Greetings, my fellow port swillers!

Ol’ Robbo has noticed that the current eruption of the Kilauea Volcano seems no longer to be grabbing headlines for the moment.  I gather that, having done some damage (and what idiot builds next to an active volcano?), the lava has established its primary path to the sea and is busily heading that way without bothering anybody else.

When we were all gathered together the other day, somebody in the Port Swiller Manor household referred to this eruption in the context of the Pacific Rim of Fire.  Ol’ Robbo couldn’t allow this.

“Not so,” says I. “The Hawaiian Islands sit over a volcanic hotspot – a stationary thin point in the Earth’s lower crust – right smack dab in the middle of the Pacific Plate.  This, in fact, isn’t a tectonic thing, but a different phenomenon altogether.”

At which point the family’s collective “toxic nerd alert” alarum seems to have gone off, as suddenly Ol’ Robbo found himself talking solely to one of the cats, who was asleep anyway.

Hmpph!

Nonetheless, the geography of Hawaii does, in fact, have a tangential connection with plate tectonics, in that it neatly maps out the drift of the Pacific Plate over this particular hotspot.  As you can see from just looking at an ordinary map, the chain runs from southeast to northwest, the islands getting progressively smaller as you go along.  This is because the Plate itself is drifting northwest:  As long as some bit of it is over the hotspot, that bit is subject to volcanic island formation and growth.  Once the islands drift away from the hotspot, they start to erode.  Eventually, the Big Island, which is now the active one, particularly on its southeast side, will slide away from the hotspot and start to crumble and shrink as well, while yet another one eventually rises up southeast of it.

Pretty neat, eh?

And want to hear something even neater?  Go look at Google-Earth on “satellite view” setting:  Not only will you see the Hawaiian chain continue trailing away to the northwest under water, eventually you’ll see it hook sharply north and trail all the way up nearly to far eastern Russia.  That north-south section – the remnant of long-ago passage over the very same hotspot – is known as the Emperor Seamounts, and shows that the Pacific Plate at one point was drifting due north before taking a turn northwest.

And don’t just take my word for this: John McPhee writes at some length about it (and provides an illustrative map) in his Annals of the Former World, which Ol’ Robbo plugs here from time to time (and, I guess, is plugging again), and which I cannot recommend too enthusiastically.  I don’t pretend to understand it at more than a surface level, but the makings of the Earth – from plate tectonics to continental drift, volcanic hotspots to glacial gougings, erosion to geologically-driven shifts in weather patterns – never ceases to amaze and delight me.