of slabs at those depths, visible as thickened slabs in seismic tomography. Below ~1700 km, there might be a limited acceleration of slabs due to lower viscosity as a result of inferred mineral phase changes until they approach and finally stall at

9225-431: The next two consecutive years. On January 5, a 5-km-high ash column was produced by an explosion. Growth of summit-crater dome and intensifying eruptions later signaled evacuations. Past emissions had led to the growth of the lava dome beginning on February 12. On February 23, series of eruptions began. PHIVOLCS then recommended evacuation even beyond the permanent danger zone. On February 24, PHIVOLCS raised its status to

9348-492: The ocean floor, studied the Mid-Atlantic Ridge and proposed that hot molten rock was added to the crust at the ridge and expanded the seafloor outward. This theory was to become known as seafloor spreading . Since the Earth's circumference has not changed over geologic time, Hess concluded that older seafloor has to be consumed somewhere else, and suggested that this process takes place at oceanic trenches , where

9471-467: The outermost light crust plus the uppermost rigid portion of the mantle . Oceanic lithosphere ranges in thickness from just a few km for young lithosphere created at mid-ocean ridges to around 100 km (62 mi) for the oldest oceanic lithosphere. Continental lithosphere is up to 200 km (120 mi) thick. The lithosphere is relatively cold and rigid compared with the underlying asthenosphere , and so tectonic plates move as solid bodies atop

9594-399: The overriding continent. When the lower plate subducts at a shallow angle underneath a continent (something called "flat-slab subduction"), the subducting plate may have enough traction on the bottom of the continental plate to cause the upper plate to contract by folding, faulting, crustal thickening, and mountain building. Flat-slab subduction causes mountain building and volcanism moving into

9717-404: The planet. The ocean-ocean plate relationship can lead to subduction zones between oceanic and continental plates, therefore highlighting how important it is to understand this subduction setting. Although it is not fully understood what causes the initiation of subduction of an oceanic plate under another oceanic plate, there are three main models put forth by Baitsch-Ghirardello et al. that explain

9840-590: The possibility of spontaneous subduction from inherent density differences between two plates at specific locations like passive margins and along transform faults . There is evidence this has taken place in the Izu-Bonin-Mariana subduction system. Earlier in Earth's history, subduction is likely to have initiated without horizontal forcing due to the lack of relative plate motion, though a proposal by A. Yin suggests that meteorite impacts may have contributed to subduction initiation on early Earth. Though

9963-520: The pressures and temperatures necessary for this type of metamorphism are much higher than what is observed in most subduction zones. Frezzoti et al. (2011) propose a different mechanism for carbon transport into the overriding plate via dissolution (release of carbon from carbon-bearing minerals into an aqueous solution) instead of decarbonation. Their evidence comes from the close examination of mineral and fluid inclusions in low-temperature (<600 °C) diamonds and garnets found in an eclogite facies in

10086-444: The rocks of the mantle. The mantle-derived magmas (which are initially basaltic in composition) can ultimately reach the Earth's surface, resulting in volcanic eruptions. The chemical composition of the erupting lava depends upon the degree to which the mantle-derived basalt interacts with (melts) Earth's crust or undergoes fractional crystallization . Arc volcanoes tend to produce dangerous eruptions because they are rich in water (from

10209-436: The sedimentary and volcanic cover is mostly scraped off to form an orogenic wedge. An orogenic wedge is larger than most accretionary wedges due to the volume of material there is to accrete. The continental basement rocks beneath the weak cover suites are strong and mostly cold, and can be underlain by a >200 km thick layer of dense mantle. After shedding the low density cover units, the continental plate, especially if it

10332-450: The sinking oceanic plate they are attached to. Where continents are attached to oceanic plates with no subduction, there is a deep basin that accumulates thick suites of sedimentary and volcanic rocks known as a passive margin. Some passive margins have up to 10 km of sedimentary and volcanic rocks covering the continental crust. As a passive margin is pulled into a subduction zone by the attached and negatively buoyant oceanic lithosphere,

