Archaeology and Volcanism|
II. Herculaneum and Pompeii: Cities of the Early Roman Empire
A. Historical Significance
Pompeii, in A.D. 79 a thriving commercial center of about 20,000 inhabitants, and Herculaneum (Fig. 1 and Fig. 2) a largely residential town of about 5000, are uniquely important. Frozen in time, they offer a superbly detailed picture of life in the early Roman Empire, encompassing temples, theaters, shops, private houses, gardens, fountains, public baths, swimming pools, and a miraculously preserved library. Interred so swiftly that most residents had no time to save their possessions, the ruins contained a rich variety of rare items, including gold jewelry, silver dishes, the most complete known set of Roman surgical instruments, and even wax tablets inscribed with bank records. Recovery of Greco-Roman statuary, paintings, and furniture influenced 18th and early 19th century art and architecture throughout Europe and America, where Thomas Jefferson modeled Monticello on classical styles.
FIGURE 1 Whereas most buildings in Pompeii are roofless, crushed by the accumulation of tephra from Vesuvius, many of Herculaneum's structures, such as these small shops, retain their upper stories. An affluent resort town on the Bay of Naples, Herculaneum is perhaps the best-preserved urban site of the early Roman Empire. (Photo courtesy of Dr. James Straukamp.)
B. Recent Discoveries at Herculaneum
Besides their historical role as a testing ground for new archaeological techniques and concepts of preservation, Pompeii and Herculaneum continue to yield invaluable information about the Roman world, including the physical attributes of the cities' former inhabitants. Until the early 1980s, when about 130 largely intact skeletons were exhumed along Herculaneum's former waterfront, it was assumed that most of Herculaneum's population had managed to escape the city alive. The discovery of so many well-preserved remains is particularly important because the Romans, who typically cremated their dead, otherwise have left little evidence of their bodily characteristics. Caught in the fierce heat and swirling ash of a pyroclastic surge, the victims had apparently been asphyxiated while attempting to flee by boat. (An overturned 30-foot wooden vessel was found nearby.) The skeletal remains at Herculaneum are considered invaluable because they encompass individuals of all ages and classes, ranging from a bejeweled Roman matron to a teenaged slave girl to a middle-aged soldier, sword in hand, whom the surge had thrown to the ground face-down. Hundreds more skeletons may still await discovery.
FIGURE 2 Engulfed by pyroclastic flows during the A.D. 79 eruption of Mount Vesuvius, the Roman town of Herculaneum has been only partially excavated. Property owners of the modern town of Resina, built atop the site, effectively prevent further excavation. (Photo courtesy of Dr. James Straukamp.)
C. Sequence of Eruptive Events in A.D. 79
The effects of Vesuvius's outburst on the nearby human population are now better understood than those of any other ancient volcanic disaster. Not only did a remarkably observant Roman nobleman, Pliny the Younger, write two letters to the historian Tacitus in which he carefully described Vesuvius's behavior, but modern volcanologists led by Haraldur Sigurdsson have been able to correlate Pliny's account with particular strata deposited by the eruption. The eruptive sequence, and its effects on the human population, is now well understood. After some preliminary activity, which dusted one slope of the volcano with a light tephra fall, the main eruption began about 1 P.M., August 24 with an explosive discharge of pumiceous ash, forming an ash column that, in Pliny's words, resembled a towering pine tree with spreading upper branches. For the next 11 hours, Vesuvius ejected a vertical eruption cloud (called Plinian after the Roman author who first described the phenomenon) that rose approximately 12 miles into the stratosphere. Carried south-southeastward by the prevailing winds, the ash canopy enshrouded Pompeii, extinguishing sunlight and raining lapilli (the Latin term for small stones) over the city, where pumice accumulated at the rate of 6 inches per hour. Lying four miles upwind from Vesuvius, Herculaneum received only a trace of ash during this phase of the eruption.
