Monday, December 03, 2007

The Anthropology of Catastrophe: Volcanoes

Humans have always been afflicted by natural catastrophes ranging from tectonic to weather related and, possibly, even impacts from space! But none, perhaps, have found the significance both culturally and destructively, as the volcano. Throughout the history and prehistory of man, volcanoes have erupted, obliterating entire islands, destroying settlements and cities, ruining local crops and affecting climate on a global scale. And, while volcanoes have also long been anthropomorphized to attribute blame or malevolent intent, not a single one ever intended to cause human destruction.

Notable volcanic eruptions in the archaeological and historical record include Thera, Vesuvius, Mt. St. Helens, and Mt. Pinotubo, among many others.

Erupted 79 CE – Pompeii and Herculaneum, Italy
This was the first documented volcanic eruption in history and was responsible for the instantaneous deaths of thousands who found themselves in the path of the eruption’s heat, poison gases, pyroclastic flows of rock and ash, and the sheer trauma of the blast wave. As most people who have heard of Pompeii are no doubt aware, the site is often billed as an archaeologists’ dream since it represents a “snapshot” in time. The main reason is that settlements like Pompeii and the closer Herculaneum were inundated with volcanic ash and rock in a rapid and hot pyroclastic flow, trapping some residents in death poses until excavated nearly 2000 years later. Recent discoveries at Herculaneum include a wooden throne, preserved in the volcanic ash for over 1900 years.

Thera (Santorini)
Erupted 1627-1600 BCE Aegean Sea
Generally accepted to have brought about the demise of the Minoan civilization and ash layers from the eruption are evident in localities like Crete, and the Santorini archipelagos which includes Thera. The Minoan civilization spread across each of these and other Cycladic islands, with Crete being about 100 miles from Thera. In the Satorini archipelago is Akrotiri, a Minoan settlement buried by the 17th century BCE eruption in volcanic ash. Desturction from this eruption was primarily caused by pyroclastic flow, tsunami and ash deposits. For Minoan settlements on Thera and the Santorini island chain, civilization ended abruptly as they were vaporized, cooked, and buried alive. For the Minoan cities and settlements further away in Crete, they may have had a few more moments until the tsunami created by the massive amount of ash, rock, and other ejecta suddenly plunging into the sea, displacing the water. And, while some Minoan settlements did survive, the eruption of Thera is considered to have contributed greatly to the civilization's demise.

Mt St Helens and Mt Pinotubo
Erupted in 1980 in Washington, USA and 1991 on the Philippine Island Luzan, respectively
Mt. St. Helens was considered a major volcanic eruption, responsible for 57 deaths and thousands made homeless, not to mention the devastation to the environment. However, it small in comparison to its 20th century colleague Mt. Pinotubo, which erupted in the Philippines just a decade later. This one took 800 lives and left 100,000 or more homeless. The Pinotubo eruption was also 10 times larger than that of Mt. St. Helens. In the case of both of these eruptions, scientists and researchers were carefully monitoring the geologic activity associated with the volcanoes and were able to use the data to evacuate and warn local residents. Indeed, of the 800 killed by Pinatubo, the majority lost their lives due to the ash fall which mixed with rain and caused roofs to collapse.

In the case of each eruption, the cultural effects included the cost of rebuilding and recovering infrastructure and private property. The St. Helens eruption cost $1.1 billion to recover from the catastrophe. The residents of Luzon only faced about half that cost, but they, perhaps, suffered far more economically since the Luzon economy was ruined. Clark Air Base, which the U.S. occupied was evacuated and the Air Force never returned, which, by itself, would have spelled trouble for the local economy. The last I heard, the region is still trying to recover the economy and rebuild infrastructure.

How volcanoes destroy
Lava Flows
Although instantly associated with volcanoes, lava flows only account for a fraction of a percent of the total number of deaths due to volcanoes in the last xx years. Lava is slow and can be outrun, but it does damage property and infrastructure in places such as Hawaii where the Kilauea volcano regularly spews forth a basaltic magma that becomes lava as it leaves the ground.

These kill slightly more people than lava. Denser than air carbon dioxide and hydrogen sulfide are the most dangerous as they flow into and fill low lying areas. Carbon dioxide is colorless and odorless and can asphyxiate people who breath it unawares. Hydrogen sulfide has a "rotten egg" smell, but a single breath can kill in high enough concentrations. Fortunately, such concentrations are relatively rare. Other gases can also be problematic for humans, albeit indirectly. In 1783, the laki fissure eruption killed an estimated 10,000 Icelanders, but due to starvation and famine after the loss of crops and livestock due to long-term exposure to hydrogen fluoride.

Tephra, Ash, and pryoclastic flows
Tephra includes the fragmented rocks and blocks ejected in the air by the eruption itself. Fortunately, tephra and ash typically affect the regions closest to the volcano, having increasing less effect the further from the eruption you go. Ash, however, can be ejected high into the atmosphere, allowing it to be deposited many miles away. But its that ash and rock that lands near the volcano that is the most problematic. Much of the tephra and ash comes back down into the volcano's crater, but this often results in pyroclastic flow which can leave a wake of destruction in its path as hot ash and rock are forced down and out away from the volcano's cone due to the force of the eruption.

