Sunny Caves
Welcome to Hochstetter Pond. Known by the locals as "The Pond". This area was home to early European Settlers and the geological features have been noted on maps as far back as the 1860s. Named after Austrian geologist Ferdinand von Hochstetter, who surveyed the geology of Auckland in 1859.
Freshwater phytoplankton (tiny organisms) were abundant in the pond and their silica skeletons accumulated on the floor, forming a bright white sedimentary deposit called diatomite. This diatomite filled up the pond to the level of the present swamp.
At the posted coordinates, you are standing on the remains of a house's walls, steps, and foundation. This area the rear side of a wooden villa that stood here that was built by William Barron starting in 1877. Some 40-odd years after his death, The Donaldson family set up and then occupied this area, using the sediment built up in the wetland and selling it to breweries who used the diatomaceous earth for filtration. In the 1940s and 1950s the pond was drained (see the concrete walls) and the shallower diatomite deposits were quarried and sold locally. Continuing to sell the earth products, the family eventually opened up a nursery and marketed the earth as an abrasive cleaning product called Grotto Maid.
Although attempted were made over the years to buy the land to create a wilderness reserve, it wasn't until 2006 that the ownership properly passed to Auckland Council.
It is a small area and you aren't supposed to approach the wetland, but it is a nice area to bird watch or enjoy the sun!
Enjoy your time here!
Warning:
Do not approach the wetland.
Please be careful on the paths. They can be steep and slippery when wet.
Earthcache Logistics:
The area is easily reached by bike, by foot, or by public transit.
Parking can be found on the street, please pay attention to any postage signage.
This cache should only take you a few minutes, but if you have more time, go to the viewpoint at the northern end of the park.
You will need to visit the posted coordinated and answer a few questions.
This Earthcache should not be done at night, as you won't really be able to see to answer the questions.
This cache can be fun for all ages, but make sure you pay attention to kids running around on the hills.
There are a couple of information signs in the park, if you are interested they are worth the read!
Mostly, HAVE FUN!!!
---So, let's get to the GEOLOGY.---
Although there are several theories about what this Pond (and the nearby "Grotto") are, the leading theory is that these two areas were formed 67,000 years ago when the roof of a lava cave from the Maungakiekie / One Tree Hill volcano eruption collapsed.
This likely occurred while lava was still flowing through the cave, rafting away the thick roof material and leaving two, usually deep vertical-edged trenches. Later eruptions from neighboring volcanoes covered the area in volcanic ash, which is thought to have half-filled the trenches and blocked the drainage of the ponds, resulting in the pond/wetlands seen today.
There are several uneven horizons of scoriaceous ('bubbly' volcanic rock) material in the grotto's walls. This shows us that there have been at least three lava flows/flow pulses. Studies in the area have shown that in the vicinity of the pond, the lava is about 25 meters thick, suggesting that there is around 10 to 15 meters of lava below the surface of the pond.
On the northeast of the pond, there is a 3 meter thick later of bedded volcanic ash (tuff) which was deposited after an eruption from one of its younger neighbors, most probably from Rarotonga / Mount Smart which is 1.3 km away. There are rare angular basalt bombs (chucks of volcanic rock ejected during an eruption) that are up to 6cm in diameter that are unlikely to have reached this distance from other mountains nearby such as Three Kings.
Spread around the park is evidence that this area was a lava flow, exposed basalt can be found throughout the grounds. Under the plant life on the vertical walls, basalt can be spotted. Basalt is what remain after lava flows through an area and cools. The sheer basaltic walls and floor indicate this could have been a cave instead of just a normal lava flow. Basalt and scoria have been used to make the nearby walls. Their large size indicates it did not come from too far away.
How to log this Earthcache:
(Answered to be sent to my geocaching account, photos can be posted with the log.)
A) At the Posted Coordinates / Stage One, you will be standing on the remains of the old house foundation and stairs.
Q1) Please take a photo of yourself, your GPS, your caching name on a piece of paper, or even your shoe while overlooking the wetland below.
(Photo required for logging, so I know you visited the park).
(See example photo in gallery)
Update - 14 Feb. 2023: The photo is absoluetly REQUIRED to be attached to the log, no exceptions. Do not send the photo to the CO, post it in the log. This photo only need to be proof you visited. It can be as simple as your caching name on a piece of paper. Thank you!
Q2) Looking at the wetland, how high (deep) would you estimate the lava cave height to have been? (Compare the high points on the walls to wetland bottom - don't forget to add the lava from underneath the pond surface). (Note: I'm not asking about volume, length or width of the cave).
B) Posted coordinates or anywhere in the park.
Q3) What evidence do you see that would support Hochsetter's theory that this is a collapsed lava cave? Explain how it supports his theory.
(evidence can be a photo in a private geocaching message to me with an explanation message)
COPY / PASTE QUESTIONS :
For your convenience, you can copy / paste the questions to answer from here:
Required questions for logging -
Q1) Please take a photo of yourself, your GPS, your caching name on a piece or paper or even your shoe while overlooking the wetland below.
Q2) Looking at the wetland, how high (deep) would you estimate the lava cave height to have been? (Compare the high points on the walls to wetland bottom - don't forget to add the lava from underneath the pond surface). (Note: I'm not asking about volume, length or width of the cave).
Q3) What evidence do you see that would support Hochsetter's theory that this is a collapsed lava cave? Explain how it supports his theory.
Need help?
Are you confused on a question? On the optional math? Don't stress! I'm looking for answers that showed me you went to the site and tried.
If there are any problems I will contact you and I am happy to help further or add some information.
If you have any further questions, please feel free to send me a message, read the information boards or look at the following references.
Logging:
Feel free to log this Earthcache immediately.
However, after 10 days, any log that is not accompanied by a message with the answers and a photo will be unceremoniously deleted.
Update - 14 Feb. 2023: The photo is absoluetly REQUIRED to be attached to the log, no exceptions. Do not send the photo to the CO, post it in the log. This photo only need to be proof you visited. It can be as simple as your caching name on a piece of paper. Thank you!
References:
Maungakiekie-Tamaki Local Board & Auckland Council Interpretive Signage at location.
Hayward, B.W. 2019. Volcanoes of Auckland: A field guide. Auckland University Press: p.144-145.
Cameron;E.K.;Hayward;B.W.;Murdoch;G.;2008. A field guide to Auckland. Exploring the region's natural and historic heritage.;2nd ed. Godwit;Auckland. p. 231.;