Geography | |
---|---|
Location | Indonesia |
Coordinates | 7°09′04″S110°08′25″E / 7.1510°S 110.1403°E |
Major islands | Sumatra, Java, Nusa Tenggara |
Additional information | |
Tectonic - Indo-Australian Plate and Eurasia Plate Major Volcanoes - Merapi, Krakatoa, Mount Sinabung, Semeru |
The Sunda Arc is a volcanic arc that produced the volcanoes that form the topographic spine of the islands of Sumatra, Nusa Tenggara, Java, the Sunda Strait, and the Lesser Sunda Islands. The Sunda Arc begins at Sumatra and ends at Flores, and is adjacent to the Banda Arc. [1] The Sunda Arc is formed via the subduction of the Indo-Australian Plate beneath the Sunda and Burma plates at a velocity of 63–70 mm/year. [2]
Mid-oceanic ridge basalts (MORB) form most of the oceanic basin south of Sunda, according to geodynamic studies. [3] These plates began to converge in the Early Miocene. [3] The Indo-Australian Plate is subducting beneath the Eurasian Plate with a dip angle of 49-56 degrees. [4] The slab subducting under Java is continuous down to the lower mantle. However, the slab appears to beak apart under Sumatra Island . [5] [6] Earthquake depth records indicate that there is no deep seismic activity in Sumatra, likely due to the age of the subducting complex. [7] [6] [8] Two types of subductions have been identified along the Sunda Arc: 1) orthogonal subduction along Java and 2) oblique subduction on the Sumatra side. These subductions are separated by the Sunda Strait. [9]
With the ongoing magmatic activities and the nature of the subduction zone, Sunda Arc has experienced major seismic events throughout history. These events cost the loss of lives and vast destruction along the coast. These are some major seismic events that have been recorded.
In 2004, the tsunami in the Indian Ocean was triggered by an earthquake of 9.15 magnitude near Sumatra Island. [10] In the Banda Aceh area, the tsunami height reached up to 35 meters, which surpassed the value recorded before this event. [11]
A devastating event occurred on July 17, 2006, with major destruction along West Java and Central Java. The Mw-7.7 earthquake-induced tsunami struck over 250 km of the coastline and caused more than 600 deaths. The approximate run-up height was about 4–6 meters. [12]
The Sunda Arc is home to some of the world's most dangerous and explosive volcanoes. [13] The 1815 eruption of Mount Tambora on Sumbawa and the 1257 eruption of Mount Samalas on Lombok were among the largest in the last two millennia, ranking 7 on the VEI scale. [14] The Sunda Arc subduction zone was also the site of one of the largest known eruptions of the Cenozoic, the VEI 8 Toba supereruption on Sumatra, which expelled 2,800 km³ of magma c. 74,000 BP. [15] The resulting caldera has become Lake Toba. The loudest noise in recorded history occurred during the 1883 eruption of Krakatoa and was heard 5,000 km (3,100 mi) away. [16] Hundreds of thousands of people have been killed by these eruptions and by episodes of activity at other volcanoes, including Papandayan, Galunggung, Merapi, Kelud, Sinabung, and Agung.