10455-453: The slab and sediments) and tend to be extremely explosive. Krakatoa , Nevado del Ruiz , and Mount Vesuvius are all examples of arc volcanoes. Arcs are also associated with most ore deposits. Beyond the volcanic arc is a back-arc region whose character depends strongly on the angle of subduction of the subducting slab. Where this angle is shallow, the subducting slab drags the overlying continental crust partially with it, which produces

10578-580: The southeastern rim of the crater and heightened seismic activity caused PHIVOLCS to increase the alert level for Mayon from 2 to 3, which indicates relatively high unrest with magma at the crater, and that hazardous eruption is possible within weeks. The rockfalls and visible incandescence of the crater from molten lava and hot volcanic gas both indicated a possible incipient breaching of the growing summit lava dome. On September 15, NASA's Moderate-Resolution Imaging Spectroradiometer (MODIS) detected thermal anomalies near Mayon's summit, consistent with magma at

10701-606: The southern and southwestern lower slopes. Composed of olivine -augite basalt, these cones have an angle of repose of 34%, with Ligñon Hill as an example. Like other volcanoes around the Pacific Ocean , Mayon is a part of the Pacific Ring of Fire . It is on the southeast side of Luzon . The Bicol Arc is one of 7 oceanic trench subduction zones defining the Philippine Mobile Belt . Volcanism in

10824-406: The southern portion of the volcano and an increase in sulfur dioxide emission to 750 tonnes per day. Almost 460 earthquakes in the volcano were monitored. In the border of the danger zone, rumbling sounds like thunder were heard. Over 9,000 families (44,394 people) were evacuated by the Philippine government from the base of the volcano. No civilian was permitted within the 8 km danger zone, which

10947-472: The start of the activity: At the date of my visit, the volcano had poured out, for five months continuously, a stream of lava on the Legaspi side from the very summit. The viscid mass bubbled quietly but grandly, and overran the border of the crater, descending several hundred feet in a glowing wave, like red-hot iron. Gradually, fading as the upper surface cooled, it changed to a thousand sparkling rills among

11070-600: The start of the eruption. The United Nations World Food Programme (UN-WFP) delivered 20 tons of high energy biscuits to the evacuees to complement supplies provided by the DSWD, with more allocated from emergency food stocks intended for relief from the effects of the 2009 Pacific typhoon season. When the alert level was downgraded to level 3 on January 2, 2010, UN-WFP provided three days worth of food for evacuees returning to their homes who will continue to receive supplies already set aside for them. On May 7, at 8 a.m. ( PST ),

11193-401: The status from Alert Level 1 (low level unrest) to Alert Level 2 (moderate unrest) because the number of recorded low frequency volcanic earthquakes rose to the same level as those prior to the 2008 phreatic explosion . At 5:32 a.m. on October 28, a minor ash explosion lasting for about one minute occurred in the summit crater. A brown ash column rose about 600 meters (2,000 ft) above

11316-514: The status of the volcano, "You might think it is taking a break but the volcano is still swelling." On the next day December 29, a civil aviation warning for the airspace near the summit was included in the volcano bulletins. The ejected volcanic material since the start of the eruption was estimated to have been between 20 million to 23 million cubic meters of rocks and volcanic debris, compared to 50 million to 60 million cubic meters in past eruptions. On January 2, 2010, PHIVOLCS lowered

11439-447: The storage of carbon through silicate weathering processes. This storage represents a carbon sink , removing carbon from the atmosphere and resulting in global cooling. Their study correlates several Phanerozoic ophiolite complexes, including active arc-continent subduction, with known global cooling and glaciation periods. This study does not discuss Milankovitch cycles as a driver of global climate cyclicity. Modern-style subduction

