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Pencarrow Lakes (Wellington) EarthCache

Hidden : 10/29/2009
Difficulty:
2 out of 5
Terrain:
3.5 out of 5

Size: Size:   other (other)

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Geocache Description:

An EarthCache featuring the geological effect of earthquakes known as Raised Beach Ridges. These ridges are significant to the Wellington area as they give insights to the formation of Wellington Harbour.

You can walk or cycle to the cache. The terrain is flat on a well formed gravel road. It is some 8km to the cache so cycling is recommended. Park at Burdans Gate at the end of the Eastbourne coastal road. Whilst open to public access, this is a farm so please note due to Lambing, dogs are NOT ALLOWED during August, September and October.

The cache is located within the Wellington Eastern Regional Park, however dogs are allowed at other times but strictly on a lead.

At the GZ you will find a sign board. You will be required to gain some information and supply answers. There are other caches along the way so check the web site first.

This beach ridge was raised by earthquake uplifts prior to 1855. It is one of the best examples nationally of a raised beach ridge. It is also very important within the Wellington area, both ecologically and scientifically for the insights it offers into the formation of the Wellington Harbour and environs. Other examples of raised beach ridges in the Wellington area have in many cases been destroyed or concealed by quarrying, houses or roads. The profile of this ridge is constantly changing as it is affected by storms, wind, wave action and build up of sediment.



A former valley drowned by the sea now forms a fresh water lake behind the beach ridge. This is called Lake Kohangapiripiri, and occupies a valley which once was drowned as the sea rose at a greater rate than the land. The other lake in this park, Lake Kohangatera, was formed in the same way. The valleys became narrow inlets of the sea. The inlets were eventually cut off from the sea by the formation of spits about 2000 years ago. Later, continuous gravel bars were formed – which were widened by successive earthquake related uplifts during the last 1000 years. Lake Kohangapiripiri and Lake Kohangatera are now freshwater lakes draining to the sea through the raised beach gravel bars in front of them.



Lake Geology - Lake Kohangatera has about 17 ha of open water with a maximum depth of 2 metres and is described as mesotrophic (having moderate levels of nutrients). The lake has a soft organic base and the strong winds common to the area are likely to stir up bottom sediments and reduce water clarity. Sediments below the base are a dark grey, clayey mud with some sand.

Lake Kohangapiripiri has about 13 ha of open water, 1-2 metres deep, and is described as borderline oligotrophic/mesotrophic (having low to moderate levels of nutrients). A firm sandy base overlies brownish black mud. Changes to the outlet channel since the 1950s suggest that breaching had not occurred for ten years or more prior to 1995, however, it did breach in 2005 and 2006.

Go to the sign board and you may find the answer to some of the required questions here. Once you complete the following EarthCache requirements you can post your find without delay, as per the EarthCache guidelines. You will also need to verify your find by sending us a message with your answers to these questions and we will answer in due course:

1. Use the text "Pencarrow Lakes - GC20DQK" in your email.
2. What nests here between August & February?
3. What is the approximate depth of the lakes?
4.What is the elevation here?
5. (Optional) Take a photo of you and your GPS with the harbour entrance in the background. Merit will be given to photos featuring shipping.

Please note: Please DO NOT post answers with your log. Just post your photo. Please wait for our reply before logging your find.

FTF honours go to boxhill

Additional Hints (No hints available.)