Earth from Space: Bromo volcano, East Java

Indonesia is located within the Pacific 'Ring of Fire' volcano belt and has more than a hundred active volcanoes within its territory. With around 200 million inhabitants, Java is the most populated island in Indonesia and also the world. The island was formed by ancient volcanic activity.

Bromo is one of Java's most active volcanoes, located on top of the 16-kilometre-wide Tenegger Caldera in East Java, with a summit elevation of 2329 metres. The Caldera is part of Bromo Tengger Semeru National Park, situated about 112 km southeast of the East Java capital of Surabaya.

The volcano itself is the youngest of the cones at the centre of the Tenegger Caldera. It stands 133 metres above the lunar-like landscape of the Caldera and is 700 metres wide. The smaller, ribbed cone just north of it is the Batok volcano.

While Batok is no longer active, the same is not true of Bromo: the volcano has erupted at least 50 times since 1775 and last erupted in June 2004. Its ash cloud reached 3000 metres above the crater rim and stones rained down around the crater to a distance of about two kilometres away. Two visitors were killed and five more left injured by the volcanic activity.

Indonesian seismologists estimate that there is a magma chamber buried about a kilometre under the caldera floor, responsible for periodic inflation and deflation events monitored by GPS and levelling techniques.

Even in normally active conditions, Bromo still produces volcanic gases including the tasteless and odourless but also poisonous 'mofet' gas made up of carbon monoxide and dioxide.

Nevertheless, Bromo is one of the most frequently visited attractions in East Java. The volcano is noted for spectacular sunrises and expansive views across to Semuru volcano to the south. Visitors often cross the caldera floor on horseback.

This is a detail from a 19 June 2004 image acquired by the Compact High Resolution Imaging Spectrometer (CHRIS). Built by UK-based Sira Technology, CHRIS is the main payload on ESA's Proba microsatellite, designed to acquire hyperspectral images with a spatial resolution of 18 metres across an area of 14 kilometres.

The size of a washing machine, Proba was originally launched in 2001 as a technology demonstrator, but is now operated as an ESA Earth Observation Third Party Mission.