Shortly after midnight, however, the character of the eruption abruptly changed. As Vesuvius tapped deeper levels of its magma chamber, the gas-rich volatile mixture that had sustained the Plinian cloud became increasingly depleted, causing the ash column to collapse. Expanding horizontally, the turbulent ash cloud separated into a fast-moving pyroclastic surge that swept through Herculaneum, killing all who remained there, and a somewhat slower-moving pyroclastic flow that enveloped the town, initiating its burial. As the eruption column continued to fluctuate, a second surge and pyroclastic flow were generated an hour later. A third, at 5:30 A.M. on August 25, finished the work of entombing Herculaneum under a hot ash deposit tens of feet thick.
The third pyroclastic flow, which had interred Herculaneum, was deflected from Pompeii by the city's massive walls. The fourth, however, exhibited lethal energy, racing 6 miles from Vesuvius's crater and blasting through the city like an incandescent sandstorm. Rushing across the 7-foot thickness of pumice that had previously fallen, the flow toppled exposed walls, sheared off roofs and upper stories of buildings, and asphyxiated the remaining inhabitants.
Trapped in the fourth pyroclastic flow, thousands of fleeing Pompeiians were instantly entombed. When their bodies decayed, they left behind hollow spaces in the ash. Recognizing that these cavities were, in effect, molds of human figures, 19th century archaeologists filled them with liquid plaster, allowed it to solidify, and then removed the surrounding ash. The plaster casts thus formed are astonishingly lifelike, some showing in detail the agonized facial expressions of the volcano's victims.
In 1961, archaeologists unearthed a particularly poignant group in a location called the Fugitives Garden, where casts were made of seven adults and six children. Like many of the 57 people killed in the 1980 pyroclastic surge from Mount St. Helens, the fugitives appeared to have died of suffocation from inhaling the pervasive ash. Estimates of the fatalities in Pompeiisome archaeologists state that about 2000 perishedwere based on the number of skeletons found in the lower pumice deposits and the body-shaped cavities formed in the upper pyroclastic flow deposits. With the realization that the pyroclastic surges and flows probably killed simultaneously many of the people who were fleeing along the roads outside Pompeii's city gates, historians now believe that many more thousands perished in the disaster.
At 8:30 A.M. on August 25, Pliny witnessed the generation of the sixth and largest pyroclastic surge, "a fearful black cloud ... rent by forked and quivering bursts of flame" that swept across the Bay of Naples toward Misenum, located 20 miles west of Vesuvius. Fleeing the city with hoards of panicked refugees, Pliny noted that "many besought the aid of the gods, but still more imagined there were no gods left, and that the universe was plunged into eternal darkness for evermore."
D. Rediscovery and Excavation
Although some survivors later burrowed into the deposits covering Pompeii, retrieving valuable objects and even building materials, the buried cities eventually became almost entirely forgotten until 1709, when laborers digging a well happened upon Herculaneum's theater. Despite being rediscovered first, most of Herculaneum still lies underground, embedded in pyroclastic flow deposits that hardened to the consistency of cement. Besides the enormous difficulty of removing the solidified ash enshrouding the site, landowners in the modern town of Resina, which sprawls atop the deposits covering Herculaneum, refuse to permit archaeologists to expand the excavations.
Beginning in 1738, excavators bored a network of tunnels through part of the town, haphazardly looting statuary and other portable art and carelessly wrecking any structure considered uninteresting. One of the most promising 18th century finds was an elaborate residence known as the Villa of the Papyri, which sheltered a library of 1800 carbonized scrolls. Hopes that this collection would yield literary masterpieces, such as a lost tragedy by Sophocles, were dashed when most of it turned out to be the work of a minor Epicurean philosopher, Philodemus. The villa's presumed owner, L. Calpurnius Piso, the father-in-law of Julius Caesar, was Philodemus's patron.
Today most of the 18th century tunnels burrowing through underground Herculaneum are closed, and visitors can no longer walk across the theater's ancient stage. Even though most of Pompeii has been opened to light and air, Herculaneum remains largely buried, its mysteries still hidden. The few buildings now exposed, such as the elaborate suburban baths, represent only a fraction of structures waiting to be discovered, along with an unknown number of sculptures, paintings, and scrolls.
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