The circles appeared after a storm last week , " Gervase said . It 's likely a more mundane explanation , one expert says . Scientists believe warm water from the bottom of the lake is likely the cause . Some believe that birds , fish or aliens were responsible .
The circles appeared after a storm last week , " Gervase said . Scientists believe warm water from the bottom of the lake is likely the cause . Some believe that birds , fish or aliens were responsible .