Earth Observatory Blog

Submitted on 05 May 2017 by:

Different rainforest trees grow on an island called Siberut; one of four big islands of the Mentawai Archipelago located off the west coast of Sumatra, Indonesia. Katuka is what Mentawaians call one family of these dipterocarp trees. These trees have very hard wood and are widely used for construction and crafting.

I want to tell you the story of one katuka tree in particular. This 400-year-old tree will soon surrender its life to serve the needs of the people. 

A Giant Falls

As the sun rises over Siberut Island, a Mentawaian called Aman Ani and his fellow villagers sharpen their axes. They prepare their meals, as well as an offering for the forest spirits. Later, they sit quietly in a motorised canoe as they cruise upstream. Some of them are...

Submitted on 13 Jun 2016 by:

Sinabung volcano in Sumatra, Indonesia, has been almost continuously erupting in the last three years. It has been on the highest alert level since 2013. 

Most of the eruptions on Mount Sinabung have been small. These eruptions vary between lava flows and dome extrusions that accumulate on the volcanic crater, and include explosions with ash plumes that are lower than 3 kilometres (km) in height.

The most common activity on the volcano are the pyroclastic flows that are generated by the gravitational collapse of the dome rocks that have gathered on the summit. The travel distance of these pyroclastic flows range from 2 km to 5 km. As such, since 2014, the exclusion zones were appropriately implemented up to 7 km of the south (S) sector and 6 km southeast-east (SE-E) of...

Submitted on 09 Jun 2016 by:

A magnitude-6.2 earthquake occurred about 300 km southeast of Bali Island on 9 June 2016 at approximately 12.13pm (Singapore Time). Its epicentre is estimated to be close to the Java Trench front with a shallow focal depth from the global seismic network.

Although the tremors from this earthquake were felt by people in Bali and eastern Java, more than 400 km from the epicentre, it is not likely that this earthquake will generate a major tsunami event in Indonesia based on the current estimation of its magnitude.

The Java Trench is located at the southeastern extension of the Sunda Trench, where the Australian plate subducts beneath other tectonic plates along Java and the Lesser Sunda Island. In the past century, the Java Trench has produced more than four major...

Submitted on 20 Apr 2016 by:

Japan is known for its earthquakes and tsunami hazards due to the active collision involving three tectonic plates; the Philippine Sea plate, the Pacific plate and the Eurasian plate. These plate convergences not only created the giant trench system found off the eastern Japanese coastline, they also generated a series of active inland faults close to densely populated cities like Osaka, Nagoya, and Tokyo (Fig. 1).

Active faults found on land are usually shorter in length, and move more slowly than those found under the sea in the giant subduction zone where tectonic plates meet. The earthquakes generated by these inland faults are infrequent, and often smaller in magnitude and intensity than the earthquakes in the offshore subduction zone. However, because these inland...