Both options feature lens-mounted zoom toggles, pop-up flashes and dedicated video capture buttons, but only the P520 offers a dedicated mode dial, and if you're planning to make changes on the fly, that's really a necessity.

ENGADGET: Hands-on with Nikon's Coolpix P520 and L820 superzooms at CP+ (video)

But I think the reason is that you have to be rather dedicated to spot it because these plumes are only perhaps 50m to 100m across.

BBC: Methane seeps from Arctic sea-bed