January 17, 2018 | David F. Coppedge

Hidden Volcano Comes to Light

It was the largest volcanic eruption of its kind in history. It happened five years ago. Did you hear about it? Probably not. Here’s why.

Under the sea, in 2012, a volcano erupted that set new records. Here’s what Science Advances (the open-access journal of the AAAS) says about it:

The 2012 submarine eruption of Havre volcano in the Kermadec arc, New Zealand, is the largest deep-ocean eruption in history and one of very few recorded submarine eruptions involving rhyolite magma. It was recognized from a gigantic 400-km2 pumice raft seen in satellite imagery, but the complexity of this event was concealed beneath the sea surface. Mapping, observations, and sampling by submersibles have provided an exceptionally high fidelity record of the seafloor products, which included lava sourced from 14 vents at water depths of 900 to 1220 m, and fragmental deposits including giant pumice clasts up to 9 m in diameter. Most (>75%) of the total erupted volume was partitioned into the pumice raft and transported far from the volcano. The geological record on submarine volcanic edifices in volcanic arcs does not faithfully archive eruption size or magma production.

Reconstructed images of the Havre volcano (Fig. 2 in the paper in Science Advances). See paper for caption.

Undersea volcanoes are hard to detect, but that’s where 70% of earth’s magma output takes place. This eruption, from an undersea volcano named Havre in the ocean north of New Zealand, is opening geologists’ eyes to things that are little understood:

Recent observations of explosive and effusive submarine eruptions in the Tonga and Marianas volcanic arcs have driven a surge in understanding deep, low-intensity, mafic end-member eruption styles. In contrast, the behavior of deep silicic eruptions in submarine settings is much less well known. Our understanding of deep silicic submarine eruptions is based largely on studying uplifted ancient successions, where details are limited by restricted exposures and missing context such as knowledge of timing and duration, source vents, and water depths. Direct insights are possible from modern seafloor deposits, but observational records of silicic submarine eruptions are rare, duration and timing information are not available, and there are no examples where the products of a large submarine silicic eruption have been mapped and characterized shortly after eruption.

All that began to change on July 19, 2012, when Havre erupted big time, sending lava out multiple vents for most of a day. The plume from the 4.5 kilometer wide circular caldera was first noticed by satellite. Follow-up observations with ships and autonomous underwater vehicles have mapped out the seabed around the volcano. A pumice raft 400 square kilometers in area was discovered some 6 km away from the volcano—the largest product of the eruption. At the caldera, they found complex post-eruption effects, like mass wasting, rough and smooth areas, and stacked pumice boulders ranging from 1 to 6 meters in size. The coarse cliffs probably occurred as a result of post-eruption collapse of crater walls. The effusion rate, they estimate, is comparable to silicic volcanoes on land, such as Mt. St. Helens.

Much about undersea volcanism is still poorly understood. They conclude,

At Havre, the satellite-based record of the pumice raft and the detailed submarine survey permit us to calculate mass partitioning of pumice clasts into proximal versus rafted and hence distal environments. Our volume estimates reveal that most of the erupted volume (>75%) was transported away from the volcanic edifice. This percentage is comparable to that of similar magnitude subaerial [‘under air’] fall deposits. However, unlike subaerial fall deposits where exponential and power law relationships between deposit thickness and distance can be used to calculate mass partitioning and total mass erupted, there are no models for marine dispersal that incorporate water depth, duration of particle buoyancy, ocean stratification, current speed and direction, or sea-surface wind shear, all of which are necessary for prediction of marine dispersal. There is no direct evidence on Havre of the eruption that produced the raft, the most voluminous product of the 2012 eruption. Consequently, for similar events, submarine eruption size cannot be reconstructed accurately from seafloor or uplifted deposits; this lost information is a source of uncertainty when assessing magma productivity in submarine volcanic arcs.

In short, even a well-observed recent undersea eruption cannot reveal much about the history of marine volcanic deposits.

Whenever a big event like this happens, you have to wonder how often it happens. Were we just lucky to observe this major eruption? How common are they over the assumed billions of years of evolutionary earth history? Just one eruption like this every thousand years would result in 4.5 million similar eruptions during the earth’s assumed 4.5 billion year age, or 45 million if once per century. One would expect this would leave a tremendous record both on land and in the sea.

Evolutionists can claim that most of this history is erased due to plate tectonics. That may be, but science is supposed to be about what you can observe, not what you have to assume happened to eliminate the evidence your theory requires. If a well-documented recent eruption like this leaves many unanswered questions and “lost information” and uncertainty, how much do geologists really know about earth history that is not open to observation?

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