The Krakatau volcano is indeed a Caldera. It is 813 meters high and is located at 6.1 Degrees South and 105.423 Degrees East. Krakatau is a Stratovolocano and this is considered to be one of the most dangerous types of volcanoes. The low viscosity and silica in the magma indicates that the lava flow will be extensive and destructive.
The word “caldera” is from Spanish origin and means cooking pot. This situation occurs when the Stratovolocano erupts and so much material is expelled that the surface cone can no longer support the weight of the crust. It collapses in on itself and creates a pot like effect. The eruption of this type of volcano can cause a lot of destruction, shoot a great deal of ash into the atmosphere and affect temperatures around the world, over a period of time. The last major eruption of Krakatau was in 1883.