Sunday, May 11, 2014

New clarity on mysterious 1956 eruption in Kauai channel.

You’d think we would have Hawai`i’s volcanic geology well understood, but new mysteries pop up with regularity.

Like the report this week that O`ahu has a third volcano, besides the Ko`olaus and the Wai`anaes. 

They’re calling it Ka`ena, and it extends most of the way to Kaua`i. Now underwater, but once above the surface and connected to the rest of O`ahu.

(Image: This chart of the Hawaiian Islands shows the extended shallows to the west of O`ahu, which have now been identified as a separate volcano, Ka`ena, rather than a rift of the Wai`anae volcano. You can also see the spur to the southwest of Moloka`i, another volcano that forms Penguin Bank. Credit: USGS.)

O`ahu’s ancient shape is a lot, it turns out, like the configuration of Molokai, which has, from east to west, the volcano peaked by Kamakou, and the one at Maunaloa, and then the submerged volcano that forms Penguin Bank.

On the subject of the Ka`ena volcano, I refer you to Jim Borg’s excellent Honolulu Star-Advertiser piece on the Ka`ena volcano. If you're interested in the more technical view, here is an abstract of the original paper, written by a team led by John M. Sinton in the Bulletin of the Geological Society of America. 

Rather than review that information, I’ll make reference to a seemingly related nearly 60-year-old mystery, an apparent volcanic eruption in the Ka`ie`ie Channel, between Kaua`i and O`ahu.

It was May 23, 1956, a military flight over the channel spotted yellow water with debris on the surface and a distinct smell of sulfur in the air. Dead whales were reported in the area. Within days, pumice was reported washing ashore on O`ahu. 

There was lots of speculation at the time, some of which dismissed the reports. If there were an active volcanic vent between Kaua`i and O`ahu, we’d certainly know about it, after all.

Then, in 1991, a photographic survey of the ocean floor in the channel found fresh lava. The Associated Press report on that is here

Frisbee Campbell, vice president of the mapping firm Seafloor Surveys International, was quoted as saying, ''We found what looked like a very young lava flow. It could have been created yesterday or 100 years ago or 1,000 years ago, but it looks fresh, like you were looking at an area of the Big Island with a lava flow on it.''

Tom Wright, the respected long-time scientist in charge at Hawaiian Volcano Observatory, said that was consistent with the 1956 eruption.

Sinton’s new Ka`ena volcano report said it could not confirm a 1956 eruption from its own studies.
His paper suggested that the pumice that was found on O`ahu beaches was unlikely to have been from any late eruption activity on Ka`ena. Most references suggest pumice is formed during aerial eruptions, and it seems odd that pumice could form under the extreme pressure of an eruption a couple of thousand feet underwater. 

That said, the evidence of a mid-1900s volcanic incident in the Ka`ie`iewaho would seem compelling: yellow-brown water, dead marine life, the smell of sulfur, evidence of fresh lava on the channel floor, and now, news that there’s a big old volcano there.

 Ka`ena is reported from rock studies to be some 3.5 million years old, and Sinton's team said it once reached 3,000 feet above sea level. 

Interisland navigators have long known there's something odd going on underwater between Kaua`i and O`ahu, since the sea is very different on the O`ahu side of the channel than on the deeper Kaua`i side. It's one reason that the Ka`ie`ie channel has three distinct names: Ka`ie`ie Waho, Ka`ie`ie Waena and Ka`ie`ie Loko.

I'm guessing as to the boundaries identified by these ancient names, but I have paddled and sailed this channel, and the names make sense if understood this way:

If you have sailed on a trade wind day from Wai`anae to Nawiliwili, you will have known the calm, protected waters in the lee of O`ahu, the Ka`ie`ie Loko. 

And the steep, crashing waves over the shallower waters of what is know known as the Ka`ena volcano, the Ka`ie`ie Waena. 

And finally, the longer surfing swells as water deepens andKaua`i comes into sight, the Ka`ie`ie Waho.

Which raises the question of whether the new volcano ought to be named after a spot on the Wai`anae range, Ka`ena. Or should it have the Hawaiian name for the waters it creates: Ka`ie`ie Waena?

© Jan TenBruggencate 2014

1 comment:

Anonymous said...

Great Article!