Lake Rotoma is the fourth largest lake of the 11 lakes in the Rotorua Lakes district, or the Hot Lakes district as it was known in the early decades of the 20th century. The Rotorua lakes are located in New Zealand's North Island in the Bay of Plenty Region. Lake Rotoma is the easternmost in the chain of three lakes to the northeast of Lake Rotorua The other two are Lake Rotoiti and Lake Rotoehu. Rotoma is located halfway between the city of Rotorua and town of Whakatane.Lake Rotoma has a high water quality with visibility up to around 13 metres deep. The lake has a maximum depth of 83 metres in the northern part and 73.5 metres in the southern part.GeographyLake Rotoma was formed within the Rotoma caldera when lava flows from a large crater explosion blocked its outlet 9,500 years ago. The hills fringing the south and east of the lake are made up of Rhyolite from Haroharo and Tarawera, and this has meant that Lake Rotoma has no surface outlets. However, the presence of springs has suggested an underground discharge of lake waters. The water level of Rotoma reaches an excessive high or low level every 10–15 years. In times of extreme low levels, the sunken island "Motutara" in the lake may be exposed.