Idjwi or Ijwi Island is located in Lake Kivu in the Sud-Kivu province of the Democratic Republic of the Congo. At 70 km in length and with an area of 340 km², it is the second largest inland island in Africa, and the tenth largest in the world. Idjwi is roughly equidistant between the Democratic Republic of the Congo and Rwanda, with 10 to 15 kilometers separating its western shore from the Congo mainland and a similar distance between its eastern shore and the coastline of Rwanda. The island's southern tip, however, lies only 1 kilometer from a promontory of the Rwandan coast.
Historically a clan-based society, Idjwi Island became a kingdom in the late 18th century (roughly between 1780 and 1840) under the influence of the neighboring Kingdom of Rwanda.
In 2009 the island was estimated to have a population of 203,000. This is a massive increase from the estimated population of 50,000 in 1983. Malnutrition is common, especially among children, and almost all of the population is dependent on subsistence agriculture.
African Great Lakes
The world's tenth-largest inland island, Idjwi, lies in Lake Kivu, as does the tiny island of Tshegera, which also lies within the boundaries of Virunga National Park; while settlements on its shore include Bukavu, Kabare, Kalehe, Sake and Goma in Congo and Gisenyi, Kibuye and Cyangugu in Rwanda.
Lake Kivu is one of three known exploding lakes, along with Cameroonian Lake Nyos and Lake Monoun, that experience violent lake overturns. The trigger for lake overturns in Lake Kivu's case is unknown but volcanic activity is suspected. The gaseous chemical composition of exploding lakes is unique to each lake; in Lake Kivu's case, methane and carbon dioxide due to lake water interaction with a volcano. The amount of methane is estimated to be 65 cubic kilometers). There is also an estimated 256 cubic kilometers of carbon dioxide. The methane is reported to be produced by microbial reduction of the volcanic CO2. The risk from a possible Lake Kivu overturn is catastrophic, dwarfing other documented lake overturns at Lakes Nyos and Monoun, because of the approximately two million people living in the lake basin.