How were mysterious boreholes on California seabed formed? Methane leak occurred 2,80,000 years ago or sinister mysteries?

Scientists were shocked when they found thousands of mysterious holes on the seabed off Slur in California in 1999. The Monterey Bay Aquarium Research Institute (MBARI) researchers found these holes when they were surveying the seafloor. They were clueless about the nature and origin of these holes spread across a vast area. There were more than 5,200 holes, situated between 1,600 and 5,200 feet below sea level. They measured about 500 feet across and around 16 feet deep. The boreholes resemble small underwater craters. What could be the source of these holes and why these were created? Did methane bubbles create these holes like pockmarks found elsewhere? The tiny bubbles of methane gas would rise from below the surface, bringing with them seafloor sediments. There was no answer to any of the questions.

Underwater avalanche

Now, 25 years after the discovery of these mysterious holes, scientists believe that these pockmarks were made by underwater avalanches carrying sediment deeper into the ocean, reports 'xatakaon.com'. The holes may have been formed by “sediment gravity flows.” MBARI found in its study that the flows occurred several times over the past 280,000 years.

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MBARI: Not created by methane

MBARI researchers Eve Lundsten and Charles Paull at the Fall Meeting of the American Geophysical Union in San Francisco said that the cause and persistence of the pockmarks remains a mystery, but there is no evidence to suggest that they were created from gas or fluid in the seafloor in the recent past. He also said that the micro-depressions are recently formed erosional features, they are not ‘incipient pockmarks.’

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FAQs:

What are small mysterious pockmarks found off Slur in California?
Scientists of the Monterey Bay Aquarium Research Institute (MBARI) found thousands of small holes on the seabed when they were surveying the seafloor. These pockmarks were spread across a vast area on the seabed off Slur in California in 1999.

How many pockmarks were found in Slur in California?
There were more than 5,200 holes, situated between 1,600 and 5,200 feet below sea level. They measured about 500 feet across and around 16 feet deep. The boreholes resemble small underwater craters.