Lake Pupuke is the only lake of its type in the Auckland region. It is a maar crater that was formed about 140,000 years ago by a phreatomagmatic volcanic eruption (an explosion caused by groundwater coming into contact with magma). The lake is actually the result of two craters; anomalous magnetic readings near the entrance to the northeast arm suggest it is a small subsidiary explosion crater.
While other maars exist in the Auckland volcanic field this is the only one that remains as a lake and not buried by other eruptions, or breached by erosion and opened up to the sea. It however at its closest point is only 200m from the Hauraki Gulf.
The eruption of Pupuke resulted in the largest, most complex explosion crater on the North Shore and covered much of the Takapuna and Milford in volcanic material area.
Required Observation
To log this earthcache you will need to go to the published coordinates on the causeway between the Quarry Lake lagoon and Lake Pupuke. On the Lake Pupuke side you will see rocks lining the edge of the lake. In your own words describe the texture, shape, and colour of these rocks.
Additional (Optional) Task
Take a photo of yourself and/or your GPSr looking across to the opposite side of Lake Pupuke. Upload your photo with your log.
Logging
You can log this earthcache after you have emailed your observations to the cache owner. There is no need to wait for permission. Do not include your observations in your log on this page. Please include your email address if you would like a reply to your answers. Any logs that do not provide the above observations or blatantly incorrect observations, will be deleted.
(Sources: Lake Pupuke (Wikipedia), Maar (Wikipedia), Lake Pupuke Inspection Report No. KC71)