Mahia Tombolo EarthCache
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Mahia Island and the Mahia Tombolo lie at the north-eastern end of Hawke's Bay, on the east coast of the North Island. The peninsula, 13½ miles long and 7 miles wide, rises to its highest point at Te Kapu, 1,302 ft.
A tombolo (from Latin tumulus - mound) is an Italian name-accent on the tom- or sometimes ayre (Old Norse Eyrr - gravel beach) is a deposition landform in which an island is attached to the mainland by a narrow piece of land such as a spit or bar. A tombolo is formed when the wave refraction patterns from two landmasses cause sand and other materials to be deposited between them, eventually forming a bridge between the two. Once attached the island is then known as a tied island. They usually form because the island causes wave refraction, depositing sand and shingle moved by longshore drift in each direction around the island where the waves meet. Eustatic sea level rise may also contribute to accretion as material is pushed up with rising sea levels.
The island now know as Mahia Peninsula was created by displacement of the upper plate of the Hikurangi subduction zone, which results from the convergence between the Pacific and Australian tectonic plates. The Pacific Plate is being subducted under the Australian plate. This area is prone to earthquakes, with a consequential risk of tsunami. By the end of the Pilocene, the Maia block of seafloor had probably been uplifted sufficiently to be an island. Uplift of the coastal landscape often would probably have been accompanied by an earthquake of greater than 7.5 magnitude.
Mahia "Peninsula" was then formed as sediment filled in between the land masses, forming a tombolo, connecting the island to the North Island. Technically speaking, it should be referred to as Mahia Island.
And that might get you thinking that an island connected to the mainland isn't truly an island, that peninsula is actually the right name for this. And indeed, the French have a word, presqu'île, almost-island, for that. There's a tombolo involved at Presqu'Île Provincial Park on Lake Ontario, Canada, for instance. But a peninsula is usually bedrock of the same sort as the land around it, whereas a tombolo is a pile of sediment.
Tombolos are temporary things, mostly because the islands don't tend to last that long. The sea makes quick work of them, geologically speaking, wearing them down to the waterline in a few thousand years or so. Then the tombolo loses its protection and disappears.
The island is tied to the mainland near Opoutama.
The area is deservedly a popular seaside resort. The chief activity of the area is sheep farming with some beef cattle. Maori legend states that Whatonga, who came to New Zealand in search of his grandfather, Toi, settled at Mahia. Portland Island, the site of a lighthouse, is a small island off the southern tip of Mahia. The name Mahia means "indistinct sound". According to another Maori legend, Mahia Peninsula is Te matau a Maui - the fish-hook of Maui.
To claim this Earthcache you must do the following:
1. Send an email with the answer to the following questions:
what event most likely created Mahia Island in the first place? Briefly describe the features of the beach that is at the listed coordinates. Is this beach part of the island or the tie to the island? and what features about it can lead you to this conclusion?
2. Go to the listed coordinates which is one of the nicer beaches (in my opinion) on the island and post a picture of yourself and you GPSr unit.
Additional Hints
(No hints available.)