There are many types of volcanic eruption, ranging from quiet extrusion of lava to very violent explosions. Hence volcanoes--the land forms created by such eruptions come in many shapes and sizes depending on the type of magma and it's gas content. Basaltic magma may form large shield volcanoes eg: Hawaii or small scoria cones such as in Auckland. Andesite eruptions form huge volcanic cones [strato-volcanoes] that may erupts for thousands of years eg: Mt Ruapehu. Rhyolite magma erupts in very different ways, it can ooze out of fissures forming steep-sided domes e.g. Mt Tarawera or it can be very explosive and results in the formation of giant calderas, basin-like depressions, which can then be occupied by lakes, fumeroles and hot springs e.g. Lake Rotorua. Coromandel Peninsula is an ancient volcanic region where erosion has occurred over millions of years leaving only skeletons. Pauanui Spit is comprised of 60 parallel dune ridges protecting Tairua Harbour. In the past 5000 years it has gradually advanced seaward at a rate of 6 to 40cm a year. The steep forested hills at the south end of Pauanui beach represent the western half of a massive ------- dome which formed 7 to 8 million years ago. Several parts of the dome cooled very slowly resulting in the spectacular columnar jointing seen around the coast south of Pauanui. The outer flanks consist mainly of lava flows and breccia deposits. With erosion and weathering several geological features have formed at GZ.
Parking is at the Southern beach end and then an easy seven minute walk to GZ. Here you must answer these questions and message them to the cache owners to get the thumbs up for logging the cache.
1] When was the Pauanui sandspit beginning to be formed?
2] What is the predominant type of igneous rock in this area?
3] What are four of the geological features displayed at GZ?
4] How were they formed?
All the answers can be found in a book called Vanishing Volcanoes. A guide to the landforms and rock formations of the Coromandel Peninsula. Written by Lloyd Homer and Phil Moore.