Too small to fail

Pasatiempo - - Mixed Media - Paul Wei­de­man The New Mex­i­can

We usu­ally think of ar­chae­ol­o­gists as dig­ging up and record­ing rem­nants of past civ­i­liza­tions, but in­ter­pre­ta­tion is an­other im­por­tant part of the sci­en­tists’ work. When Ari­zona ar­chae­ol­o­gist Mark El­son in­ves­ti­gated pre­his­toric sites along the route of a planned high­way ex­pan­sion, he not only un­earthed pot­sherds, stone tools, and other ar­ti­facts, but he also found ev­i­dence of a suc­cess­ful mass re­set­tle­ment of peo­ple fol­low­ing the erup­tion of an an­cient vol­cano.

The de­tails of that adap­ta­tion to a catas­tro­phe that took place about 900 years ago may help pre­vent hu­man losses due to vol­ca­noes, earth­quakes, and hur­ri­canes to­day. El­son, a project di­rec­tor at Tuc­son-based Desert Ar­chae­ol­ogy Inc., is the lat­est speaker in the South­west Sem­i­nars se­ries An­cient Sites & An­cient Sto­ries. His topic for a Mon­day, May 17, lec­ture in Santa Fe is “Hu­man Adap­ta­tion to Cat­a­strophic Events: Lessons from the 11th Cen­tury A.D. Erup­tion of Sun­set Crater Vol­cano.”

The re­search re­lated to his talk be­gan when his com­pany won the con­tract to doc­u­ment 40 pre­his­toric sites along U.S. 89 be­tween Flagstaff and the Utah border. Be­gin­ning in 1998, El­son worked with vol­ca­nol­o­gists and ge­o­mor­phol­o­gists from North­ern Ari­zona Uni­ver­sity and with rep­re­sen­ta­tives of the Hopi Tribe, pur­su­ing two lines of in­quiry. One was to il­lu­mi­nate the de­tails of an ap­par­ently suc­cess­ful adap­ta­tion to the erup­tion of Sun­set Crater Vol­cano (about five miles east of the high­way) by lo­cal peo­ple — the Si­nagua, as 1930s ar­chae­ol­o­gist Harold Colton called them. The other was to try to con­firm the re­la­tion­ship of those peo­ple to the Hopi.

“Sun­set Crater was an ex­am­ple of a par­tic­u­larly good adap­ta­tion,” El­son said by phone from his of­fice at Desert Ar­chae­ol­ogy. “The peo­ple not only sur­vived but thrived and ended up build­ing some of the largest Pue­blo struc­tures in the Flagstaff area.”

An im­por­tant find­ing of the U.S. 89 team was that, af­ter the erup­tion, a thin layer of vol­canic cin­ders acted as a wa­ter-re­tain­ing mulch on the land­scape. This “cin­der mulch” opened to farm­ing large ar­eas that pre­vi­ously had no agri­cul­tural value. The Si­nagua peo­ple flour­ished there, build­ing an im­pres­sive rock-walled pue­blo whose ru­ins to­day are the show­case of Wu­patki Na­tional Mon­u­ment.

El­son said the peo­ple were able to adapt to the vol­canic catas­tro­phe be­cause of a num­ber of preadap­ta­tions. “They lived in very small groups, with the largest sites hav­ing only 30 to 50 peo­ple. They likely had a large kin net­work out­side of the erup­tion area, and they had a limited so­cial hi­er­ar­chy, so de­ci­sion-mak­ing was done at the house­hold level or a level just above that. So they could make the de­ci­sions and move eas­ily.

“Also, they didn’t have a lot in­vested in their in­fra­struc­ture; they could eas­ily re­build their houses within a cou­ple of weeks. They al­ready knew how to grow crops, and be­cause of the scant rain and grow­ing sea­son, they had a risk-re­duc­tion strat­egy, do­ing lots of small plots in mi­cro-en­vi­ron­ments, so an erup­tion might not dam­age all their crops.”

An­other fac­tor was that this catas­tro­phe was a vol­canic erup­tion, and vol­ca­noes don’t blow up with­out warn­ing. Lo­cal earth­quakes warn that an erup­tion is im­mi­nent. Peo­ple in Mi­choacán, Mex­ico, felt quakes be­gin 45 days be­fore Parí­cutin Vol­cano started erupt­ing in 1943. The tremors grad­u­ally in­creased in fre­quency un­til, the day be­fore the blast, 300 small quakes oc­curred.

The erup­tion of Parí­cutin, which is con­sid­ered a “twin” to Sun­set Crater Vol­cano be­cause of its sim­i­lar type, had an im­mense im­pact on thou­sands of the na­tive Purépecha (Taras­can) peo­ple. The erup­tion cov­ered nearly 10 square miles with lava and an­other 70 square miles with ash and cin­ders too thick for agri­cul­ture to be done. But no­body died in the erup­tions, which lasted al­most 10 years.

El­son and North­ern Ari­zona Uni­ver­sity’s Michael H. Ort, his chief col­league on the U.S. 89 project, ob­tained a grant that al­lowed them to visit Mi­choacán in 2003. El­son in­ter­viewed peo­ple about the erup­tions, and the two col­lected sam­ples from older trees in the area. The sam­ples, with help from tree-ring anal­y­sis and a process called “laser ab­la­tion in­duc­tively cou­pled plasma mass spec­trom­e­try,” showed el­e­vated lev­els of cer­tain chem­i­cals typ­i­cally thrown into the air dur­ing vol­canic erup­tions. That technology, which was used to an­a­lyze wood sam­ples from the Parí­cutin erup­tions, is be­ing em­ployed at Sun­set Crater.

“We’re still work­ing on this, but we think the erup­tion oc­curred in the A.D. 1080s,” El­son said. “There’s an old, fa­mous A.D. 1064 date that came out of re­search done in 1958, but our team dis­putes the ev­i­dence. True, it’s only a 20-year dif­fer­ence, but it is a big dif­fer­ence in terms of hu­man adap­ta­tion. The ear­li­est date we have for Wu­patki is 1106, and if the erup­tion was 1064, that’s [al­most] 50 years, so you won­der, why did they wait 50 years to re­set­tle down there? The ar­gu­ment is that maybe they didn’t un­der­stand the cin­der mulch, but I don’t buy that. These peo­ple lived in a cin­der field. There are 600 cin­der cones in the area, and they had done agri­cul­ture there.

Parí­cutin Vol­cano erup­tion, circa 1943; photo by Ted Ni­chols

Ex­ca­vated roomblock at the Homestead site (NA 181), which was oc­cu­pied from 1075 to 1150 A.D., dur­ing the era of the Sun­set Crater erup­tion

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