The longest axis of the island runs approximately 1,790 km (1,110 mi) northwest�southeast, crossing the equator near the centre. At its widest point, the island spans 435 km (270 mi). The interior of the island is dominated by two geographical regions: the Barisan Mountains in the west and swampy plains in the east.
To the southeast is Java, separated by the Sunda Strait. To the north is the Malay Peninsula, separated by the Strait of Malacca. To the east is Borneo, across the Karimata Strait. West of the island is the Indian Ocean.
The backbone of the island is the Barisan Mountain chain, with the active volcano Mount Kerinci as the highest point at 3,805 m (12,467 ft), located at about the midpoint of the range. The volcanic activity of this region endowed the region with fertile land and beautiful sceneries, for instance around Lake Toba. It also contains deposits of coal and gold. The volcanic activity stems from Sumatra's location on the Pacific "Ring of Fire"�which is also the reason why Sumatra has had some of the most powerful earthquakes ever recorded: in 1833, 2004, 2005 and in the September 2007 Sumatra earthquakes.
To the east, big rivers carry silt from the mountains, forming the vast lowland interspersed by swamps. Even if mostly unsuitable for farming, the area is currently of great economic importance for Indonesia. It produces oil from both above and below the soil�palm oil and petroleum.
Sumatra is the largest producer of Indonesian coffee. Small-holders grow Arabica coffee (Coffea arabica) in the highlands, while Robusta (Coffea canephora) is found in the lowlands. Arabica coffee from the regions of Gayo, Lintong and Sidikilang is typically processed using the Giling Basah (wet hulling) technique, which gives it a heavy body and low acidity.
Most of Sumatra used to be covered by tropical rainforest, but economic development coupled with corruption and illegal logging has severely threatened its existence. Even