The main-arc volcanism along Sunda is mainly derived from the interaction between the Indo-Australian Plate and the Eurasia Plate. Magma originates from the partial melting of the mantle wedge driven by the fluids from the subducting slab. [17] In addition, volcanic rocks from the Quaternary generally show more enrichment in alkaline contents than those from the Tertiary age. [17] [13] The majority of basalts of the arc have calc-alkaline contents, except for some potassic lava production in East Java. [18]
The magmatic activities along the back-arc may or may not relate to the main arc materials. Magma and lava appear to have originated from molten materials at a deeper part of the mantle as supported by a higher K2O/Na2O ratio in comparison to other parts of Sunda Arc. [3] [17] The most salient volcanoes in the back-arc region are Lasem, Muria, and Bawean in which their volcanic rocks show complex patterns in terms of chemical signature. [3]
Java Island is located on the east side of the Sunda Arc, located between Sumatra and Bali. [19] Its oceanic crust's thickness is approximately 20-25 kilometers. [17] With the geological activities and the tectonic nature of Sunda Arc, megathrust earthquakes and volcanic activities are ubiquitous on Java island. [20] Modern volcanoes at Java are formed during the Tertiary with typical products of andesitic composition and progressively get more alkali content during the Quaternary. [17] [21] Along the Java island, there are approximately 62 geothermal fields that can be utilized for further usages including producing electricity. [22] Java is also a germinal center for supplying gold and cooper in which the occurrences of these low-sulfidation (LS) epithermal deposits may associate with magmatic arc activities [19] with the spatial relationship between the akaditic magma and porphyry Cu-Au deposits. [23] [24]
Most volcanic activity in East Java is Plinian-type, which is very explosive and emits columns of hot volcanic debris. [25] The adiakitic magma, which deviates from usual island-arc magma, is associated with porphyry deposits. [23] There is evidence that the Ringgit-Beser volcanic complex also produces potassic and magnesian lava, which could be a result of the decreasing influence of subduction-related material. [26] A major volcano in East Java is Mount Bromo.
There exist two main arcs at Central Java which are Southern Mountain Arc (SMA) and Modern Volcanic Arc (MVA) which give rise to frequent volcanic activities. [20] Prior studies suggested that SMA was formed during the Middle Eocene, [27] followed by the subduction that resulted in the formation of MVA in the Late Eocene. [28] [20] Central Java is home to one of the most notorious volcanoes, Merapi, as well as other major volcanoes such as Merbabu, Muria, and Slamet.
Mount Merapi is the most active volcano in Indonesia which erupts periodically every 2–6 years [29] and has shown perennial volcanic activities dating back roughly 2000 years ago based on carbon isotopic signatures. [30] The earliest eruption has been approximated to be roughly 40,000 years ago. [31] The most recent significant eruptions occurred in 1994, 2006, and 2010. Mount Merapi is a steep stratovolcano situated on Central Java Island with seismic and volcanic activities that could pose major threats to countless lives and infrastructures in its vicinity. [32] Most recent volcanic activities are induced by the collapse of the lava dome, contributing to the highly explosive eruption of andesitic materials. [32] [33]
The volcanic activities in this region have begun roughly since the Late Cretaceous or Pleistocene epoch. [34] [35] There are two major volcanic zones called the volcanic front (VF) and the rear arc (RA) with different chemical imprints. [36] The volcanic development of the northern area of West Java started earlier during the Late Cretaceous period, while the southern area's volcanic development developed later during the Miocene. [37] The geochemical study of major and trace elements and isotopic signatures of lava have confirmed the steady-state subduction and ongoing replenishment of magma for about 10 Ma. [36] The volcanic rocks found on West Java are dated back to the Eocene. [36] The basement of West Java is a continental lithosphere which can be inferred from crustal assimilation and contamination in volcanic rocks. [38] [39] The latest large eruption recorded in the province was the 1982 eruption of Mount Galunggung, with a recorded VEI of 4. [40]
The island of Anak Krakatau has grown at an average rate of five inches (13 cm) per week since the 1950s. [41] Quiet periods of a few days have alternated with almost continuous Strombolian eruptions since 1994. In 1883 CE, tsunamis were triggered by the eruption of Krakatoa with a run-up of 41 meters. [42] The magnitude of damage reached Panama, which was located almost 19,300 km away from the focus. [42]
Sumatra Island is located on the southwest side of the Sunda Arc. [43] The main seismic zone of Sumatra is the Sumatra Fault System (SFS), which trends NW-SE. [43] The subducting oceanic crust is dated to be approximately 50 to 90 Ma. [6] A K/Ar study reveals that subducted-related magmatism in Sumatra started roughly in the early Mesozoic according to the evidence derived from the plutonic body on Barisan Mountain. [44] [43] [45] The key mineralization found in Sumatra is epithermal veins of Au, Ag, Zn, Pb, and other metals in which these ore bodies are correlated to arc volcanism and subvolcanism intrusive bodies. [46]
Mount Sinabung is a stratovolcano of andesite and dacite in the Karo plateau of North Sumatra, 40 kilometres (25 mi) from the Lake Toba supervolcano. It has been continuously active since 2013.
