User:Cherin105/Sunda Arc

The Sunda Arc is a volcanic arc that produced the volcanoes that form the topographic spine of the islands of Sumatra, Nusa Tenggara, and 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].

Formation and Geologic Setting

Mid-oceanic ridge basalts

Tsunami on December 2004, Indian Ocean

In 2004, the tsunami in Indian Ocean was triggered by an earthquake of 9.15 magnitude near Sumatra Island^[10]. In Banda Aceh area, the tsunami height reached up to 35 meters, which surpassed value recorded prior to this event^[11].

Tsunami on July 2006, West Java and Central Java, Indonesia

Another devastating events also occurred on July 17, 2006 with major destruction along West Java and Central Java. The M_w-7.7 earthquake-induced tsunami struck over 250 km of the coastline and cost more than 600 deaths. The approximate run-up height was about 4-6 meters^[12].

Historic Eruptions and Arc Volcanisms

[Historic Eruption part is already up in the actual page by previous writers]

Main-Arc Volcanism

The main-arc volcanism along Sunda is mainly derived from the interaction between the

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 part of Sunda Arc [3]^[13]. Most salient volcanoes in back-arc region are Lasem, Muria, and Bawean in which their volcanic rocks show complex patterns in terms of chemical signature^[3].

Major Islands

Java

Java Island is located on the east side of Sunda Arc, residing between Sumatra and Bali^[15]. Its oceanic crust's thickness is approximately 20-25 kilometers^[13]. With the geological activities and the tectonic nature of Sunda Arc, megathrust earthquakes and volcanic activities are ubiquitous at Java island^[16]. Modern volcanoes at Java are formed during Tertiary with typical products of andesitic composition and progressively get more alkali content during Quaternary^[13][17]. Along the Java island, there are approximately 62 geothermal fields which can be utilized for further usages including producing electricity^[18]. Java is also a germinal center for supplying gold and cooper in which the occurrences of these low-sulfidication (LS) epithermal deposits may associate with magmatic arc activities^[15] with the spatial relationship between the akaditic magma and porphyry Cu-Au deposits^[19][20].

East Java

Most volcanic activties at East Java are Plinian-type which is very explosive and emits column of hot volcanic debris^[21]. The adiakitic magma, which deviates from usual island-arc magma, is associated to porphyry deposits that present on East Java^[19]. There were also evidences that the Ringgit-Beser volcanic complex also produces potassic and magnesian lava, which could be a result from the decreasing influence of subduction-related material^[22]. Some major volcanoes at East Java are Mount Bromo and Krakatoa.

Krakatoa: The island of Anak Krakatau has grown at an average rate of five inches (13 cm) per week since the 1950s. Quiet periods of a few days have alternated with almost continuous Strombolian eruptions since 1994. In 1883 CE, tsunami were triggered by the eruption of Krakatoa with the run-up of 41 meters^[23]. The magnitude of damage reached Panama, which was located almost 19,300 km away from the focus^[23].

Central Java

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^[16]. Prior studies suggested that SMA is formed during Middle Eocene^[24], followed by the subduction that resulted in the formation of MVA in Late Eocene^[25][16]. 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 erupt periodically every 2-6 years^[26]and has shown perenial volcanic activities dated back roughly 2000 years ago based on carbon isotropic signatures^[27]. The earliest eruption has been approximated to be roughly 40,000 years ago^[28]. The most recent significant eruptions occurred in 1994, 2006, and 2010. Mount Merapi is a steep stratovocano situated on Central Java Island with its seismic and volcanic activities that could pose major threats to countless lives and infrastructures in its vicinity.^[29] Most recent volcanic activities are induced by the collapse of lava dome, contributing to highly explosive eruption of andesitic materials^[29][30].

West Java

The volcanic activities in this region have began roughly since

Sumatra

Sumatra island is located on the southwest side of Sunda Arc^[37]. The main seismic zone of Sumatra is the Sumatra Fault System (SFS), which trends NW-SE^[37]. The subducting oceanic crust are dated to be approximately 50 to 90 Ma^[6]. A K/Ar study reveals that subducted-related magmatism in Sumatra started roughly in early Mesozoic according to the evidences derived from the plutonic body on Barisan Mountain ^[38][37][39]. The key mineralization found on Sumatra are epithermal veins of Au, Ag, Zn, Pb, and other metals in which these ore bodies are correlated to arc volcanism and subvolcanism intrusive bodies^[40].

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

Nusa Tenggara lies at the east side of Sunda. The information and study on this island were scarce comparing to Java due to the difficulty to access^[1]. Generally, the island is composed on Quaternary volcanic deposits^[1]. Major volcanoes in Nusa Tenggara are Kelimutu and Mount Rinjani. Seismic studies have shown clusters of seismic events beneath active island-arc volcanoes, which may be a result from the collision zone^[41][42].