KRAKATAU, INDONESIA (1883)

OVERVIEW

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. 

Merapi Volcano Overview & Recent Activity

Introduction

Merapi volcano is situated above the subduction zone between the Eurasian and Indo-Australian tectonic plates. This subduction extends for about 2000 km from Sumatra to the Lesser Sunda Islands. In the Java-Bali sector, subduction occurs between an oceanic plate 10-km in thickness (Indo-Australian) and an intermediate plate of 20-km thickness (Eurasian). This Mesozoic subduction has formed a trench of 6 to 7 km deep.

Mount Merapi

Mount Merapi

Gunung Merapi (literally Mountain of Fire in Indonesian/Javanese), is a conical volcano located on the border between Central Java and Yogyakarta, Indonesia. It is the most active volcano in Indonesia and has erupted regularly since 1548. It is very close to the city of Yogyakarta, and thousands of people live on the flanks of the volcano, with villages as high as 1700 m above sea level.

 The name Merapi could be loosely translated as 'Mountain of Fire' from the Javanese combined words; Meru means "mountain" and api means "fire". Smoke can be seen emerging from the mountaintop at least 300 days a year, and several eruptions have caused fatalities. Hot gas from a large explosion killed 27 people on November 22 in 1994, mostly in the town of Muntilan, west of the volcano. Another large eruption occurred in 2006, shortly before the Yogyakarta earthquake. In light of the hazards that Merapi poses to populated areas, it has been designated as one of the Decade Volcanoes.

Kecepatan Luncur Wedus Gembel

Wedhus gembel atau awan panas Gunung Merapi mencapai 600 derajat celcius. Awan panas itu mengandung bermacam-macam material berupa berupa batu, kerikil, pasir, abu dan gas vulkanik. Material itu meluncur mengikuti morfologi lereng dan gas vulkanik yang bertekanan tinggi bergerak secara turbulen.

“Luncuran kencang itu karena tekanan gas sangat kuat, kecepatannya mencapai 300 kilometer per jam,” kata IGM Agung Nandaka, Kepala Seksi Metode dan Teknologi Mitigasi Balai Penyelidikan dan Pengembangan Teknologi Kegunungapian (BPTTK) Yoyakarta, Rabu (27/10).

Abu Vulkanik Pedih di Mata

Abu Vulkanik

Secara geologis, abu vulkanik adalah material batuan vulkanik yang berasal dari magma panas dan cair yg membeku secara cepat. Batuan beku sejatinya kumpulan mineral yang membeku dan mengkristal dari magma cair. Karena membeku cepat maka magma ini tidak sempat mengkristal dengan baik. Karena tidak mengkristal dalam geologi material bekuannya disebut gelas. Ya mirip gelas kaca yang kita pakai itu.

Bahaya Abu Vulkanik

Abu vulkanik yang keluar dari letusan gunung merapai dapat membahayakan bagi masyarakat yang tinggal di sekitar lereng gunung merapi. Erupsi (fenomena keluarnya magma dari dalam bumi) gunung merapi akan menjadi ancaman bagi warga disekitar lereng gunung. Tak hanya gumpalan awan panas yang mematikan, tapi juga abu vulkanik yang sangat berbahaya bagi kesehatan.

Types of water pollution

Types of water pollution

Water pollution is usually caused by human activities. Different human sources add to the pollution of water. There are two sorts of sources, point and nonpoint sources. Point sources discharge pollutants at specific locations through pipelines or sewers into the surface water. Nonpoint sources are sources that cannot be traced to a single site of discharge.

Examples of point sources are: factories, sewage treatment plants, underground mines, oil wells, oil tankers and agriculture. Examples of nonpoint sources are: acid deposition from the air, traffic, pollutants that are spread through rivers and pollutants that enter the water through groundwater. Nonpoint pollution is hard to control because the perpetrators cannot be traced.(Mariz_08-06)

 

Air Pollution

Air Pollution

Every day, the average person inhales about 20,000 liters of air.  Every time we breathe, we risk inhaling dangerous chemicals that have found their way into the air.

Air pollution includes all contaminants found in the atmosphere.  These dangerous substances can be either in the form of gases or particles.