Nusa Tenggara lies on the east side of the Sunda Arc. The information and study on this island are scarce compared to Java due to the difficulty of access. [1] Generally, the island is composed of Quaternary volcanic deposits. [1] Major volcanoes in Nusa Tenggara are Kelimutu and Mount Rinjani. Another active major volcano in the region is Mount Tambora, whose eruption in 1815 led to global climate abnormalities in the subsequent year, known as the Year Without a Summer. Seismic studies have shown clusters of seismic events beneath active island-arc volcanoes, which may be a result of the collision zone. [47] [48]
Lake Toba is a large natural lake in North Sumatra, Indonesia, occupying the caldera of a supervolcano. The lake is located in the middle of the northern part of the island of Sumatra, with a surface elevation of about 900 metres (2,953 ft), the lake stretches from 2.88°N 98.52°E to 2.35°N 99.1°E. The lake is about 100 kilometres long, 30 kilometres (19 mi) wide, and up to 505 metres (1,657 ft) deep. It is the largest lake in Indonesia and the largest volcanic lake in the world. Toba Caldera is one of twenty geoparks in Indonesia, and was recognised in July 2020 as one of the UNESCO Global Geoparks.
A supervolcano is a volcano that has had an eruption with a volcanic explosivity index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for such an eruption is greater than 1,000 cubic kilometers.
Mount Tambora, or Tomboro, is an active stratovolcano in West Nusa Tenggara, Indonesia. Located on Sumbawa in the Lesser Sunda Islands, it was formed by the active subduction zones beneath it. Before 1815, its elevation reached more than 4,300 metres high, making it one of the tallest peaks in the Indonesian archipelago.
The Ring of Fire is a tectonic belt of volcanoes and earthquakes, about 40,000 km (25,000 mi) long and up to about 500 km (310 mi) wide, which surrounds most of the Pacific Ocean. The exact number of volcanoes within the Ring of Fire is not universally agreed but, depending on which regions are included in any particular count, it contains between 750 and 915 active or dormant volcanoes, around two-thirds of the world total. About 90% of the world's earthquakes, including most of its largest, occur within the belt.
The Taupō Volcanic Zone (TVZ) is a volcanic area in the North Island of New Zealand that has been active for at least the past two million years and is still highly active. Mount Ruapehu marks its south-western end and the zone runs north-eastward through the Taupō and Rotorua areas and offshore into the Bay of Plenty. It is part of the larger Central Volcanic Region that extends further westward through the western Bay of Plenty to the eastern side of the Coromandel Peninsula and has been active for four million years. At Taupō the rift volcanic zone is widening east–west at the rate of about 8 mm per year while at Mount Ruapehu it is only 2–4 mm per year but this increases at the north eastern end at the Bay of Plenty coast to 10–15 mm per year. It is named after Lake Taupō, the flooded caldera of the largest volcano in the zone, the Taupō Volcano and contains a large central volcanic plateau as well as other landforms associated with its containing tectonic intra-arc continental Taupō Rift.
Andesite is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.
A xenolith is a rock fragment that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock entrained during magma ascent, emplacement and eruption. Xenoliths may be engulfed along the margins of a magma chamber, torn loose from the walls of an erupting lava conduit or explosive diatreme or picked up along the base of a flowing body of lava on the Earth's surface. A xenocryst is an individual foreign crystal included within an igneous body. Examples of xenocrysts are quartz crystals in a silica-deficient lava and diamonds within kimberlite diatremes. Xenoliths can be non-uniform within individual locations, even in areas which are spatially limited, e.g. rhyolite-dominated lava of Niijima volcano (Japan) contains two types of gabbroic xenoliths which are of different origin - they were formed in different temperature and pressure conditions.
