Moving Parliament: Wellington Earthquakes to Auckland Eruptions

Recently, NIWA scientists unveiled the discovery of a ‘new’ faultline in Wellington during investigations conducted by our sister project, It’s Our Fault. Prime Minister John Key was asked whether Parliament should be moved to a different city to try to mitigate the chaos that would certainly ensue if a large earthquake occurred under Wellington. Campbell Live jumped on the train shortly after, asking for the public’s opinion of a Parliament move to Auckland on Facebook and Twitter:

Protests of ‘but what about all the active volcanoes in Auckland?’ immediately erupted:

We’d be going from the frying pan and into the fire, is what many are thinking. But would we? That Auckland’s volcanoes could erupt again is one of the most common misconceptions I hear. Here’s what the evidence says: the Auckland Volcanic Field itself is dormant, but the individual volcanoes in it are extinct. This means that we expect eruptions to happen in Auckland in the future. It just won’t be at an existing volcano (with the exception of possibly Rangitoto (that sordid story here)).

For an existing Auckland volcano to erupt again, there has to be an established pathway from the magma source in the mantle to the volcano, and possibly a magma chamber, stewing away, underneath. We have absolutely no evidence that any magma chambers exist under any Auckland volcanoes.

Sketch of a magma reservoir and conduit beneath a volcano

Magma rising through the crust to the surface, pooling in a magma chamber before erupting. We have no evidence that magma is hanging around under any Auckland volcanoes. Sketch by B. Myers, image credit: USGS, http://volcanoes.usgs.gov/images/pglossary/magma.php.

We think that in volcanic fields such as Auckland’s, the magma pushing its way to the surface perhaps cools and ‘seals’ up the route that it took. This blocks future batches of magma from taking that same route, as later magma batches find it much easier to push through soft sediments than hard, cool lava.

In Auckland, there just doesn’t seem to be enough magma rising to keep the connection open to feed the same volcano over and over again. This results in a field of many small volcanoes instead of one single, large volcano.

So, the volcanoes in Auckland seem to be one-shot deals.

I am certainly not advocating a move, and an Auckland-based Parliament would be threatened by future eruptions in the field, but Auckland may be a bit safer from those 55 volcanoes than some think. So, does this change your opinion of a move?

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