Background
Dunedin is situated atop the extinct shield volcano Rakiriri. The maori name derives from Rangiriri or Goat Island in Otago Harbour, which is more or less the centre of the volcano. The name literally means "angry sky" (from Wild Dunedin - Neville Peat and Brian Patrick). The volcano spanned the area from Waitati to Brighton and Taiaroa Head to Whare Flat. The walk to GZ (don't go any further than the end of the flat path) takes in volcanic features such as basalt pillows, columnar basalt and ash layers. These are remainders of what was once a very active area.
More Detail:
Basaltic pillow lava occurs where molten rock is extruded under the sea forming "pillow-like" balls.
Oamaru pillow lava
Source: www.teara.govt.nz
Columnar basalt forms when molten rock cools slowly underground (ie intrusive rather than extrusive). The rock fractures as it cools forming distinctive often hexagonal columns. Dunedin's organ pipes and the Giant's Causeway in Ireland are examples.
The Organ Pipes
Source: www.sciencelearn.org.nz
Ash layers form as successive layers of ash, cinders, tephra etc are ejected from the volcano. As different material may be ejected over time layers of differing composition can build up or there may only be a single distinctive layer.
Please be mindful of children. The area at the end of the walk is unfenced and has a shear drop away to rocks and water.
Logging Requirements
0. Preface any email with GC3AMWR Rakiriri Remainders in the subject line and title and clearly note the question number and answer. Do not wait for a confirmation email to log but be prepared to be asked for additional information if your answers are slim.
1. Your task is to find one of the following along the walk to GZ: basalt pillows, columnar basalt or ash layers. You must provide detailed evidence that you have found the structure either by giving a comprehensive description (including location) or a photo (post publishing date) of the structure (with you or your GPSr in the picture). Email answer or photo to gcstegan"at"gmail.com
2012 Stegan’s EarthCache Masters Programme
It is not very feasible for many New Zealanders to get past the Bronze level on the earthcache.org programme becase you need three states for Silver which means leaving the country! So, as in 2010 I've decided to run a little sideshow on my new EarthCaches this year... with the following points system:
5 points: First to find
3 points: 2nd to find
1 point: Logging a find
1-5 points: Special bonus questions.
At the end of 2012, I’ll issue certificates for 1st, 2nd and 3rd.
Updated information and Leaderboard at: Stegan’s EarthCache Programme
Free counters