The region around the city of Rotorua, in New Zealand's North Island, contains several lakes which have a total area of about 250 square kilometres (97 square miles). The term Rotorua lakes is ambiguous as it has been used historically for a New Zealand administrative area. From biggest to smallest, these are Lake Rotorua (Second Lake), Lake Tarawera, Lake Rotoiti (Small Lake), Lake Rotomā (White Lake), Lake Okataina, Lake Rotoehu (Muddy Lake), Lake Rotomahana (Warm Lake), Lake Rerewhakaaitu, Lake Rotokākahi (Green Lake), Lake Okareka and Lake Tikitapu (Blue lake). There are also smaller lakes including: Lake Okaro, Lake Rotokawa (not to be confused with Lake Rotokawa near Taupō), Lake Rotokawau and Lake Rotongata (Mirror Lake).[1] Most of the lakes have formed due to volcanic activity and some have current geothermal activity. The region is part of the Taupō Volcanic Zone, the world's most active area of explosive silicic volcanic activity in geologically recent time.[2]