Because they form by leakage of methane into seawater it implies that something at that time caused a large release of methane into the ocean. (sciencedaily.com)
The rapid release of methane gas in a closed system can result in a rapid increase in pressure. (en.wikipedia.org)
The accelerated release of methane is one of the so - called «tipping point» concerns related to climate change. (treehugger.com)