Relatively few people have actually lost their lives due to tephra and ash falls, however, the danger ash poses most is the accumulation on the roofs of homes and buildings, particularly if the ash becomes wet. Wet ash soaks up water, and creates a very heavy mud, about 10 inches of which are sufficient to collapse a roof, injuring or killing the building's occupants.

Pyroclastic flows have claimed far more victims, however, making this one of the more dangerous features of a volcanic eruption. 27 percent of the lives lost in recorded volcanic eruptions were due to pyroclastic flows, the effects of which are most notable in Pompeii and Herculaneum, where pryroclastic flows of ash, rock, gases, and bits of lava quickly rushed in along the ground, burying both cities. Residents had seconds to realize what had occurred, and probably each killed instantly as the heat from the flows cooked their bodies and boiled their brains -the ash burying them along with the buildings, homes, and artifacts of their cities. Alun Salt discusses a recent find of a throne at Herculaneum at Clio Audio, describing the effects of pyroclastic flows and preservation of material remains.

Lahars and Tsunamis
Another immediate killer from volcanic eruptions are the occasional lahars as well as the tsunamis some volcanoes create due to earth quakes caused by the eruption or pyroclastic flows that dump into the sea, displacing water. Lahar is an Indonesian word that refers to the mud flows created by large amounts of ash and water. The heat from a volcanic event can melt snow and ice and, as the resulting water mixes with ash, a mud is formed which then flows down the mountain, obliterating towns and settlements. Lahars and tsunamis are together responsible for a whopping 34% of the deaths that have been recorded due to volcanoes.

But that isn't the most significant killer that results from a volcano. The most significant killer is, by itself, responsible for a full 30% of the deaths related to volcanoes (remember, lahars and tsunamis are two different things -17% each). That killer is post-eruption famine and disease that takes place months later. Gases and ash ejected into the atmosphere can affect crops and livestock and even global temperatures! 1816 was called the "year without summer" due to the eruption of Tambora in Indonesia the year before. Global temperatures dropped to between .4 and 1.0 Celsius and crops were affected around the globe. In Europe, particularly in Great Britain, a typhus epidemic that broke out that year was blamed on the unseasonably cold weather.

Volcanoes and Human Belief, Religion, and Superstition
Volcanoes don't seek human attention or appeasement. But its easy to see how others might think so. Humans have long had very tenuous relationships with their volcanoes, which remain oblivious to the anthropomorphizing applied by cultures in South America, Indonesia, Polynesia, and Mesoamerica. Volcanoes gods exist in many cultures even today and many sacrifices have been made to these gods in the way of virgins and material possessions in attempt to appease the god.

Perhaps the most familiar volcano god to Americans is Pele, since this legend is still told (albeit mostly tongue-in-cheek) in the state of Hawaii where the Kilauea volcano is still active. According to the legend, Pele is the goddess that lives in the volcano and she created (and is still creating) the islands of Hawaii.

In Japan, Mt. Fuji is the source of several myths and legends, including that the goddess Sengen resides there, tossing off the mountain any pilgrim of impure heart. Legend has it that the mountain was created in a single day at around 86 BCE, though the mountain itself can be geologically dated to as far back as 8500 BCE when it was volcanically created. There was, however, an eruption at around 86 BCE, which may have inspired the legend of its creation.

The myth of Atlantis, a story first created in two dialogs by Plato, may have had its inspiration in the oral stories that surrounded the fall of the Minoan civilization and the sudden demise of several of their cities. If true, Plato certainly embellished the account and modified it to fit the the lesson he was trying to teach through Critias and Timaeus, the two dialogs in which he mentions Atlantis. It is fascinating to consider the appeal that the story has on even modern humans and their beliefs.

Finally, it mustn't be overlooked that the very term "volcano" and the study of volcanoes, "volcanology," is derived from Vulcan, the Roman god of fire.

One might ask why bother living near such an unpredictable god? One reason, of course, is that the god provides a bounty by way of rich soils for cultivation and other resources such as an abundance of chert and obsidian needed for manufacture of stone tools.

For all the difficulties volcanoes have created for man, we, perhaps, have reaped far more benefit.

Additional reading

Appeasing the Volcano Gods
Feldman, Joanne and Robert I. Tilling (2007). Danger Lurks Deep: The Human Impact of Volcanoes. Geotimes, 52(11), 30-35.

4 Epigraphic Artifacts:

Alun said...

You might also be interested in Te Wairoa in New Zealand.

CFeagans said...

I'm checking it now! The topic on the human impact of volcanoes (and other catastrophes) is a fascinating one and I found myself having to set some limitations or my post would have been MUCH longer.

Still, it leaves some material to return back to in the future. Interestingly enough, I stumbled on your Herculaneum post during the process of writing this and verifying some dates.

Anatoly said...

Where did you get the statistics for what features of a volcanic eruption kill what percentage of people?

CFeagans said...

[b][i]Where did you get the statistics for what features of a volcanic eruption kill what percentage of people?[/i][/b]

From the current edition of Geotimes. The exact article is listed above. I'm not sure what the authors' sources are, however. Though it may be referenced in the article. I'll check.

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