Geology
Other similar craters in the Auckland Volcanic Field were either buried by later eruptions, or breached by erosion as rainwater collected and overflowed the edge of the crater. Lake Pupuke remains a lake because, unlike the other vents, its eruptions produced substantial lava flows; water can thus escape through cracks in the lava reaching under the crater wall, creating a series of freshwater springs along the beaches between Takapuna and Milford. The lava flow at the end of Takapuna Beach enveloped a kauri forest, producing an internationally significant collection of tree moulds, which has been called "New Zealand’s only example of a fossil forest preserved in a lava flow" and which "ranks among the best examples in the world." Some moulds have escaped burial by the boat ramp and car park built on top of the lava, and can be viewed at low tide.
Read more about this topic: Lake Pupuke