Sunday, 11 January 2009

Mauna Loa just after sunset

The Big Island of Hawai`i is dominated by two massive volcanoes, Mauna Kea and Mauna Loa. The former is a dormant volcano whilst the latter is active although not right now. They're both around the same height (approximately 14,000 feet or around 4,200 metres or so) and are so massive that they bend the Earth's crust beneath them.

Both are shield volcanoes, that is the lava they tend to produce is generally fast running which results in a volcano that is large and high but not your typical disaster movie V-shape, in fact they resemble an upturned shield, hence the name. Volcanoes such as the infamous Vesuvius produce a lot of ash during an eruption and tend to form a much more obvious V-shape.

Mauna Loa does actually have some astronomical observatories on it, but nowhere near the summit, it would be too dangerous. On average it erupts every decade and if one wants to use that statistic, it's well overdue another eruption. On the other hand, Mauna Kea last erupted over 4,000 years ago, if memory serves, and is classified as "dormant". The powers that be have determined that it's safe to build observatories at the summit - I won't disagree with them, I work there and so far haven't had to run away from an eruption and lava flow.

The image above is of Mauna Loa taken from the summit of Mauna Kea just after sunset. It's still not right, but for the first time I actually got Hugin to produce this panorama with no glaringly obvious seams (trust me, they're still there).

No matter, the vog wrapping around the west side of the mountain looks really cool (that's the right hand side of the panorama) as does the snow at the summit. The dip at the summit is the crater which might give you an idea of the scale - it's about 3 miles wide (5-km).


Protege said...

So Tom, "dormant" means it is expired, dead, never to erupt again? Or does that mean that it is just "sleeping" and can suddenly awake with full power. If the last is the case, will there be any waring signs before it does? As I sure would be worried about that, if I was working so close to a volcano.;))

Tom said...

I'd have to look up the proper definition, but in the meantime "dormant" means it hasn't erupted for a long time but might erupt again.

An "extinct" volcano is one which won't erupt again. None of the volcanoes on the big Island are extinct although I think Kohala might be considered that way, it hasn't erupted for a long time now.

Don't worry, there'll be plenty of warning signs if Mauna Kea is about to erupt! I don't think we'll be taken by surprise, at least I hope not...