New Insights Unravel the Mystery of Ocean Floor Holes

Off the shores of Big Sur, California, lies an enigmatic underwater terrain adorned with sizable voids amidst clay, silt, and sand.

After decades of speculation, scientists from the Monterey Bay Aquarium Research Institute (MBARI) and Stanford University believe they’ve unraveled the mystery behind the peculiar circular patterns in the seabed.

Traditionally, these formations were attributed to the release of methane gas or heated fluids from the Earth’s depths, displacing sediments. However, recent findings challenge this notion, revealing discrepancies across various locations.

The Sur Pockmark Field, situated off California’s coast, stands as North America’s largest, spanning an area comparable to Los Angeles and featuring over 5,200 hollows, with an average diameter of 175 meters (574 feet) and depth of 5 meters (16 feet). While plans for an offshore wind farm loom, concerns about methane presence linger, potentially jeopardizing infrastructure stability.

During a recent expedition, MBARI’s underwater robot detected minimal signs of methane vents or fluid flows within the Sur pockmarks, prompting a reconsideration of their origin. Instead, researchers posit that gravity likely played a pivotal role.

Positioned on a continental slope, sediment samples retrieved by the robot indicate a history of intermittent downhill flows spanning back 280,000 years, with a significant event occurring around 14,000 years ago, possibly due to seismic activity or slope collapse.

The erosion caused by such events could explain the formation of pockmarks, with sediment flows widening them and even shifting the positions of neighboring formations, possibly giving rise to their ‘chain’ appearance.

“We’ve amassed a wealth of data, revealing an unexpected connection between pockmarks and sediment gravity flows,” notes MBARI research technician Eve Lundsten. “While the exact mechanisms behind their formation remain elusive, our advanced underwater technology has shed light on their persistence for hundreds of millennia.”

Despite being one of the most extensively studied seafloors along the North American west coast, much about the Sur Pockmark Field remains a mystery, including the dynamics of sediment and fluid movement.

The exploration of the ocean floor, often likened to Earth’s final frontier, is not merely driven by scientific intrigue but also by the potential for new industries like offshore wind farming and seafloor mining. However, understanding this ecosystem proves to be a daunting challenge.

“Expanding renewable energy is vital for combating climate change,” emphasizes MBARI President and CEO Chris Scholin. “Yet, there’s still much to learn about the environmental implications of offshore wind energy. Our research is part of a broader effort to decipher the mysteries of our ocean, informing decisions about marine resource utilization.”