Before 1883, the area of Krakatau islands consisted of 3 volcanoes and 2 small islands. The volcanoes are Rakata, Danan and Perbuwatan while the islands are Sertung and Panjang Island. It has horrifyingly erupted in 1883 and the sound of the eruption can be heard from Australia and Rodigues Island. Its explosive power estimatedly reached 30.000 times of Hiroshima and Nagasaki Atomic Bomb Explosion. It has destroyed the two volcanoes and left Rakata volcano standing alone with a cut-off cone that turned into a cliff. The eruption itself was one of the first global news events after telegraph lines had connected different continents.
After less than a half century stable situation, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Child of Krakatau has been the site of frequent eruptions since 1927. Periodic eruptions have continued since, with recent eruptions in 2009, 2010, 2011, 2012 and March 2014. According to local ranger, there are always significant signs when the mountain is about to erupt. They are always carefully monitored by the responsible institutions to make it save for the tourist to visit. However, frequent check will always be the best way to guarantee safety.
In 1991, UNESCO acknowledged both Ujung Kulon National Park and the Krakatau Islands Nature Reserve as an integrated UNESCO Natural World Heritage site. Now, the islands have become a major case study of island biogeography and population study especially related to ecosystem built upon virtually cleaned ground environment.