More plaudits for Tiritiri Matangi

Date posted: 15-Jul-2019

Recognition of the wonderful experience visitors have when visiting the Island h..

Results of the 2019 Photo Competition

Date posted: 15-Jul-2019

The results of this year's competition have now been decided. Click here (/2019-photo-co..

Lighthouse Open Day

Date posted: 30-Apr-2019

Our historic lighthouse, signal station and diaphonic foghorn will all be on dis..

We need a new Treasurer

Date posted: 08-Apr-2019

The Supporters need a new treasurer to take over in September when Kevin Vaughan..

2019 Concert

Date posted: 05-Feb-2019

OrigiNZ, the tartan taonga are returning for the 2019 concert. Click..

Tiri's three unique foghorns

Date posted: 01-Feb-2019

Our next social event will take place on Monday 18th March when Carl Hayson and ..

Young Conservation Superstars win awards!

Date posted: 27-Jan-2019

Gabriel Barbosa and teacher Kate Asher, a team leader who co..

Entries for the 2019 photo competition

Date posted: 19-Jan-2019

We are now taking entries for the 2019 photographic competition. You can enter u..

Hihi volunteer needed

Date posted: 18-Oct-2018

Would you like to volunteer with the Island's hihi team and learn from them how ..

2019 Calendars now available

Date posted: 05-Sep-2018

The new 2019 calendars are now available and this year's is better than ever! Th..

Geology


Travelling from Auckland or Whangaparaoa to Tiritiri Matangi, the typical 'whitish' cliffs of the Auckland area shine out in the sun. These are the familiar 'Waitemata Group' rocks. They are made up of mainly alternating layers of sandstone and mudstone, interspersed irregularly with thick beds of volcanic debris flows. The Waitematas were laid down in a submarine basin between 22 and 18 million years ago. During that time, volcanic activity began to the west of Auckland, the only remnants being the Waitakere hills. The Waitemata basin was then uplifting about 17 to 15 million years ago and erosion began.
 
In contrast to the Waitemata Group rocks, the cliffs on Tiritiri Matangi are darker and less clearly stratified. These rocks are much older, part of what is called the 'Greywacke Basement' of New Zealand. These rocks are also mainly mudstones and sandstones which were laid down on the deep ocean floor between 270 and 150 million years ago. They were compressed, fractured and folded in higher temperatures and pressures as they were buried beneath many kilometres of rock. Subsequently, about 100 million years ago, during the early cretaceous period, these rocks were uplifted and began eroding. They later formed part of the basement of what was to become the New Zealand continent. The greywackes, of which Tiritiri Matangi is a part, are known as the 'Waipapa Terrain'.

Greywackes underlie the whole of Auckland. Faulting and uplift to the east of the city have exposed these on Tiritiri Matangi, as well as on Motutapu, Waiheke, and in the Hunua Ranges which are uplifted Waipapa greywacke. Most of the Waitematas which overlay Tiritiri Matangi have been eroded off since the basin was uplifted. They are now only seen on the north east tip, unnoticeable to most visitors.  

Helen Holzer

Photograoh by Kay Milton ©