Much has been eroded but harder masses have remained and form striking landmarks such as St Paul's Dome. Other spectacular volcanic structures are best seen from the sea, around Pekapeka Bay just inside the Heads. This is one of the most prominent among the structures that share a common origin with St Paul's Dome. Taratara Rocks are located just west of SH 10 and the south-western end of Whangaroa Harbour. Auckland Little Barrier Island, Hauraki Gulf Little Barrier Island is an extinct andesitic volcano, which was active about 700,000 years ago.
Access is restricted because of the island's status as a wildlife sanctuary.
But Little Barrier's dark mass that can be seen from many places around the Gulf, and its inaccessible interior add a touch of mystery to the whole place. The Waitakere Ranges are a recently uplifted block of volcanic rocks. These rocks were either part of, or eroded from, the Waitakere Volcano, a large marine andesitic strato-volcano which was active between 22 and 15 million years ago. In the cliff at Maori Bay, Muriwai, two distinct types of features can be clearly observed. The first is an internationally significant outcrop of pillow-lavas.