Merapi Eruption

The eruption of Mount Merapi in Central Java and Yogyakarta border on Tuesday was not much when compared with previous eruptions.

The eruption in 1930 killed at least 1370 people in 13 villages on the slopes of Merapi. But this is not the biggest eruption. Precisely the largest eruption occurred in 1006. At that time covered the whole of Java volcanic ash. Unfortunately not known how many victims of the eruption.

Based on the records of Volcanology and Geological Hazard Mitigation, Ministry of Energy and Mineral Resources, the first eruption of Mount Merapi experienced in 1006. Average Merapi erupted in a short cycle of 2-5 years, and secondary cycles every 5-7 years.

The longest cycle ever recorded after a break for more than 30 years, ie during the initial formation of an active volcano. Entering the 16th century, the longest cycle Merapi is a 71 year gap from 1587 to 1658 eruption.

Volcanology noted, a large eruption of Merapi occurred in 1006, 1786, 1822, 1872, and 1930. Previous eruption occurred four years ago, precisely on June 8, 2006 at 09:03.

When the government to evacuate 17 thousand people on the slopes of Merapi. However, two people sheltering in a bunker in Area Tourism Kaliadem, Kaliurang, just roasting hot clouds. Bunker could not protect the victim from wedhus gembel the temperature is still 500-600 degrees Celsius.

Tuesday afternoon, October 26, Merapi erupted again. The first eruption of Mount Merapi occurred since at 17:02 pm, followed by hot clouds for 9 minutes. Then repeated until the last eruption at 18:21 that cause hot clouds for 33 minutes.

This hot cloud has devastated several villages on the slopes of Merapi. At least 30 people died on the scene

KRAKATAU, INDONESIA (1883)

Early in the morning of May 20, 1883, the captain of the German warship Elizabeth reported seeing an ~11-km-high cloud of ash and dust rising above the uninhabited island of Krakatau, thus documenting the first eruption from this Indonesian island in at least two centures. Over the ensuing two months, crews on commercial vessels and sightseers on charted ships would experience similar spectacles, all of which were associated with explosive noises and churning clouds of black to incandescent ash and pumice. From a distance, the largest of these natural fanfares impressed the local inhabitants on the coastal plains of Java and Sumatra, creating a near-festive environment. Little did they realize, however, that these awe-inspiring displays were only a prelude to one of the largest eruptions in historic times. A series of cataclysmic explosions began at mid-day on August 26, and ended on August 27 with a stupendous paroxysmal eruption. On this day, the northern two-thirds of the island collapsed beneath the sea, generating a series of devasting pyroclastic flows and immense tsunamis that ravaged adjacent coastlines. The events that began on August 26 would mark the last 24 hours on earth for over 36,000 people, and the destruction of hundreds of coastal villages and towns.

 

LOCATION AND PLATE-TECTONIC SETTING

Indonesia contains over 130 active volcanoes, more than any other country on earth. They comprise the axis of the Indonesian island arc system, which is generated by northeastward subduction of the Indo-Australian plate. The great majority of these volcanoes lie along the topographic crest of the arc's two largest islands - Java and Sumatra. The islands are separated by the Sunda Straits, which is located at a distinct bend in axis of the island arc volcanoes, from a nearly east-west orientation in Java to a northwest-southeast orientation in Sumatra. Krakatau is one of a several volcanic islands in the Sunda Straits located above an active north-northeast trending fault zone, an orientation quite distinct from the main island-arc trend. Although relatively small when compared to the largest volcanoes along the island arc, Krakatau and its associated volcanoes have shown the capacity to generate highly explosive eruptions

 

PHYSIOGRAPHY BEFORE AND AFTER THE 1883 ERUPTION

The pre-eruption island of Kratatau was composed of three coalsced volcanoes aligned along a north-northwest direction, parallel to the volcanoes on Sumatra. From north to south, these were Perboewatan, Danan, and Rakata.

During the eruption, Perboewatan, Danan, and the northern half of Rakata appear to have collapsed into the vacating magma chamber, thus forming a submarine caldera and destroying the northern two-thirds of the island. Some workers, however, have argued for an alternative to the caldron-collapse model, and instead have suggested that the caldera formed by explosive destruction of the island, and the reaming out of the pre-eruption edifice. Eruptions since 1927 have built a new cone called Anak Krakatau ("child of Krakatau") in the center of the 1883 caldera.

 

 

Vulcano Mythology

The Ancient Greeks named the island Therassía (Θηρασία) and Thérmessa (Θέρμεσσα, source of heat). The island appeared in their myths as the private workshop of the Olympian god Hephaestus, protector of the blacksmiths; he owned another two at Etna and Olympus. Strabo also mentions Thermessa as sacred place of Hephaestus (ἱερὰ Ἡφαίστου), but it's not clear if it was a third name for the island, or just an adjective.[1]

Similarily the Romans believed that Vulcano was the chimney to the god Vulcanus's workshop. The island had grown due to his periodic clearing of cinders and ashes from his forge. The earthquakes that either preceded or accompanied the explosions of ash etc., were considered to be due to Vulcanus making weapons for Mars and his armies to wage war. [2]

Since Roman times similar features on Earth have been known as volcans, volcanes and volcanoes. It is also used in connection with similar features on the Moon, Mars, Venus, Mercury and other solar system bodies.

History Of Volcano

 The Roman name for the island Vulcano has contributed the word for volcano in most modern European languages. The Romans used the island mainly for raw materials, harvesting wood and mining alum and sulfur. This was the principal activity on the island until the end of the 19th Century.

When the Bourbon rule collapsed in 1860 (see Francis II of the Two Sicilies) a British man named James Stevenson bought the northern part of the island, built a villa, reopened the local mines and planted vineyards for grapes that would later be used to make Malmsey wine. Stevenson lived on Vulcano until the last major eruption on the island, in 1888. The eruption lasted the better part of two years, by which time Stevenson had sold all of his property to the local populace, and never returned to the island. The villa is still intact.

Currently, around 470 people live on the island, mainly deriving their income from tourism. It is a few minutes hydrofoil ride from Lipari and has several hotels and cafes, the important attractions being the beaches, hot springs and sulfur mud baths.

The volcanic activity in the region is largely the result of the northward-moving African Plate meeting the Eurasian Plate. There are three volcanic centres on the island:

    * At the southern end of the island are old stratovolcano cones, Monte Aria (501 m), Monte Saraceno (481 m) and Monte Luccia (188 m), which have partially collapsed into the Il Piano Caldera.
    * The most recently active centre is the Gran Cratere at the top of the Fossa cone, the cone having grown in the Lentia Caldera in the middle of the island, and has had at least 7 major eruptions in the last 6000 years.
    * At the north of the island is Vulcanello, 123 metres high, and is connected to the rest of it by an isthmus which is flooded in bad weather. It emerged from the sea during an eruption in 183 BC as a separate islet. Occasional eruptions from its three cones with both pyroclastic flow deposits and lavas occurred from then until 1550, the last eruption creating a narrow isthmus connecting it to Vulcano.

Vulcano has been quiet since the eruption of the Fossa cone on 3 August 1888 to 1890, which deposited about 5 metres of pyroclastic material on the summit. The style of eruption seen on the Fossa cone is called a Vulcanian eruption, being the explosive emission of pyroclastic fragments of viscous magmas caused by the high viscosity preventing gases from escaping easily. This eruption of Vulcano was carefully documented at the time by Giuseppe Mercalli.