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69-595: Methana is situated on a volcanic (the Methana Volcano ) peninsula , attached to the Peloponnese. Administratively, it belongs to the Attica region. The town (pop. 892 in 2011) is located north of the road connecting to the rest of the Peloponnese and Galatas. The highest point is 740 metres (2,428 feet) (Helona Mountain). The municipal unit has a land area of 50.161 square kilometres (19.367 square miles) and

138-542: A ghost town ) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE. Pausanias (geographer) Pausanias ( / p ɔː ˈ s eɪ n i ə s / paw- SAY -nee-əs ; ‹See Tfd› Greek : Παυσανίας ; c.  110  – c.  180 ) was a Greek traveler and geographer of the second century AD. He is famous for his Description of Greece ( Ἑλλάδος Περιήγησις , Hēlládos Periḗgēsis ),

207-484: A magma chamber below the surface. The process that forms volcanoes is called volcanism . On Earth, volcanoes are most often found where tectonic plates are diverging or converging , and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas

276-437: A graduated spectrum, with much overlap between categories, and does not always fit neatly into only one of these three separate categories. The USGS defines a volcano as "erupting" whenever the ejection of magma from any point on the volcano is visible, including visible magma still contained within the walls of the summit crater. While there is no international consensus among volcanologists on how to define an active volcano,

345-568: A lasting written account of "all things Greek", or panta ta hellenika . Being born in Asia Minor , Pausanias was of Greek heritage. He grew up and lived under the rule of the Roman Empire , but valued his Greek identity, history, and culture. He was keen to describe the glories of a Greek past that still was relevant in his lifetime, even if the country was beholden to Rome as a dominating imperial force. Pausanias's pilgrimage throughout

414-485: A lengthy work that describes ancient Greece from his firsthand observations. Description of Greece provides crucial information for making links between classical literature and modern archaeology , which is providing evidence of the sites and cultural details he mentions although knowledge of their existence may have become lost or relegated to myth or legend. Nothing is known about Pausanias apart from what historians can piece together from his own writing. However, it

483-443: A paper was published suggesting a new definition for the word 'volcano' that includes processes such as cryovolcanism . It suggested that a volcano be defined as 'an opening on a planet or moon's surface from which magma , as defined for that body, and/or magmatic gas is erupted.' This article mainly covers volcanoes on Earth. See § Volcanoes on other celestial bodies and cryovolcano for more information. The word volcano

552-496: A past tense verb rather than the present tense in some instances. Their interpretation is that he did this in order to make it seem as if he were in the same temporal setting as his audience. Unlike a modern day travel guide, in Description of Greece Pausanias tends to elaborate with discussion of an ancient ritual or to impart a myth related to the site he is visiting. His style of writing would not become popular again until

621-534: A population of 1,352 inhabitants at the 2021 census. The municipal unit Methana is subdivided into the following communities (constituent villages in brackets): Half of the entire peninsula's population lives in Methana town. The peninsula is entirely of volcanic origin and contains over 30 volcanic eruption centers. The last volcanic eruption occurred near present-day Kameni Chora in 3rd century BC. Famous writers such as Ovid , Strabo and Pausanias reported

690-400: A smaller one and the mountains of the eastern tip of the neighboring peninsula. Much of the peninsula is mountainous and bushy and grassy. The mountain range covers the central part of the peninsula and has a small ridge north of the seat. The residential area is within the sea. The pastures are around Methana. A mountain ridge is founded in the west and is about 3 km (2 mi) long with

759-572: A stream in the middle and a cliff in the south. The earliest known settlement (near the village of Vathy) dates from 1500–1300 BC. The first survey was conducted by Michael Deffner , who discovered a large throne , among other artefacts. Many ancient sites were identified through the archaeological survey conducted in the 1980s by the University of Liverpool in association with the British School at Athens. The Acropolis Palaiokastro

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828-581: A topographical map of the entire peninsula at a scale of 1:25,000 was made. An interactive 3D map was created and is on the World Wide Web. Also a rich photographic archive with about 10.000 color slides has been produced (see links below). The panorama of the northeastern part of Argolis , southeastern and eastern Corinthia along with the southern part of the Attica peninsula and the Saronic Islands of Aegina and Salamis along with

