Unveiling Marmara’s hidden past: Did tsunamis strike Istanbul?
The keel of a shipwreck uncovered during the Yenikapi metro construction is seen at the excavation site, shrouded in mist. (Photo via Yenikapi Excavations)
The “Marmaray” project, designed to connect both sides of the Bosphorus via a rail tunnel, led to extensive archaeological excavations in Yenikapi under the supervision of the Istanbul Archaeological Museums.
These excavations, which lasted nearly ten years, revealed groundbreaking discoveries, including evidence that ancient tsunamis may have struck Istanbul. The most significant find was the unearthing of the Late Roman (Byzantine) period harbor, known as Theodosius Harbor.
During the excavations at the site designated for the construction of metro and Marmaray stations, 37 shipwrecks were identified.
This discovery represents the world’s largest known collection of shipwrecks found in a single excavation area, offering an unprecedented glimpse into ancient maritime history.
Theodosius Harbor: A key trade hub of the Byzantine Empire
Theodosius Harbor played a vital role in the grain trade during the Byzantine period. Ships from Alexandria would dock here, unloading their cargo of grain for distribution throughout Constantinople.
The discovery of ships used for trade, alongside Byzantine naval galleys, marks a first in the history of archaeology.
Geoarchaeological studies in the harbor area suggest that sediment layers, particularly “Unit 4,” were formed by tsunamis triggered by the earthquakes of 554 A.D. and 557 A.D.
Earthquakes in Marmara region throughout history
The Marmara region has experienced numerous devastating earthquakes throughout history. Over the past 2,000 years, Istanbul alone has suffered at least 34 earthquakes of magnitude 7.0 or higher. The earliest recorded earthquake occurred in A.D. 29, while the first detailed account dates to February 1, 363 A.D.
Byzantine sources document extensive destruction caused by the 1265 earthquake, including tsunamis.
Historical records confirm that tsunami waves left deposits on land. While most tsunamis in the Marmara Sea are relatively small, some have produced waves reaching 6 to 10 meters in height.
During the mid-6th century, Constantinople experienced three major earthquakes in quick succession—August 542 A.D., August 554 A.D., and December 557 A.D.
The Byzantine historian Agathias, an eyewitness to the 557 A.D. earthquake, described the disaster: “At midnight, while all the people lay peacefully in their beds, disaster struck suddenly, shaking every building from its foundation… many lives were lost.” The destruction affected homes, churches, and baths, and once again damaged the city walls. Cracks formed in the dome of the Hagia Sophia, which eventually collapsed in 558 A.D., possibly due to an aftershock or another earthquake. Emperor Justinian ordered the architect Isidore the Younger to oversee the reconstruction, reinforcing the dome with lighter materials and raising it to its present height.
Archaeological findings at the Yenikapi (Theodosius) Harbor excavation site suggest that a debris layer may have been caused by the tsunami following the 557 earthquake.
Storm or tsunami? The debate surrounding shipwrecks in Marmara Sea
The remains of over 25 ships from the Byzantine period (10th–11th centuries A.D.) were initially thought to have sunk due to a violent storm affecting Istanbul’s coastline. However, archaeologist Metin Gokcay challenges this conclusion in his book Urban Archaeology and Istanbul.
He argues that if a storm had caused the shipwrecks, the vessels would have capsized or been severely damaged. Instead, the excavated ships were found resting intact on their keels.
One key piece of evidence is the discovery of intact cherry pits inside a basket within the wreck of Ship 12 at Yenikapi. Gokcay asserts that if a storm had sunk the vessel, neither the ship’s hull nor the cherry pits would have remained undisturbed.
Similar shipwreck patterns have been observed in tsunami events worldwide, where ships initially float before settling intact on the seabed as the tsunami recedes.
Through extensive field research, Gokcay identified three distinct tsunami layers in the excavation site. Although two of these findings were not widely accepted, one sediment layer was indisputable. This layer, found deep within the harbor, consists of a band of deposits containing stones, ceramics, bones, and soil pulled from the land by a tsunami.
The Yenikapi excavations have provided the first concrete evidence of historical tsunamis in Istanbul. These findings challenge the common belief that tsunamis do not occur in the Marmara Sea, proving that such events have shaped the region’s history and landscape.
