Chapter 1: The Mediterranean's Dramatic History

The Mediterranean Sea has played a pivotal role in the narratives of numerous civilizations. It served as the battleground for the First Punic War between Rome and Carthage and was the site of the crucial Battle of Salamis, which altered the course of history between Greece and Persia. In contemporary times, it was also the location of the first-ever aircraft carrier attack, targeting the Italian port of Taranto. Yet, its significance extends beyond warfare; the Mediterranean holds stories of ambition, such as the fantastical dreams of German engineer and Nazi party member Herman Sörgel, who envisioned draining the sea to cultivate farmland for humanity's benefit.

While the Mediterranean can recount countless incredible tales, perhaps its most remarkable story is one of its own origin. Instead of a gradual formation, a theory suggests that the Mediterranean Sea emerged through a rapid and violent process—almost akin to a watery Big Bang.

The events leading to this extraordinary birth date back over five million years, beyond the reach of any eyewitnesses. However, researchers have unearthed compelling evidence of a colossal flood beneath the sea floor. This flood was so immense that "cataclysmic" might be a more fitting description.

This riveting narrative is not recounted by historians but by scientists, particularly geophysicist Daniel Garcia-Castellanos from the Institute for Earth Science Jaume Almera in Barcelona, Spain. Should this theory hold true, it would represent the largest flood in the history of our planet, as reported by Nature.

Before delving into the flood itself, we must first comprehend the circumstances that led to it. The story begins with a significant retreat of water, evidenced by extensive salt layers found at the Mediterranean's bottom.

Section 1.1: The Messinian Salinity Crisis

"Approximately 5.96 million years ago, the connection between the Atlantic and the Mediterranean was severed, triggering what is known as the Messinian Salinity Crisis. This crisis endured for over half a million years until the Atlantic once again flowed into the Mediterranean. The term 'Messinian Salinity Crisis' arises from the fact that the closure of the strait resulted in the Mediterranean evaporating faster than rivers could replenish it, creating pockets of salt up to 3–5 kilometers deep."

— On the Ocean: The Mediterranean and the Atlantic from Prehistory to AD 1500, Sir Barry Cunliffe

Nearly six million years ago, for reasons still unclear, the Atlantic Ocean's connection to the Mediterranean was lost. In the 1970s, geologist Mike Sowden revealed the discovery of massive salt deposits at the Mediterranean's floor. As seawater evaporates, it leaves behind salt and other sediments.

This is one of many reasons why Sörgel's vision of draining the Mediterranean to cultivate land would have been impractical; salt is far from ideal for farming. Some of these deposits are found to be two miles thick, forming extensive continuous layers of salt on the sea floor, indicating a significant evaporation event of epic proportions. Additional gypsum deposits along the coast further support this theory.

While Garcia-Castellanos and his colleagues note in their paper in Earth-Science Reviews that this is merely one interpretation, the actual appearance of the area during this time remains uncertain. Yet, signs suggest that some marine life persisted, implying the existence of saltwater lakes of unknown dimensions. Some scientists believe a narrow land "plug" held back the vast Atlantic Ocean—a scenario that feels straight out of a high-budget disaster film.

Section 1.2: The Zanclean Mega Flood

According to Daniel Garcia-Castellanos, the flood likely began modestly over thousands of years. Picture a small stream of water gradually eroding the strait's rock, increasing in size as it continued to flow. Eventually, the pressure built up to the point of explosion.

Initially, Garcia-Castellanos suspected his computer models were erroneous, leading him to seek corroborating evidence. His team discovered indications of a channel connecting the Atlantic to the Mediterranean through seismic data and rock core samples taken from a proposed train tunnel between Spain and Morocco. They identified a 390-kilometer erosion channel running east to west through the Strait of Gibraltar into the Mediterranean.

"This erosion channel varies from 2 km in width and over 200 m in depth on the Atlantic side (where it intersects the bedrock) to over 15 km in width and more than 500 m in depth in the Alborán Sea (where it erodes Miocene sediment)."

They also found multiple sites throughout the Mediterranean where significant sediment deposits suggest a massive flooding event occurred. However, what would such an event look like?

To put the scale of the Zanclean Mega Flood into perspective, Mike Sowden compares it to the power of Niagara Falls, where approximately 2,400 cubic meters of water cascade every second, equivalent to the weight of an Airbus A380. In contrast, Garcia-Castellanos’ model indicates that the peak flow of the Zanclean Flood reached an astonishing 100 million cubic meters per second—over 40,000 times the volume of water flowing at Niagara Falls.

Imagining such power is nearly incomprehensible, rendering historical battles like Salamis, the Punic Wars, and the Taranto attack as mere footnotes in comparison. This cataclysmic event likely laid the groundwork for the Mediterranean's history, creating a vast sea that would witness centuries of human endeavors—and possibly even giving rise to the Nile River.

Chapter 2: The Myth and Reality of the Mediterranean's Birth

"In his Historia Naturalis (~77 AD), Pliny the Elder recounts a legend popular among the inhabitants of southern Iberia, stating that the Mediterranean Sea was once deserted and cut off from the ocean until Hercules, with his sword, carved an inlet between Jebel-el-Mina (Africa) and Gibraltar (Europe), allowing the ocean to flow back into the Mediterranean Basin and 'changing the face of Nature.'"

— Daniel Garcia-Castellanos and associates, Earth-Science Reviews, Volume 201, 2020

Studying ancient history presents challenges. Imagine fragmenting elements of your life and passing them to a future civilization a thousand years later—could they accurately reconstruct your existence? Future researchers may draw conclusions that could be correct, but fully comprehending your life would be a daunting task.

When examining prehistoric events that occurred millions of years ago, researchers rely solely on geological indicators and fossil remains. The study of salt, gypsum, halite, and occasional marine fossils represents their only means of interpretation, underscoring the complexities of this investigation.

It is no surprise that terms like "likely," "might," and "possibly" frequently appear. This is because the events in question transpired over five million years ago, leaving much to speculation. While Garcia-Castellanos and his colleagues propose an intriguing theory supported by evidence, it remains just that—a theory.

They also note that other significant floods have occurred in history, such as the Missoula Floods in Washington State and the Altai Flood in Russia. Still, some scientists argue that the Mediterranean refilled gradually, like other geographical changes. This debate is likely to continue among scientists for years to come. Regardless, the tale of the Zanclean Mega Flood presents a captivating narrative—a fitting prologue for a region steeped in remarkable history, suggesting that a mythic Hercules may have indeed sculpted the iconic Gibraltar inlet in a monumental surge, setting the stage for an array of historical events to come.