897-632: A volcano is largely determined by the composition of the lava it erupts. The viscosity (how fluid the lava is) and the amount of dissolved gas are the most important characteristics of magma, and both are largely determined by the amount of silica in the magma. Magma rich in silica is much more viscous than silica-poor magma, and silica-rich magma also tends to contain more dissolved gases. Lava can be broadly classified into four different compositions: Mafic lava flows show two varieties of surface texture: ʻAʻa (pronounced [ˈʔaʔa] ) and pāhoehoe ( [paːˈho.eˈho.e] ), both Hawaiian words. ʻAʻa

966-555: A volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit; however, this describes just one of the many types of volcano. The features of volcanoes are varied. The structure and behaviour of volcanoes depend on several factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have landscape features such as massive plateaus . Vents that issue volcanic material (including lava and ash ) and gases (mainly steam and magmatic gases) can develop anywhere on

1035-465: A volcano that has experienced one or more eruptions that produced over 1,000 cubic kilometres (240 cu mi) of volcanic deposits in a single explosive event. Such eruptions occur when a very large magma chamber full of gas-rich, silicic magma is emptied in a catastrophic caldera -forming eruption. Ash flow tuffs emplaced by such eruptions are the only volcanic product with volumes rivalling those of flood basalts . Supervolcano eruptions, while

1104-739: Is a volcanic field of over 60 cinder cones. Based on satellite images, it has been suggested that cinder cones might occur on other terrestrial bodies in the Solar system too; on the surface of Mars and the Moon. Stratovolcanoes (composite volcanoes) are tall conical mountains composed of lava flows and tephra in alternate layers, the strata that gives rise to the name. They are also known as composite volcanoes because they are created from multiple structures during different kinds of eruptions. Classic examples include Mount Fuji in Japan, Mayon Volcano in

1173-412: Is characterized by a rough, clinkery surface and is the typical texture of cooler basalt lava flows. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Pāhoehoe flows are sometimes observed to transition to ʻaʻa flows as they move away from the vent, but never the reverse. More silicic lava flows take the form of block lava, where

1242-565: Is derived from the name of Vulcano , a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan , the god of fire in Roman mythology . The study of volcanoes is called volcanology , sometimes spelled vulcanology . According to the theory of plate tectonics, Earth's lithosphere , its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to convection in

1311-584: Is expressed using the volcanic explosivity index (VEI), which ranges from 0 for Hawaiian-type eruptions to 8 for supervolcanic eruptions. As of December 2022 , the Smithsonian Institution 's Global Volcanism Program database of volcanic eruptions in the Holocene Epoch (the last 11,700 years) lists 9,901 confirmed eruptions from 859 volcanoes. The database also lists 1,113 uncertain eruptions and 168 discredited eruptions for

1380-459: Is honest about his sourcing, sometimes confirming contemporary knowledge by him that may be lost to modern researchers. Until twentieth-century archaeologists concluded that Pausanias was a reliable guide to sites being excavated, classicists largely had dismissed the writings of Pausanias as purely literary. Following their presumed authoritative contemporary Ulrich von Wilamowitz-Moellendorff , classicists tended to regard him as little more than

1449-725: Is located near the village of Vathy but the main port is at Methana, also called Arsinoe in Ptolemaic times, with a fort on the islet of Nisaki. A coastal fortress called Akropolis Oga is located near Kypseli . A Mycenaean settlement was excavated by Helene Konstolakis-Jiannopoulou in 1990 along with the chapel of Agios Konstantinos and Elenis. Selected artifacts can be visited in the museums of Poros island and in Piraeus. This site dates between 1500 and 1300 BC. Methana ( ‹See Tfd› Greek : τὰ Μέθανα , tà Méthana ), Methone ( Μεθώνη , Methṓnē ), or Methene ( Μεθήνη , Methḗnē )

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1518-537: Is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analysed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near

