Monday, October 20, 2014

Big tsunami: Just 500 years ago, a 9.25 magnitude Aleutian quake blasted Hawaiian shores

A stunningly large Aleutian-sourced tsunami hit the Hawaiian Islands 4-500 years ago, requiring a much more aggressive assessment of potential shoreline damage from future waves.

Much of the preliminary evidence for the big wave comes from the Makauwahi Sinkhole on south Kaua`i, but scientists expect to find more evidence once they start looking for it on other islands.

(Image: Researchers simulated earthquakes with magnitudes between 9.0 and 9, and found that the unique geometry of the eastern Aleutians would direct the largest post-earthquake tsunami energy directly toward the Hawaiian Islands. The red circles are centered on Kaua‘i and encircle the Big Island. Credit: Rhett Butler)

And what that means is that it could happen again.

A report on the wave was published this month in the journal Geophysical Research Letters. The article, “Paleotsunami evidence on Kaua‘i and numerical modeling of a great Aleutian tsunami,” was written by Rhett Butler of the Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, David Burney of the National Tropical Botanical Garden and David Walsh of the Pacific Tsunami Warning Center.

 Burney’s investigations of the sinkhole revealed a huge layered collection of marine debris that he determined could only have come from a tsunami, ripping up coral and rock from the ocean floor and depositing it over a limestone shelf into the sinkhole. 

The wave came 300 feet inland and rose more than 20 feet to dump debris into the sinkhole.

It was the massive 2011 Tohoku quake in Japan, with a magnitude of 9.0, that raised the awareness of researchers that such events were possible. They now assume at a quake that large may occur from the Aleutians every 1,000 years or so.

To account for the Makauwahi dune debris layer, they figure the quake would have needed to be even bigger than Tohoku.

“Using high-resolution bathymetry and topography we model tsunami inundation of the sinkhole caused by an earthquake with a moment magnitude of Mw ~9.25 located in the eastern Aleutians. 

“A preponderance of evidence indicates that a giant earthquake in the eastern Aleutian Islands circa 1425–1665 A.D… created the paleotsunami deposit in Kaua‘i. A tsunami deposit in the Aleutians dated circa 1530–1660 A.D. is consistent with this eastern Aleutian source region,” said the paper.

And why is this kind of study important? The authors write:

“The focus of tsunami energy from the Aleutians directed toward the State of Hawaii, and the short 4.5 (hour) tsunami propagation time, underscores the importance of tsunami readiness for Aleutian events. Hawaii State Civil Defense must make evacuation decisions 3 (hours) prior to tsunami arrival.”

© Jan TenBruggencate 2014

Sunday, October 5, 2014

Defining farming: it means what I choose it to mean

There’s a lot of discussion on Kaua`i and elsewhere about what constitutes agriculture, and whether it’s only farming if you’re growing food.

The discussion enters all kinds of arenas, from property taxation to seed research. 

If you’re growing things, but not growing food, do you still qualify for an agricultural dedication for tax purposes? Is a gentleman’s horse ranch not an agricultural enterprise unless you’re milking the mares? Should we use taxation to punish you if your crop doesn't end up in someone's belly?

If you try to define agriculture, ultimately it gets into the Alice Through the Looking Glass discussion: “It means what I choose it to mean—neither more nor less.” 

Still, there are some standards.

Breaking down the word agriculture, you get two Greek-Latin roots, meaning land and tilling. Nothing about food. (Interesting that the agri in agriculture and acre have the same Latin root—ager, for land or field.)

Breaking down the word farm, and you pass through Middle English, old German and French terms referring to both food farming and any land management that pays the rent. Ultimately in Latin there is a sense of food and feast, but also security—like something that provides you with the means for survival, or something you can use as collateral. (Farm and firm have the same Latin root, firma, meaning solid and to be relied on.)

Small farms in the American Midwest might grow corn and alfalfa to feed cattle, and they’d raise the cattle for milk and cheese, and perhaps tobacco for a cash crop, a vegetable garden, and a managed woodlot for firewood and for woodworking. As far as the farmer was concerned, it was all farming.

Trying to define agriculture too narrowly yields endless debate.

If food crops are farming, are fiber crops not? What about medicinal crops? What about energy crops (whether trees, or cane or switchgrass)?

Is raising livestock farming, and must we distinguish between a horse that pulls the plough and the cow that offers milk? If you’re raising sheep for meat, it’s farming, but if you’re raising the same sheep for wool it’s not?

And what of the cover crop that is tilled under to improve the soil? It doesn’t directly feed people, so it is not farming? But it supports the subsequent food crop, so maybe it is? Even dedicated food farmers need sometimes to grow non-food crops—cover crops, erosion control grassed areas, windbreaks—and sometimes need to leave a field fallow.

It is a slippery slope, and trying to define it too narrowly leads to trouble, as Lewis Carroll’s Alice found:

"I don't know what you mean by 'glory'," Alice said.
Humpty Dumpty smiled contemptuously. "Of course you don't—till I tell you.

