Auckland’s Lava Caves

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Over the past few years, we have undertaken far reaching exploration efforts of the Auckland Volcanic Field, uncovering new and undocumented lava caves. This initiative employs rigorous field research and exploration, complemented with unique discovery methodologies and leading edge technology.

Our recent efforts have yielded particularly noteworthy discoveries, including many significant lava caves documented to date. Among the most fascinating features are intricate mineral formations including delicate crystals, bizarre coralloid speleothems and unusual crusts that adorn the cave walls. Furthermore, we have observed the presence of peculiar bacterial films, adding another layer of complexity to these unique ecosystems.

This page provides extensive information on Auckland’s lava caves, including their geological formation, unique morphology and features. Additionally, you can find comprehensive documentation of our recent discoveries, including surveys, detailed photographic records, and scientific analyses.

Some of the remarkable lava caves we have discovered – Mira and Pollux Caves

 

Overview

The Auckland Volcanic Field (AVF), a monogenetic volcanic field encompassing the Auckland region, is home to a remarkable geological feature: a vast network of lava caves. These caves exhibit an incredible diversity in their morphology. Some are simple tubes, while others form intricate networks with multiple levels and chambers, extending for hundreds of meters. They are wonderful time capsules that preserve clues about past eruptions, lava flow patterns, and the evolution of the landscape over the last 200,000 years.

Formation

As the molten lava flows downhill from a volcanic vent, the exposed surface begins to cool and solidify due to interaction with the cooler ambient air. This cooling process leads to the formation of a solid crust on the top and sides of the lava flow, while the insulated interior remains molten and continues to flow. Over time, the continuous flow of lava within the hardened shell gradually drains out, leaving behind a hollow, tunnel-like structure. The solidified outer crust acts as the roof and walls of the cave, preserving the shape of the original lava channel. Variations in the lava flow rate, cooling rate, and terrain can result in diverse cave morphologies, including sinuous tubes, multiple levels, and even dome-shaped chambers formed by gas bubbles trapped within the lava.

⇨ More information on the formation of Auckland’s Lava Caves

Cave Types

The primary lava type found in the AVF is basalt, a low-viscosity lava that flows readily and cools relatively quickly. The fluid nature of basaltic lava often leads to the formation of long, sinuous lava tubes. These tubes typically exhibit smooth, ropy surfaces known as pahoehoe, formed by the wrinkling and folding of the cooling lava crust. While individual lava tubes are common in the AVF, some caves form complex systems with multiple levels, interconnected passages, and even chambers. These systems are often created by multiple lava flows that occur over time, with each new flow adding to or modifying the existing cave structure.

 

⇨ More information on the types of Lava Caves in Auckland

Cave Features

Lava caves exhibit a fascinating array of geological features. They often possess smooth and undulating walls, shaped by the flow of molten lava during their formation. The interiors can include intricate patterns and textures, such as lava shelves, terraces, and benches, formed as the lava gradually receded or solidified at different rates. Lava stalactites and stalagmites may also form from dripping lava or mineral deposits left behind by water seepage. Floors can vary from rough and rocky to smooth and glassy, depending on the lava’s composition and flow dynamics. Some caves may feature skylights or collapse pits where the roof has caved in, allowing natural light to filter into the underground passages. Additionally, secondary minerals like gypsum, calcite, and various silicates may adorn the cave walls.

 

More information on features found in Auckland’s Lava Caves

Cave Mineral & Film Deposits

Lava caves, while primarily composed of solidified lava, exhibit a remarkable diversity of secondary mineral formations. These deposits often form after the initial cave formation, as mineral-rich water seeps through the porous lava rock, leaving behind a variety of mineral precipitates. Common minerals found in lava caves include gypsum, which can form delicate, translucent crystals or intricate flower-like formations; calcite, which can create a range of speleothems such as stalactites, stalagmites, and flowstone; and various types of opal, which can exhibit a wide array of colors and patterns. Additionally, bacterial biofilms, complex communities of microorganisms, frequently colonize the cave surfaces. These biofilms often appear as white or colorful coatings.

 

⇨ More information on mineral and film deposits in Auckland’s Lava Caves

Cave Discoveries

We have discovered approximately 30 previously undocumented lava caves within the AVF. Several of these are considered to be among the most significant AVF lava caves recorded to date. These significant caves have undergone comprehensive surveys and documentation, with the resulting data incorporated into the New Zealand Speleological Society Cave Atlas Database. Other caves were determined to be of lesser significance and therefore have not been surveyed, nor listed below.

⇨ Mira Cave
⇨ Cygnus X-1 Cave
⇨ Capella Cave
⇨ Pollux Cave
⇨ Castor Cave
⇨ Son of Gemini Cave
⇨ Weeping Well Cave
⇨ Alcyone Cave
⇨ Electra Cave
⇨ Deep Shaft Cave

Conservation

Due to their cultural, historical, and geological significance, many lava caves in Auckland are protected under the Auckland Unitary Plan. The plan designates many lava caves as Outstanding Natural Features, affording them legal protection. This ensures that any development or activity affecting these caves requires thorough assessment and consideration of their ecological and cultural values.

Important Disclaimer

Lava cave exploration can pose a serious risk to personal safety due to unstable terrain, potential for rockfall, and lack of oxygen. Cave entrances are often located on private land and require land owner permission before entering. These unique ecosystems are also home to delicate mineral formations as well as flora and fauna, which are highly sensitive to disturbance. Additionally, many lava caves hold deep cultural and spiritual significance for Māori, who consider them sacred sites. Respecting these values and preserving the caves’ pristine condition is crucial for both scientific and cultural reasons.