1587-462: Is probable that he was born c.  110 AD into a Greek family and was probably a native of Lydia in Asia Minor. From c.  150 until his death around 180, Pausanias travelled throughout the mainland of Greece, writing about various monuments, sacred spaces, and significant geographical sites along the way. In writing his Description of Greece , Pausanias sought to put together

1656-471: Is typically low in silica, shield volcanoes are more common in oceanic than continental settings. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland , as well. Lava domes are built by slow eruptions of highly viscous lava. They are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount St. Helens , but can also form independently, as in

1725-617: The Cascade Volcanoes or the Japanese Archipelago , or the eastern islands of Indonesia . Hotspots are volcanic areas thought to be formed by mantle plumes , which are hypothesized to be columns of hot material rising from the core-mantle boundary. As with mid-ocean ridges, the rising mantle rock experiences decompression melting which generates large volumes of magma. Because tectonic plates move across mantle plumes, each volcano becomes inactive as it drifts off

1794-460: The Greek War of Independence , hundreds of refugees, mainly women and children, found refuge in the sparsely populated peninsula of Methana, so that the population of Methana rose from 500-600 in the pre-revolution years to 1,349 in 1830. In 1826-27 Charles Fabvier built a fortress on the isthmus of Methana, probably to protect his troops. In 1834 Methana became a municipality which was annexed to

1863-626: The Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere . Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines. Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus. Mars has significant volcanoes. In 2009,

1932-834: The landform and may give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Kīlauea in Hawaii. Volcanic craters are not always at the top of a mountain or hill and may be filled with lakes such as with Lake Taupō in New Zealand. Some volcanoes can be low-relief landform features, with the potential to be hard to recognize as such and be obscured by geological processes. Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter , Saturn , and Neptune ; and mud volcanoes , which are structures often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes except when

2001-535: The 2nd century, he saw a temple of Isis , and statutes of Hermes and Heracles in the agora . There are no written references to Methana in the Byzantine and Ottoman periods. Ruins of basilicas and churches from the late 6th or early 7th century have been found. It seems that there were two settlements in Methana in the Byzantine period, one at Panagitsa and another at Prophet Elias and at Helona. Another settlement seems to have existed west of Kounoupitsa , where

2070-883: The Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift , the Wells Gray-Clearwater volcanic field , and the Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary , 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism , of which

2139-622: The Philippines, and Mount Vesuvius and Stromboli in Italy. Ash produced by the explosive eruption of stratovolcanoes has historically posed the greatest volcanic hazard to civilizations. The lavas of stratovolcanoes are higher in silica, and therefore much more viscous, than lavas from shield volcanoes. High-silica lavas also tend to contain more dissolved gas. The combination is deadly, promoting explosive eruptions that produce great quantities of ash, as well as pyroclastic surges like

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2208-613: The USGS defines a volcano as active whenever subterranean indicators, such as earthquake swarms , ground inflation, or unusually high levels of carbon dioxide or sulfur dioxide are present. The USGS defines a dormant volcano as any volcano that is not showing any signs of unrest such as earthquake swarms, ground swelling, or excessive noxious gas emissions, but which shows signs that it could yet become active again. Many dormant volcanoes have not erupted for thousands of years, but have still shown signs that they may be likely to erupt again in

2277-510: The boundary with the Yukon Territory . Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although several processes may cause such activity. The largest structures are 10 kilometres in diameter and reach 700 meters high. The material that is expelled in a volcanic eruption can be classified into three types: The concentrations of different volcanic gases can vary considerably from one volcano to

2346-402: The case of Lassen Peak . Like stratovolcanoes, they can produce violent, explosive eruptions, but the lava generally does not flow far from the originating vent. Cryptodomes are formed when viscous lava is forced upward causing the surface to bulge. The 1980 eruption of Mount St. Helens was an example; lava beneath the surface of the mountain created an upward bulge, which later collapsed down

