In yesterday's post I wrote about the possibility that Nahuelito (Lake Nahuel Huapi's cryptid) was actually an eruption of natural gas bubbles on the lake's surface.
I was brushing up on this subject and rereading some old sightings and I have become more and more convinced that this is an excellent explanation. Please let me share my research with you:
The following are only three sightings that mention bubbles and foam together with Nahuelito, I quote them below and highlight the relevant parts:
- Date: 30.01.1988. “this alleged animal has a dark back and around it, it lets off a strange boiling of about 10 or 15 meters (30 - 45 ft.) diameter”. 
- Date: 04.01.1998. Graciela Carello and Rubén Ehara saw at Ragintuco Creek, at the mouth of Huemul Fjord, while fishing: “that the water is sucked in, as if announcing that something will surge. Then, all the surface filled up with a white foam and the back [of an animal] began to surface, of a dark brown color”.
- Date: 29.04.2008. “a man saw something like two 'bus roofs' or two rectangular submarines that emerged producing an important quantity of bubbles […] Both shone intensely under the sunlight”.
This last sighting is shown in the following photograph:
Common elements in each sighting: bubbles and foam.
Explaining the phenomena in a clear and detailed manner
Along the fault (A), oozes oil and natural gas (mostly methane) and are captured in a "fault trap" which accumulates the gas (B) and the oil(C).
The overlying water's pressure does not let the oil or gas escape. As the lake is over 450 m deep (1,475 ft), the column of water applies a pressure of 45 atm. (approx. 45 bar) to the gas. To escape it must overcome this pressure.
The gas builds up until its pressure is greater than 45 bar, and escapes.
It is possible that methane hydrates may form  (the frozen water molecules form a lattice that traps the methane within it). This can happen under certain conditions of high pressure and low temperature which can be found on Nahuel Huapi's bed. Hydrates are even found in some deep lakes such as Baikal in Siberia and perhaps Lake Superior in the U.S.
The gas, upon reaching the adequate pressure, suddenly escapes through the rocsk of the lake's bed(i) as a large bubble (d) dragging small ammounts of oil (E), towards the surface (F) where it surges generating froth, foam and bubbles (G) and a spill of dispersed hydrocarbons (H). These oil residues could account for the dark "animal backs" seen in the foam as mentioned by Carrello and Ehara.
The incicent could create a wake as the foam is dragged away by the waves it produces, as can be seen in the next photograph, taken from a video :
Modelos that have simulated this phenomenon with the use of computers  indicate that the bubble does not have to be a spherical ball. It can have the shape of a lens, with a flat bottom face while its upper surface is dome shaped. When it reaches the surface it deforms it into a convex shape and bursts shooting a jet of high speed water that falls inwards, towards the hollow bubble, this could sink and drag under any boat that sailed over it.
Comments and discussion
It is interesting that the dome was mentioned in the first sighting of Nahuelito around 1910, but it was only made public in 1922, coincidentally with the plesiosaur expedition.
The article was published in the Toronto Globe, Canada, April 6, 1922 under the headline “Local man lays claim to having caught sight of gigantic plesiosaur”. The man, named George Garret, said that about 1910 as a manager of company on Lake Nahuel Huapi while sailing in “an inlet called Pass Coytrue” (Paso Coihue on the Huemul Fjord), he saw:
an object which appeared to be 15 or 20 feet [4.5 or 6 m] in diameter, and perhaps six feet above the water [1.8 m]. After a few minutes, the monster disappeared. […] .
It was a circular object that protruded above the water like a dome.
These enormous bubbles can also produce bizarre sounds which have been heard in different parts around the world from Holland, Canada, Italy to Bangladesh, and they are known as mistpouffers.
The gas could also escape forming a large amount of small bubbles instead of one large one. This can be seen in the following image:
This is gas escaping at a lake in Alaska, but it is not methane from an oil field but degassing from methane hydrates. The lake is shallow (roughly 2m - 6.5 ft.) so no great volumes of gas can accumulate there.
This smaller bubbles outburst could also sink ships because the water with methane bubbles would have a lower density than usual (1 g/cm3). Even a person with a life jacket would sink like a stone is this less denser water.
 Anónimo, Volvió a aparecer el monstruo del lago Nahuel Huapi: muchos testigos. Clarín, Buenos Aires. 02.02. 1988.
 Diario Hoy, (1998). Volvió a aparecer “Nahuelito” en Bariloche. La Plata, Argentina. 11.01.1998
 Bariloche 2000 Diario Digital, (2008). Uno ya era bastante. Bariloche, Argentina. 30.04.2008. http://www.bariloche2000.com/archivo/la-ciudad/30100.html
 Anna Salleh (2003). Giant bubbles could sink ships, say maths experts. ABC Science. 24.10.2003
 Coleman, L. y Huyghe, P., (2003). The Field Guide to Lake Monsters, Sea Serpents and Other Mystery Denizens of the Deep. New York: Jeremy P. Tarcher/Putnam. pp.120+
 Carolyn Ruppel, John Pohlman, and Charles Worley, (2009). Studying the Link Between Arctic Methane Seeps and Degassing Methane Hydrates U.S.G.S., Sound Waves. Oct. 2009.
 Departrment of Energy. Necessary Conditions for Methane Hydrate Formation
 Signato F. Nahuelito, Bariloche, Buenos Muchachos, Año 93.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia2010 International Year of Biodiversity Copyright 2009-2010 by Austin Whittall ©