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Ahuriri Lagoon (Hawkes Bay)

A cache by J 'N' K Send Message to Owner Message this owner
Hidden : 11/10/2009
Difficulty:
2 out of 5
Terrain:
3 out of 5

Size: Size: other (other)

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Geocache Description:

An EarthCache featuring the Ahuriri Estuary, a remnant of the Ahuriri Lagoon or Napier Inner Harbour. The cache requires a walk up and around Rorookuri Hill which was once an island in the middle of the lagoon. Parking is available at S 39° 25.922 E 176° 51.66.

The site has important spiritual and historical significance for Maori so please respect this very special place. You can take either the Summit or the Circular track but it is quickest to take the Summit track initially ( check out the views! ) then follow the Circular track to complete the requirements of the cache. Allow an hour to complete the cache. At certain times of the year thistles can be a problem so long trousers are recommended.

The tracks are closed during July, August and September for Lambing.

Ahuriri Lagoon was dramatically reduced in size in 1931 when the Napier earthquake lifted the bed of the lagoon between 1.5 and 3.4 metres, exposing approximately 1300 hectares of the bed of the lagoon and a further 1700 have since been reclaimed. This area is now used for farming and the regional airport.

BACKGROUND

The earthquake occurred at 10:47 am on Tuesday February 3, 1931, killing 256 and devastating the Hawke's Bay region. Centred 15 km north of Napier, it lasted for two and a half minutes and measured about 7.8 on the Richter scale. There were 525 aftershocks recorded in the following two weeks. The main shock could be felt in much of the lower half of the North Island. Nearly all buildings in the central areas of Napier and Hastings were levelled (The Dominion noted that "Napier as a town has been wiped off the map") and the death toll included 161 people in Napier, 93 in Hastings, and two in Wairoa. Thousands more were injured, with over 400 hospitalised. The local landscape changed dramatically, with the coastal areas around Napier being lifted by around two metres. Some 40 km² of sea-bed became dry land, where the airport, housing and industrial property developments now exist.

HISTORY

The combined estuary and lagoon area of the Waiohinganga and Tutaekuri Rivers (known as Ko te Whanganui o roto) was a valuable food source for local Maori of the Hawke's Bay Region. The Ahuriri area is important to Maori for cultural and spiritual reasons including the events that occurred on Te Pakake Island. Te Pakake was a low, sandy island located just inside the Ahuriri Heads next to Te Koau (Gough Island).

Te Pakake Island has historical importance for its function as a fishing village for the local tribes including Ngati Parau, Ngati Hinepare and Ngati Mahu, as a fighting pa (place), as a place of communal sanctuary during times of war, and as a burial ground. Perhaps what it is most well-known for is for the Battle of Te Pakake.

GEOLOGY

Scientists now know that this earthquake occurred on a buried, or blind thrust, fault. These are earthquake-generating faults that do not extend up to the earth's surface and they occur in most of the tectonic plate boundary zones of the world. As well as being hidden, blind thrust faults also pack a big punch when they rupture. Because the two sides of a thrust fault are being compressed like a vice, it takes a lot of energy to rip them apart.

The explosive release of this energy produces high intensity ground-shaking, and scientists consider them to be a particularly lethal type of geological fault because they show little or no evidence at the surface and, even when detected, are difficult to study.

Such faults, being invisible at the surface, have not been mapped by standard surface geological mapping. Sometimes they are discovered as a by-product of oil exploration seismology; in other cases their existence is not suspected. These blind thrust faults are predominant on the North Island's east coast between Wairarapa and East Cape.

Although such earthquakes are not amongst the most energetic, they are sometimes the most destructive, as conditions combine to form an urban earthquake which greatly affects urban seismic risk. It is said that blind thrust earthquakes contribute more to urban seismic risk than the 'big ones' of magnitude 8 or more. This was definitely the case in the Napier earthquake.

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 "Ahuriri Lagoon - GC20WX2" in your email.
2. The parking co-ords (S 39° 25.922 E 176° 51.66) will take you to a sign board. What popular pastime was Rorookuri Island used for?
3. (Optional) The sign board shows two photos. One has a woman standing in the foreground of a photo taken from the published co-ords. You need to duplicate this photo on the day of your visit replacing the woman with yourself. Please post it with your log.
4. Locate the old pa site of Otiere pa, how was this pa defended?
5.What can be clearly seen on the ground at S 39 25.988 E 176 51.094 that reminds us what was here prior to the 1931 earthquake?

NOTE: Please DO NOT post answers with your log. Just post your photo.

FTF honours go to tndtnd.

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