11562-481: The stratosphere during violent eruptions can cause rapid cooling of Earth's climate and affect air travel. Arc-magmatism plays a role in Earth's Carbon cycle by releasing subducted carbon through volcanic processes. Older theory states that the carbon from the subducting plate is made available in overlying magmatic systems via decarbonation, where CO 2 is released through silicate-carbonate metamorphism. However, evidence from thermodynamic modeling has shown that

11685-399: The subducted plate and in the overlying mantle wedge. This type of melting selectively concentrates volatiles and transports them into the overlying plate. If an eruption occurs, the cycle then returns the volatiles into the oceans and atmosphere. The surface expressions of subduction zones are arc-trench complexes. On the ocean side of the complex, where the subducting plate first approaches

11808-434: The subducting plate trigger volcanism in the overriding plate. If the subducting plate sinks at a shallow angle, the overriding plate develops a belt of deformation characterized by crustal thickening, mountain building , and metamorphism . Subduction at a steeper angle is characterized by the formation of back-arc basins . According to the theory of plate tectonics , the Earth's lithosphere , its rigid outer shell,

11931-526: The subducting slab bends downward. During the transition from basalt to eclogite, these hydrous materials break down, producing copious quantities of water, which at such great pressure and temperature exists as a supercritical fluid . The supercritical water, which is hot and more buoyant than the surrounding rock, rises into the overlying mantle, where it lowers the melting temperature of the mantle rock, generating magma via flux melting . The magmas, in turn, rise as diapirs because they are less dense than

12054-509: The subducting slab. Transitions between facies cause hydrous minerals to dehydrate at certain pressure-temperature conditions and can therefore be tracked to melting events in the mantle beneath a volcanic arc. Two kinds of arcs are generally observed on Earth: island arcs that form on the oceanic lithosphere (for example, the Mariana and the Tonga island arcs), and continental arcs such as

12177-446: The subduction zone, there is often an outer trench high or outer trench swell . Here the plate shallows slightly before plunging downwards, as a consequence of the rigidity of the plate. The point where the slab begins to plunge downwards is marked by an oceanic trench . Oceanic trenches are the deepest parts of the ocean floor. Beyond the trench is the forearc portion of the overriding plate. Depending on sedimentation rates,

12300-451: The subject, performs the action of overriding the object, the lower plate, which is overridden. Subduction zones are important for several reasons: Subduction zones have also been considered as possible disposal sites for nuclear waste in which the action of subduction itself would carry the material into the planetary mantle , safely away from any possible influence on humanity or the surface environment. However, that method of disposal

12423-445: The summit, and incandescent fragments from the lava pile continuously rolling down Bonga Gully reached a distance of 3–4 km below the summit. By midday, a total of 33,833 people from 7,103 families had been evacuated, 72 percent of the total number of people that needed to be evacuated, according to Albay Governor Joey Salceda. On December 20, PHIVOLCS raised Mayon's status level to alert level 4 because of an increasing lava flow in

12546-420: The summit. Sulfur dioxide (SO 2 ) emission was measured at a 757 tonnes after a peak of 2,360 tonnes on September 6. Deformation (precise leveling and tiltmeters ) during the 3rd week of August 2014 recorded edifice inflation. On January 13, at 4:21 pm (PST), a phreatic eruption occurred that propelled a grayish steam and ash plume approximately 2500 meters high that drifted to the southwest side of

12669-471: The summit. By evening, Albay Province authorities evacuated about 20,000 residents out of the 8-kilometre (5.0 mi) danger zone and into local evacuation centres. About 50,000 people live within the 8-kilometre (5.0 mi) zone. On December 17, five ash ejections occurred, with one reaching 500 meters (1,600 ft) above the summit. Sulfur dioxide emission increased to 2,758 tonnes per 24 hours, lava flows reached down to 1,500 metres (4,900 ft) below