This is not to say it’s impossible to make public policy of promoting food crops—just that it needs to be done very carefully.

© Jan TenBruggencate 2014

Saturday, October 4, 2014

600-year-old Polynesian voyaging canoe found on New Zealand's South Island

For Polynesian canoe culture, the New Zealand discovery of part of a 600-year-old voyaging canoe is the equivalent of finding King Tut’s tomb.

The only other comparable discovery was when Bishop Museum’s Yosi Sinoto in the late 1970s found the remains of a voyaging canoe at Fa`ahia on the French Polynesian island of Huahine. 

(Image: The carving of a turtle is visible on the hull of an ancient Polynesian voyaging canoe found on New Zealand’s South Island. (Credit: Tim Mackrell / The University of Auckland.)

And that’s it. There are virtually no other large surviving parts of Polynesian voyaging canoes.

The latest discovery was written up in Proceedings of the National Academy of Sciences by authors Dilys Johns, Geoffrey Irwin and Yun Sung, all of the University of Auckland. The title: “An early sophisticated East Polynesian voyaging canoe discovered on New Zealand’s coast.

From a single plank nearly 20 feet long, presumably from above the keel on the back half of the canoe hull, a great deal of information was extracted. 

Two of the most fascinating features: A raised relief turtle carved into the outside of the hull; And both ribs and longitudinal stringers carved into the plank, presumably for strength but in the case of the stringer, for lashing internal frameworks.

The plank was found among driftwood after a storm on the east South Island inlet of Anaweka.

“The canoe dates to approximately A.D. 1400 and was contemporary with continuing interisland voyaging. It was built in New Zealand as an early adaptation to a new environment, and a sea turtle carved on its hull makes symbolic connections with wider Polynesian culture and art,” wrote the authors.

The canoe was built of a New Zealand tree called matai (Prumniopitys taxifolia). There were holes around the perimeter of the plank for lashing. While Hawaiian canoes were generally carved of a single hull with upper parts lashed to them, many South Pacific island groups made canoes of multiple planks that were lashed together.

The plank apparently had been safely buried in the sand dune along a freshwater stream for a long time. There was still caulking material in four of the lashing holes, made of the bark of the totara (Podocarpus totara). 

The inside of the hull showed adz marks, but the outside was smoothly polished. The hull was carbon dated to as early as the middle 1200s, but that would have been the age of the tree used to make the plank, not the age of the canoe. The caulking dated to the middle 1300s to as late as 1410.

Polynesians are believed to have arrived in New Zealand around 1200. The Anaweka canoe shows that they continued to voyage and built canoes locally once they arrived. 

“The canoe is contemporary with early archaeological settlements around New Zealand and on-going voyaging between Polynesian islands,” the authors said. In recreating the entire canoe from the shape of the stern plank, the researchers assume the canoe had been in the neighborhood of 40 to 50 feet long. There were signs of repairs, indicating it had been used over an extended period of time, and fixed when it broke.

“The age, location, size and sophistication of the find all suggest that it was from a sea-going sailing canoe, but the obvious question is what type of canoe it was,” the authors wrote.

What they concluded was that it may have been a very similar vessel to the one Sinoto found at Fa`ahia. 

“Radiocarbon dates from the (Fa`ahia) site indicate occupation in the period A.D. 1050-1450, in the same time range as the Anaweka canoe,” they wrote.

“The Anaweka and Fa`ahia canoes were unlikely to have been of the same design, but it is possible that they could have come from the same design tradition. In that sense, the evidence from two widely separated locations in East Polynesia are complementary,” the authors wrote.

“The Anaweka canoe was a large, sophisticated and powerful craft…last caulked around A.D. 1400…It was active on the exposed open sea coast of the South Island,” they concluded.

© Jan TenBruggencate 2014

Saturday, September 27, 2014

Human teeth at dig put modern humans in China 70,000 to 126,000 years ago

Humans are a traveling species, and maybe they always have been.

New evidence suggests that humans—or something very close to humans—traveled out of Africa and into Asia far, far earlier than most modern models suggests. 

(Images: Two teeth that appear likely to be from anatomically modern humans; paleoanthropologist Christopher Bae at a fossil dig. Credit: University of Hawai`i at Mānoa.)

University of Hawai`i paleoanthropologist Christopher Bae, is the lead author on a paper that reports on human remains from China that date back roughly 125,000 years.

(Citation: Christopher J. Bae, Wei Wang, Jianxin Zhao, Shengming Huang, Feng Tian and Guanjun Shen, Modern human teeth from Late Pleistocene Luna Cave [Guangxi, China], DOI: 10.1016/j.quaint.2014.06.051)

Current theory has modern humans leaving Africa 60,000 years ago, but Bae and his co-authors found human teeth dating to between 70 and 126,000 years ago. They found the material in the Lunadong cave in China’s Guangxi Zhuang Autonomous Region, north of Vietnam.

It suggests there was not just one Out of Africa migration, but at least two, and possibly several.