2415-479: The church of Agia Barbara is located and the churches of Agios Dimitrios and Agios Ioannis the Theologian, built in the 13th century and frescoed, are located. It seems that the peninsula was not affected by Slavic invasions, but later in medieval times it was affected by raids. During the 14th century, a period in which the population of the region was diluted, Arvanites settled on the Methana peninsula. During

2484-444: The early nineteenth century when contemporary travel guides resembled his. In the topographical aspect of his work, Pausanias makes many natural history digressions on the wonders of nature documented at the time, the signs that herald the approach of an earthquake , the phenomena of the tides , the ice-bound seas of the north, and that at the summer solstice the noonday sun casts no shadow at Syene ( Aswan ). While he never doubts

2553-799: The enormous area they cover, and subsequent concealment under vegetation and glacial deposits, supervolcanoes can be difficult to identify in the geologic record without careful geologic mapping . Known examples include Yellowstone Caldera in Yellowstone National Park and Valles Caldera in New Mexico (both western United States); Lake Taupō in New Zealand; Lake Toba in Sumatra , Indonesia; and Ngorongoro Crater in Tanzania. Volcanoes that, though large, are not large enough to be called supervolcanoes, may also form calderas in

2622-439: The existence of the deities and heroes, he criticizes some of the myths and legends he encountered during his travels as differing from earlier cultural traditions that he relates or notes. His descriptions of monuments of art are plain and unadorned, bearing a solid impression of reality. Pausanias is frank in acknowledging personal limitations. When he quotes information at second hand rather than relating his own experiences, he

2691-431: The flow is covered with angular, vesicle-poor blocks. Rhyolitic flows typically consist largely of obsidian . Tephra is made when magma inside the volcano is blown apart by the rapid expansion of hot volcanic gases. Magma commonly explodes as the gas dissolved in it comes out of solution as the pressure decreases when it flows to the surface . These violent explosions produce particles of material that can then fly from

2760-610: The formation of a submarine volcano off the coast of Mayotte . Subglacial volcanoes develop underneath ice caps . They are made up of lava plateaus capping extensive pillow lavas and palagonite . These volcanoes are also called table mountains, tuyas , or (in Iceland) mobergs. Very good examples of this type of volcano can be seen in Iceland and in British Columbia . The origin of the term comes from Tuya Butte , which

2829-585: The future. In an article justifying the re-classification of Alaska's Mount Edgecumbe volcano from "dormant" to "active", volcanologists at the Alaska Volcano Observatory pointed out that the term "dormant" in reference to volcanoes has been deprecated over the past few decades and that "[t]he term "dormant volcano" is so little used and undefined in modern volcanology that the Encyclopedia of Volcanoes (2000) does not contain it in

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2898-466: The glossaries or index", however the USGS still widely employs the term. Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalization is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the Chaitén volcano in 2008. Modern volcanic activity monitoring techniques, and improvements in

2967-492: The interior of a continent and lead to rifting. Early stages of rifting are characterized by flood basalts and may progress to the point where a tectonic plate is completely split. A divergent plate boundary then develops between the two halves of the split plate. However, rifting often fails to completely split the continental lithosphere (such as in an aulacogen ), and failed rifts are characterized by volcanoes that erupt unusual alkali lava or carbonatites . Examples include

3036-565: The land of his ancestors was his own attempt to establish a place in the world for this new Roman Greece, connecting myths and stories of ancient culture to those of his own time. Pausanias has a straightforward and simple writing style. He is, overall, direct in his language, writing his stories and descriptions unelaborately. However, some translators have noted that Pausanias's use of various prepositions and tenses may be confusing and difficult to render in English. For example, Pausanias may use

3105-522: The last volcanic eruption in Methana. The peninsula is the northwesternmost of the arc of the Aegean islands of which the active volcanic areas are Methana, Milos , Santorini and Nisyros . In the future, Methana (and the area of the Saronic gulf ) may expect other volcanic eruptions. Since 1991, the peninsula has been investigated by the team of ETH Zürich geologically and cartographically. From this,

3174-419: The mid-oceanic ridge is above sea level, volcanic islands are formed, such as Iceland . Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. The oceanic plate subducts (dives beneath the continental plate), forming a deep ocean trench just offshore. In a process called flux melting , water released from the subducting plate lowers the melting temperature of