12792-454: The surface once the volcanoes have weathered away. The volcanism and plutonism occur as a consequence of the subducting oceanic slab dehydrating as it reaches higher pressures and temperatures. Once the oceanic slab reaches about 100 km in depth, hydrous minerals become unstable and release fluids into the asthenosphere. The fluids act as a flux for the rock within the asthenosphere and cause it to partially melt. The partially melted material

12915-406: The surface. On September 16, provincial governor Joey Salceda said that the government would begin to "fast-track the preparation to evacuate 12,000 families in the 6–8 km extended danger zone", and soldiers would enforce the no-go areas. On September 18, PHIVOLCS reported 142 VT earthquake events and 251 rockfall events. White steam plumes drifted to the south-southwest and rain clouds covered

13038-439: The timing and conditions in which these dehydration reactions occur is key to interpreting mantle melting, volcanic arc magmatism, and the formation of continental crust. A metamorphic facies is characterized by a stable mineral assemblage specific to a pressure-temperature range and specific starting material. Subduction zone metamorphism is characterized by a low temperature, high-ultrahigh pressure metamorphic path through

13161-456: The town of Cagsawa with tephra that buried it. Trees burned, and rivers were certainly damaged. Proximate areas were also devastated by the eruption, with ash accumulating to 9 m (30 ft) in depth. In Cagsawa town, about 1,200 locals perished in what is considered to be the most lethal eruption in Mayon's history according to PHIVOLCS. The 1814 eruption is believed to have contributed to

13284-444: The trench and approximately one hundred kilometers above the subducting slab. Arcs produce about 10% of the total volume of magma produced each year on Earth (approximately 0.75 cubic kilometers), much less than the volume produced at mid-ocean ridges, but they have formed most continental crust . Arc volcanism has the greatest impact on humans because many arc volcanoes lie above sea level and erupt violently. Aerosols injected into

13407-495: The use of emergency measures and gave the authorities clearance to forcibly evacuate residents who refused to leave. When the alert level around the volcano was lowered from alert level 4 to alert level 3 on January 2, 2010, the Albay provincial government ordered a decampment of some 47,000 displaced residents from the evacuation centers. Power and water supply in the danger zones were restored. Military vehicles were used to transport

13530-410: The vent; the status was later raised to Alert Level 2. The emission was recorded by the seismic network of the Philippine Institute of Volcanology and Seismology as an explosion that lasted for 10 minutes. No volcanic earthquakes nor other visible signs of abnormal activity were observed before the explosion. Mayon had experienced continuous emissions since 1999 and followed by a series of eruptions in

13653-413: The village of Bacacay was buried 15 m (49 ft) beneath the lava. In Santo Domingo 100 people were killed by steam and falling debris or hot rocks. Other villages like San Roque, Santa Misericordia and Santo Niño became deathtraps. Ash was carried in black clouds as far as 160 kilometers (99 mi) from the catastrophic event, which killed more than 400 people. No casualties were recorded from

13776-457: The volcano produced a surprise phreatic eruption lasting 73 seconds. Ash , steam and rock were produced during this eruption. Ash clouds reached 500 meters above the volcano's summit and drifted west southwest. The event killed five climbers, of whom three were German , one was a Spaniard living in Germany, and one was a Filipino tour guide. Seven others were reported injured. The bodies of

13899-530: The volcano. In the 24-hour period, the seismic network recorded 20 volcanic earthquakes. Alert Status was kept at Level 2. At 8 pm on December 14, after 83 volcanic quakes in the preceding 24 hours and increased sulfur dioxide emissions, PHIVOLCS raised the Alert status to Level 3. Early in the morning of December 15, a moderate ash explosion occurred at the summit crater and "quiet extrusion of lava" resulted in flows down to about 500 meters (1,600 ft) from

14022-635: The volcano. The activity lasted approximately 1 hour and 47 minutes and ash fell in Barangay Anoling, Daraga, Barangays Sua, Quirangay, Tumpa, Ilawod and Salugan of Camalig and in Barangays Tandarora, Maninila, and Travesia in Guinobatan. Sulfuric odor was noted by residents of Camalig town proper. Rumbling sounds were also heard by residents of Brgy. Anoling, Daraga and rockfall events were intermittently recorded. Faint crater glow