A volcano tectonic earthquake or volcano earthquake is caused by the movement of magma beneath the surface of the Earth. The movement results in pressure changes where the rock around the magma has a change in stress. At some point, this stress can cause the rock to break or move. This seismic activity is used by scientists to monitor volcanoes. The earthquakes may also be related to dike intrusion and/or occur as earthquake swarms. Usually they are characterised by high seismic frequency and lack the pattern of a main shock followed by a decaying aftershock distribution of fault related tectonic earthquakes.
A volcanic arc is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc located further from the subducting plate than the trench. The oceanic plate is saturated with water, mostly in the form of hydrous minerals such as micas, amphiboles, and serpentines. As the oceanic plate is subducted, it is subjected to increasing pressure and temperature with increasing depth. The heat and pressure break down the hydrous minerals in the plate, releasing water into the overlying mantle. Volatiles such as water drastically lower the melting point of the mantle, causing some of the mantle to melt and form magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone.
Plinian eruptions or Vesuvian eruptions are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a letter written by Pliny the Younger, after the death of his uncle Pliny the Elder.
Bazman is a dormant stratovolcano in a remote desert region of Sistan and Baluchestan Province in southeastern Iran. A 500-m-wide crater caps the summit of the dominantly andesitic-dacitic volcano, the flanks of which are covered by monogenetic centres especially to the northwest. Bazman is a geologically young volcano which formed mainly in the Quaternary, with the oldest dated rocks being 11.7 million years old and the youngest 0.6 million years. Although no historic eruptions have been reported from Bazman, it does contain fumaroles. Thus Bazman may be regarded as dormant, rather than extinct, volcano. Its satellite cones have been the source of basaltic lava flows.
Cerro del Azufre is a stratovolcano located in El Loa Province, Antofagasta Region, Chile. It is part of a chain of volcanoes that separate Upper Loa River basin from Salar de Ascotán basin and is flanked to the west by a dacitic lava dome called Chanka or Pabellón. The 6000 metre volcanoes San Pedro and San Pablo are located to the southwest of Cerro del Azufre.
The volcanism of New Zealand has been responsible for many of the country's geographical features, especially in the North Island and the country's outlying islands.
La Pacana is a Miocene age caldera in northern Chile's Antofagasta Region. Part of the Central Volcanic Zone of the Andes, it is part of the Altiplano-Puna volcanic complex, a major caldera and silicic ignimbrite volcanic field. This volcanic field is located in remote regions at the Zapaleri tripoint between Chile, Bolivia and Argentina.
The Altiplano–Puna volcanic complex, also known as APVC, is a complex of volcanic systems in the Puna of the Andes. It is located in the Altiplano area, a highland bounded by the Bolivian Cordillera Real in the east and by the main chain of the Andes, the Western Cordillera, in the west. It results from the subduction of the Nazca Plate beneath the South American Plate. Melts caused by subduction have generated the volcanoes of the Andean Volcanic Belt including the APVC. The volcanic province is located between 21° S–24° S latitude. The APVC spans the countries of Argentina, Bolivia and Chile.
The magma supply rate measures the production rate of magma at a volcano. Global magma production rates on Earth are about 20–25 cubic kilometres per year (4.8–6.0 cu mi/a).
Panizos is a Late Miocene caldera in the Potosí Department of Bolivia and the Jujuy Province of Argentina. It is part of the Altiplano-Puna volcanic complex of the Central Volcanic Zone in the Andes. 50 volcanoes active in recent times are found in the Central Volcanic Zone, and several major caldera complexes are situated in the area. The caldera is located in a difficult-to-access part of the Andes.
The Deep Earth Carbon Degassing (DECADE) project is an initiative to unite scientists around the world to make tangible advances towards quantifying the amount of carbon outgassed from the Earth's deep interior into the surface environment through naturally occurring processes. DECADE is an initiative within the Deep Carbon Observatory (DCO).
Pica gap is a segment in the Central Volcanic Zone of Chile where volcanic activity is absent. It is named after the Altos de Pica region.
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