3243-551: The modelling of the factors that produce eruptions, have helped the understanding of why volcanoes may remain dormant for a long time, and then become unexpectedly active again. The potential for eruptions, and their style, depend mainly upon the state of the magma storage system under the volcano, the eruption trigger mechanism and its timescale. For example, the Yellowstone volcano has a repose/recharge period of around 700,000 years, and Toba of around 380,000 years. Vesuvius

3312-415: The most dangerous type, are very rare; four are known from the last million years , and about 60 historical VEI 8 eruptions have been identified in the geologic record over millions of years. A supervolcano can produce devastation on a continental scale, and severely cool global temperatures for many years after the eruption due to the huge volumes of sulfur and ash released into the atmosphere. Because of

3381-438: The mud volcano is actually a vent of an igneous volcano. Volcanic fissure vents are flat, linear fractures through which lava emerges. Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically but are characterized by relatively gentle effusive eruptions . Since low-viscosity magma

3450-452: The next. Water vapour is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide . Other principal volcanic gases include hydrogen sulfide , hydrogen chloride , and hydrogen fluoride . A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen , carbon monoxide , halocarbons , organic compounds, and volatile metal chlorides. The form and style of an eruption of

3519-876: The north side of the mountain. Cinder cones result from eruptions of mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 metres (100 to 1,300 ft) high. Most cinder cones erupt only once and some may be found in monogenetic volcanic fields that may include other features that form when magma comes into contact with water such as maar explosion craters and tuff rings . Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. In New Mexico , Caja del Rio

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3588-549: The ocean surface as new islands or floating pumice rafts . In May and June 2018, a multitude of seismic signals were detected by earthquake monitoring agencies all over the world. They took the form of unusual humming sounds, and some of the signals detected in November of that year had a duration of up to 20 minutes. An oceanographic research campaign in May 2019 showed that the previously mysterious humming noises were caused by

3657-420: The ocean surface, due to the rapid cooling effect and increased buoyancy in water (as compared to air), which often causes volcanic vents to form steep pillars on the ocean floor. Hydrothermal vents are common near these volcanoes, and some support peculiar ecosystems based on chemotrophs feeding on dissolved minerals. Over time, the formations created by submarine volcanoes may become so large that they break

3726-471: The ocean's surface. In the deep ocean basins, the tremendous weight of the water prevents the explosive release of steam and gases; however, submarine eruptions can be detected by hydrophones and by the discoloration of water because of volcanic gases . Pillow lava is a common eruptive product of submarine volcanoes and is characterized by thick sequences of discontinuous pillow-shaped masses which form underwater. Even large submarine eruptions may not disturb

3795-468: The one that destroyed the city of Saint-Pierre in Martinique in 1902. They are also steeper than shield volcanoes, with slopes of 30–35° compared to slopes of generally 5–10°, and their loose tephra are material for dangerous lahars . Large pieces of tephra are called volcanic bombs . Big bombs can measure more than 1.2 metres (4 ft) across and weigh several tons. A supervolcano is defined as

3864-425: The overlying mantle wedge, thus creating magma . This magma tends to be extremely viscous because of its high silica content, so it often does not reach the surface but cools and solidifies at depth . When it does reach the surface, however, a volcano is formed. Thus subduction zones are bordered by chains of volcanoes called volcanic arcs . Typical examples are the volcanoes in the Pacific Ring of Fire , such as

3933-619: The plume, and new volcanoes are created where the plate advances over the plume. The Hawaiian Islands are thought to have been formed in such a manner, as has the Snake River Plain , with the Yellowstone Caldera being part of the North American plate currently above the Yellowstone hotspot . However, the mantle plume hypothesis has been questioned. Sustained upwelling of hot mantle rock can develop under