“The findings from the Lunadong study clearly indicate that certain aspects of the Out of Africa model need to be rethought. That is, that there was at least one other earlier Out of Africa migration event that predated 60,000 years ago. 

“This paleoanthropological find, in addition to other recent studies from western and southern Asia, suggest that modern humans may have dispersed out of Africa in multiple waves rather than as one major single migration event 60,000 years ago as commonly thought,” said Bae, in aUniversity of Hawai`i press release.

There were numerous other human-like creatures traveling the world from their African homeland far earlier than this. Neandertals, Homo erectus and others were clearly moving across the landscape. Peking Man, whose remains were found in the 1920s near Beijing, dates to more than half a million years ago. He is considered a variety of Homo erectus.

© Jan TenBruggencate 2014

Sunday, September 21, 2014

Scary stuff: Great Barrier reef growth down 40%, world (and U.S.) carbon production stll increasing

The ravages of climate change thunder onward, and recent science doesn’t provide much hope.

Coral decline has been an issue, associated with coral disease, coral bleaching and lots more. A new study indicates the problems just keep coming. And our use of carbon is (surprise!) still climbing.

(Parenthetically, it’s election season. You need to ask every candidate whether they deny climate change, in which case don't vote for them, And more importantly, ask what they’ll do to combat it. And vote accordingly.)

A 30-year study of Australia’s Great Barrier Reef shows that coral growth has dropped an astounding 40 percent. Here is the ScienceDaily story on that. 

The abstract of the paper, published in the journal Geochimic et Cosmochimica Acta, suggests pretty clearly that ocean acidification—a result of increased carbon dioxide in the atmosphere—is the cause: 

“The similarity between the predicted and the measured decrease in (calcification) suggests that ocean acidification may be the primary cause for the lower CaCO3 precipitation rate on the Lizard Island reef flat.”

We're not aware of similar studies in the Hawaiian Islands, but it's reasonable to conclude that if it's happening on the largest reef system in the world, it might be happening elsewhere.

And, for all the talk, we’re not having much of an impact on the problem. Carbon dioxide emissions by human activities, far from declining or even staying level, are increasing. 

They're increasing more than the global average in the United States, India and China. The European Union has decreased carbon release, although it continues to import large amounts of goods from China, so it effectively shifts some of its carbon production there.

This is, of course, maddening. It’s like being on a careening bus, headed for a cliff, and being unable to agree to use the brakes.

A new study by the United Kingdom’s Tyndall Centre for Climate Change Research and the College of Engineering, Mathematics and Physical Sciences at the University of Exeter, says carbon dioxide releases into the atmosphere will rise in 2014 by another 2.5 percent, to 40 billion tonnes.

As the Great Barrier Reef inquiry and myriad other studies show, the results are bad already. But they can and will get worse. Many scientists feel that 2 degrees Celsius is a tipping point for catastrophic change.

"We have already used two-thirds of the total amount of carbon we can burn, in order to keep warming below the crucial 2°C level. If we carry on at the current rate we will reach our limit in as little as 30 years' time–and that is without any continued growth in emission levels. 

"The implication of no immediate action is worryingly clear—either we take a collective responsibility to make a difference, and soon, or it will be too late," said Pierre Friedlingstein, a professor at Exeter and lead author of the paper. 

Need some data points? This is from a press release from the University of East Anglia:

    China's CO2 emissions grew by 4.2 per cent in 2013, the USA's grew by 2.9 per cent, and India's emissions grew by 5.1 per cent.
    The EU has decreased its emissions by 1.8 per cent, though it continues to export a third of its emissions to China and other producers through imported goods and services.
    China's CO2 emissions per person overtook emissions in the EU for the first time in 2013. China's emissions are now larger than the US and EU combined. 16 per cent of China's emissions are for goods and services which are exported elsewhere.
    Emissions in the UK decreased by 2.6 per cent in 2013 caused by a decline in the use of coal and gas. However the UK exports a third of its emissions by consuming goods and services which are produced elsewhere.
    CO2 emissions are caused primarily by burning fossil fuels, as well as by cement production and deforestation. Deforestation accounts for 8 per cent of CO2 emissions.
    Historical and future CO2 emissions must remain below a total 3,200 billion tonnes to be in with a 66 per cent chance of keeping climate change below 2°C. But two thirds (2,000 billion tonnes) of this quota have already been used.
    If global emissions continue at their current rate, the remaining 1,200 billion tonnes will be used up in around 30 years – one generation.
    Global emissions must reduce by more than 5 per cent each year over several decades to keep climate change below 2°C.
(Here is the citation for the coral study: J. Silverman, K. Schneider, D.I. Kline, T. Rivlin, A. Rivlin, S. Hamylton, B. Lazar, J. Erez, K. Caldeira. Community calcification in Lizard Island, Great Barrier Reef: A 33 year perspective. Geochimica et Cosmochimica Acta, 2014; DOI: 10.1016/j.gca.2014.09.011)
© Jan TenBruggencate 2014