WORLD

Is it possible to walk through the gates of hell and live? Ancient Romans thought so, and they staged elaborate sacrifices at what they believed were entrances to the underworld. How did that work? (Science)

Learn a little about Ancient Rome, and why “gates to hell” are still deadly today.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit, including today’s MapMaker Interactive map.

Discussion Ideas

• The fabulous new research outlined in the Science article describes the plutonium at Hierapolis, a 2,200-year old structure in what is now southwestern Turkey. What is a plutonium?
  • A plutonium is part of a temple or sanctuary dedicated to Pluto, the Roman god of the underworld. A plutonium is sometimes called a ploutonion or, more dramatically, a “Gate to Hell.” According to the Science article, these entrances to the underworld were sprinkled throughout temples in the Mediterranean basin.
  • The gate to hell in Hierapolis “is a stone doorway leading to a small cave-like grotto. The gate was built into one wall of a rectangular, open-aired arena, topped by a temple and surrounded by raised stone seating for visitors.” The Science article has a nice reconstruction here.
    • Rituals performed at the plutonium included the sacrifice of animals. Priests of Pluto would lead sacrificial cattle, goats, sheep, and songbirds down the misty, mysterious stone passageway, where the animals would perish. The priests survived.
  • When the Hierapolis plutonium was established, about 190 BCE, the city was part of a kingdom in the Roman sphere of influence. It remained a part of the Roman Empire until about the fifth century CE, when it was absorbed into the Byzantine Empire.
    • Today, the hot springs, pools, and ancient ruins at Hierapolis are a UNESCO World Heritage Site.

 

• According to the new research, how was physical geography responsible for the deaths of sacrificial animals at the plutonium at Hierapolis? Read through this short article on a modern-day tragedy for some help.
  • carbon dioxide emissions. Hierapolis sits on a very volcanically active area, one prone to “degassing.” The degassing process is one in which the area’s shallow magma chamber releases its volatile gases when put under pressure by tectonic activity.
    • A natural vent beneath the plutonium constantly emits carbon dioxide, a deadly volcanic gas. The carbon dioxide pours forth as visible mists, which were thought to reflect the breath of Pluto himself “and/or the breath of the hellhound Kerberos guarding the entrance to hell.”
    • Near the floor of the plutonium, carbon dioxide is emitted in concentrations of up to 91%. (!) “During the day, the sun’s warmth dissipates the gas. But at night the gas—slightly heavier than air—billows out and forms a CO2 ‘lake’ on the sheltered arena floor. It is particularly deadly at dawn, when the CO2 concentration 40 centimeters (16 inches) above the arena floor reaches 35%.” These are concentrations “that would easily kill even a human being within a minute.”

 

• Could other “gates to hell” across the Mediterranean work the same way? Check out today’s simple MapMaker Interactive map for some help.
  • Yes. The Mediterranean basin is incredibly tectonically active, and the site of dozens (if not hundreds) of earthquakes and incidents of volcanic activity every year. The most massive tectonic actions are the African and Arabian plates moving northward and ultimately subducting beneath the Eurasian plate.
    • Hierapolis sits on the Anatolian microplate, which interacts with all three much-more-massive tectonic plates.
      • To the north, the Anatolian plate has a transform boundary with the Eurasian plate.
      • To the east, the Anatolian plate has a transform boundary with the Arabian plate.
      • To the south, the Anatolian plate has a convergent boundary with the African plate.

 

• If the concentrations of carbon dioxide were enough to kill a person in a minute, how did the priests at Hierapolis avoid death?
  • They were taller than the sacrificial animals. The carbon dioxide “lake” was a little more than a foot deep. “Sacrificial animals were not tall enough to keep their heads fully clear of the CO2 lake, and as they became dizzy, their heads would have dropped even lower, exposing them to higher CO2 concentrations and leading to death by asphyxiation. The priests, however, were tall enough to keep their heads above the dangerous gasses, and may have even stood on stones to add to their height.”

 

• Is the plutonium at Hierapolis still emitting its deadly “breath” today, or has volcanic activity slowed in the intervening millennia?
  • It’s still deadly. “Astonishingly, these vapors are still emitted in concentrations that nowadays kill insects, birds, and mammals” (mostly mice) that wander too close to the early-morning mists.

 

• This research is so, so cool. What makes it exciting for multidisciplinary scholars?
  • The research “proves the veracity of ancient sources and helps explain not only why people could enter, but also why animals would die.” It “strongly corroborates that at least in the case of Hierapolis, ancient writers like Strabo or Plinius described a mystic phenomenon very exactly without much exaggeration.”
    • This makes it of interest to geologists, classicists, chemists, historians, and, of course, geographers.

 

TEACHERS TOOLKIT

Science: This Roman ‘gate to hell’ killed its victims with a cloud of deadly carbon dioxide

Nat Geo: Plutonium at Hierapolis map

Nat Geo: Ancient Rome

Nat Geo: Volcanic Gas Kills Thousands article

UNESCO World Heritage Center: Hierapolis-Pamukkale

(extra credit! paywalled) Archaeological and Anthropological Sciences: Deadly CO2 gases in the Plutonium of Hierapolis (Denizli, Turkey)