4002-508: The province of Kalavria, consisting of the municipalities of Methana, Troizina, Dryopi and Kalavria. [REDACTED]  This article incorporates text from a publication now in the public domain :  Smith, William , ed. (1854–1857). "Methana". Dictionary of Greek and Roman Geography . London: John Murray. Volcano A volcano is a rupture in the crust of a planetary-mass object , such as Earth , that allows hot lava , volcanic ash , and gases to escape from

4071-435: The same time interval. Volcanoes vary greatly in their level of activity, with individual volcanic systems having an eruption recurrence ranging from several times a year to once in tens of thousands of years. Volcanoes are informally described as erupting , active , dormant , or extinct , but the definitions of these terms are not entirely uniform among volcanologists. The level of activity of most volcanoes falls upon

4140-492: The same way; they are often described as "caldera volcanoes". Submarine volcanoes are common features of the ocean floor. Volcanic activity during the Holocene Epoch has been documented at only 119 submarine volcanoes, but there may be more than one million geologically young submarine volcanoes on the ocean floor. In shallow water, active volcanoes disclose their presence by blasting steam and rocky debris high above

4209-622: The solidified erupted material that makes up the mantle of a volcano may be stripped away that its inner anatomy becomes apparent. Using the metaphor of biological anatomy , such a process is called "dissection". Cinder Hill , a feature of Mount Bird on Ross Island , Antarctica , is a prominent example of a dissected volcano. Volcanoes that were, on a geological timescale, recently active, such as for example Mount Kaimon in southern Kyūshū , Japan , tend to be undissected. Eruption styles are broadly divided into magmatic, phreatomagmatic, and phreatic eruptions. The intensity of explosive volcanism

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4278-406: The surrounding areas, and initially not seismically monitored before its unanticipated and catastrophic eruption of 1991. Two other examples of volcanoes that were once thought to be extinct, before springing back into eruptive activity were the long-dormant Soufrière Hills volcano on the island of Montserrat , thought to be extinct until activity resumed in 1995 (turning its capital Plymouth into

4347-434: The theory of plate tectonics. For example, some volcanoes are polygenetic with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are monogenetic (meaning "one life") and such volcanoes are often grouped together in a geographical region. At the mid-ocean ridges , two tectonic plates diverge from one another as hot mantle rock creeps upwards beneath

4416-444: The thinned oceanic crust . The decrease of pressure in the rising mantle rock leads to adiabatic expansion and the partial melting of the rock, causing volcanism and creating new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans, and so most volcanic activity on Earth is submarine, forming new seafloor . Black smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where

4485-431: The underlying ductile mantle , and most volcanic activity on Earth takes place along plate boundaries, where plates are converging (and lithosphere is being destroyed) or are diverging (and new lithosphere is being created). During the development of geological theory, certain concepts that allowed the grouping of volcanoes in time, place, structure and composition have developed that ultimately have had to be explained in

4554-492: The volcano. Solid particles smaller than 2 mm in diameter ( sand-sized or smaller) are called volcanic ash. Tephra and other volcaniclastics (shattered volcanic material) make up more of the volume of many volcanoes than do lava flows. Volcaniclastics may have contributed as much as a third of all sedimentation in the geologic record. The production of large volumes of tephra is characteristic of explosive volcanism. Through natural processes, mainly erosion , so much of

4623-424: The volcanoes of the East African Rift . A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice , typically a volcanic cone or mountain. The most common perception of

4692-421: Was described by Roman writers as having been covered with gardens and vineyards before its unexpected eruption of 79 CE , which destroyed the towns of Herculaneum and Pompeii . Accordingly, it can sometimes be difficult to distinguish between an extinct volcano and a dormant (inactive) one. Long volcano dormancy is known to decrease awareness. Pinatubo was an inconspicuous volcano, unknown to most people in

4761-601: Was in the territory of Troezen . In his History of the Peloponnesian War , Thucydides tells of an Athenian expeditionary force under Nicias that after defeating Corinth (in 425 BC) built a wall across the isthmus to cut the Methana peninsula off from the mainland. In the Hellenistic period, the peninsula became one of the Ptolemaic bases in the Aegean when it was renamed Arsinoe. When Pausanias visited in

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