14145-505: The western and eastern portions of the fourth district (Caramoan, Garchitorena, Presentacion, Siruma and Tinambac) of Camarines Sur. It is also spoken in San Pascual, Masbate (Burias Island) and the southwestern part of Catanduanes. The Partido dialect is spoken in the eastern part of Camarines Sur centered in the southern portion of the fourth districts (Goa, Lagonoy, Sagñay, San Jose, and Tigaon). The Tabaco-Legazpi-Sorsogon (TLS) dialect

14268-574: Was being planned. The government of the United Kingdom advised its nationals to follow the advisories given by the local authorities, and respect the 6 km permanent danger zone. The advisory was given a day after the explosion. On August 12, a new 30–50 meter high lava dome appeared in the summit crater. This event was preceded by inflations of the volcano (measured by precise leveling, tilt data, and GPS ), and increases in sulfur dioxide gas emissions. On September 14, rockfall events at

14391-628: Was caused by subduction of the Indo-Australian plate under the Euro-Asian Plate, but the tsunami spread over most of the planet and devastated the areas around the Indian Ocean. Small tremors which cause small, nondamaging tsunamis, also occur frequently. A study published in 2016 suggested a new parameter to determine a subduction zone's ability to generate mega-earthquakes. By examining subduction zone geometry and comparing

14514-516: Was cordoned off by the Philippine military who actively patrolled to enforce the "no-go" rule and to ensure no damage or loss of property of those evacuated. Alert level 4 was maintained as the volcano remained restive through December, prompting affected residents to spend Christmas and the New Year in evacuation centers. On December 25, sulfur dioxide emissions peaked at 8,993 tons per day. On December 28, PHIVOLCS director Renato Solidum commented on

14637-567: Was declared a national park on July 20, 1938, the first in the nation. It was reclassified as a natural park and renamed the Mayon Volcano Natural Park in 2000. It is the centerpiece of the Albay Biosphere Reserve, declared by UNESCO in 2016, and is currently being nominated as a World Heritage Site . Mayon is the most active volcano in the Philippines, and its activity is regularly monitored by

14760-507: Was delivered through the Philippine National Red Cross and other NGOs by USAID . The Albay provincial government ordered the local military to add more checkpoints, place roadblocks and arrest tourists caught traveling inside the 8-kilometer (5.0 mi) danger zone. Power and water supply were cut off within the danger zone to further discourage residents from returning. The Commission on Human Rights allowed

14883-475: Was first observed at 10:16 pm. The event prompted PHIVOLCS to raise the Alert Level of Mayon from Alert Level 1 (abnormal) to Alert Level 2- (increasing unrest for the people's safety). About 40,000 residents were displaced in the resulting evacuation. On January 14, Mayon's alert status was upgraded to Alert Level 3 (increased tendency towards a hazardous eruption) after 3 phreatic eruptions and 158 rockfall events were recorded. The summit crater also exhibited

15006-582: Was once hotter, but not that subduction conditions were hotter. Previously, the lack of pre-Neoproterozoic blueschist was thought to indicate a different type of subduction. Both lines of evidence refute previous conceptions of modern-style subduction having been initiated in the Neoproterozoic Era 1.0 Ga ago. Harry Hammond Hess , who during World War II served in the United States Navy Reserve and became fascinated in

15129-489: Was reported that some tourists lured by local "guides" ignored government warnings not to venture into the 8-kilometre (5.0 mi) danger zone. "It's a big problem. I think the first violation of the zero casualty (record) will be a dead tourist," said Salceda. Speaking about thrill-seekers finding their way into the area, Salceda warned, "At the moment of the eruption, the local guides will have better chance of getting out. The helpless tourist will be left behind." Following

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