Part of the Auckland volcanic field, it was created by a series of explosive eruptions. Although its age is unknown it could be one of the older volcanoes in Auckland like its neighbours Onepoto and Lake Pupuke. Originally a freshwater lake, it later became a tidal lagoon when the sea levels rose after the last ice age. Tank Farm is mostly in its natural state, though some parts of the tuff ring were quarried and its name stems from the petrochemicals storage tanks located here during World War II.