The comeupance of New Mexico host one of Americas most innovative pre - colonization civilizations , including the oldest surviving building in what is now the United States . This vex late arrivals since the area is a crude contrast from the profuse river valleys and productive farmlands that gave rise to enceinte urban center elsewhere . Now a fond explanation has emerged in the strain of lava electron tube , which apparently allowed people to survive the region ’s harsh drouth .
To Spanish explorers , westerly New Mexico was so uninviting they called it El Malpais , the unsound land . Yet the people who lived there , known as theAncestral Puebloans , were numerous enough to build multi - story “ great houses ” . To do so they must have had access to urine supplies that lasted through multi - yr droughts .
Exploring a lava tube in El Malpais National Monument , Professor Bogdan Onacof the University of Southern Florida found what he think is the account . Even today the tube is make full with internal-combustion engine – reflecting its altitude of 2,268 measure ( 7,500 feet ) above sea level and the mode the cave shape draws in cold air and forces out warmth .
Bogdan discovered charcoal deep in the tubes , which he has found dates to between 1,970 and 1,070 years old , with one further deposit around 600 years ago , long after the nearby great house had been abandon . He realize people brought wood they could burn into the cave and used the high temperature to melt down glass , and must have either left the cave while the mental process was afoot to avoid dying of smoke intake or carefully managed the firing size . Although Onac acknowledges there could have been spiritual import to these fires , the melted urine would sometimes have been all that stood between the Ancestral Puebloans and end from hungriness .
InScientific Reports , Onac break that the date of the charcoal deposits match those of major droughts derived from Sir Herbert Beerbohm Tree pack and lake sediments elsewhere in the American West . " This find disgorge twinkle on one of the many human - environs interaction in the Southwest at a metre when climate change wedge people to recover water resource in unexpected spot , " Onac said in astatement .
The tube where the breakthrough was made , know as Cave 29 , is just one of 453 be intimate in the ancient volcanic province .
As exciting as the breakthrough is for archeologist , it add up about for disturbing rationality – the frosting is now melting faster than it ever did when multitude by choice encouraged the process . “ The melting cave ice under current climate conditions is both uncovering and threatening a flimsy source of paleoenvironmental and archaeological evidence , " Onacnoted . The remnant meth is a small portion of what once fill up a declamatory lot of the cave .
Onac believe that in ordinary years the ice would have fade of its own accord , leave pools near the entering that the Ancestral Puebloans could imbibe from . During dryer period the frosting would have retreated , as whatever melted was not replaced by water filtering through fissures in the stone . This would have force those subject on the water to go into the cave , start fires , and carry what they melt out . Along with the charcoal , Onac found a sherd of pottery . Charcoal has been found in many of the other lava subway system , but not in the copiousness of Cave 29 .
