An Under Water River?

[Panther_99FS]

http://petapixel.com/2013/08/27/mesmerizing-photos-of-cenote-angelita-an-underwater-river/ :mixedsmi:

 

[AndyG43]

That is pretty damn cool!

Best we can manage in London is an Over Railway River!!

View attachment 92486

The River Westbourne, part of which runs over Sloane Square Tube Station. It's fun watching tourists trying to work out where the sounds of running water are coming from.

 

[Sascha66]

That is very strange ... but also strangely memorable ... Nature is wonderful! Very interesting set of images too!

 

[ThinkingManNeil]

Those are some amazing images. Nature never fails to amaze or surprise. Here's some amazing video I came across a few years back of an active molten sulfur pond on the submarine volcano Daikoku off of the northern Marianas island arc at a depth of some 1,500m...

N.

 

[stiz]

underwater stuff fascinates me, it seems everytime someone goes down they find something new, i've long belived we should spend NASAs buget on exploring the ocean rather than space

 

[Skyhawk_310R]

To piggyback on this situation, here is something that has caused mass human death in the past, and might do so again. There are lakes where it is true that a layer of gas remains trapped at depth due to the pressure of the water layer above it reaching sufficient force to keep the gas level as an underwater dome, similar to what happens when gas remains trapped by the pressure of ground. Yet due to relatively minor oscillations, that gas can spontaneously boil into suspended state and boil up to the surface and gather in an heavier-than-air mass that can float into a nearby village and kill the people due to displacement of air. I cannot immediately recall where it happened, but a relatively minor seismic event caused the displacement of the pressure balance -- essentially the equivalent of a brief shake of a soda bottle except that would cause gas in suspension to form nuclear attachments and boil up. In this case, the gas was kept trapped by a pressure force on top and the destabilization caused the gas to exert its rising forces.

Ken

 

[Naismith]

That is pretty damn cool!

Best we can manage in London is an Over Railway River!!

View attachment 92486

The River Westbourne, part of which runs over Sloane Square Tube Station. It's fun watching tourists trying to work out where the sounds of running water are coming from.

Interesting factoid - in 1730 Queen Caroline of Anspach and the wife of King George II ordered the River Westbourne be diverted in order that it run through Hyde Park and form the Serpentine Lake which was the world first artificially created natural looking lake.

 

[ThinkingManNeil]

To piggyback on this situation, here is something that has caused mass human death in the past, and might do so again. There are lakes where it is true that a layer of gas remains trapped at depth due to the pressure of the water layer above it reaching sufficient force to keep the gas level as an underwater dome, similar to what happens when gas remains trapped by the pressure of ground. Yet due to relatively minor oscillations, that gas can spontaneously boil into suspended state and boil up to the surface and gather in an heavier-than-air mass that can float into a nearby village and kill the people due to displacement of air. I cannot immediately recall where it happened, but a relatively minor seismic event caused the displacement of the pressure balance -- essentially the equivalent of a brief shake of a soda bottle except that would cause gas in suspension to form nuclear attachments and boil up. In this case, the gas was kept trapped by a pressure force on top and the destabilization caused the gas to exert its rising forces.

Ken

Yup. That happened at Lake Nyos in Cameroon, back in August of 1986. Nyos is a volcanic crater lake that had a considerable amount of CO2 trapped in a stratified water column, and it's thought that a run-out landslide from somewhere on the caldera wall plunging into the lake destabilized the layers and triggered what's called a limnic eruption of the trapped gas.

Lake Kivu in the western branch of the Great Rift Valley in central Africa is another one they worry about. The city of Goma, pop. ~1M, is situated on shore and both aren't far from two major volcanoes - Nyiragongo and Nyamuragira. Nyamuragira is frequently active, but it's Nyiragongo that's the very real threat. It produces large volumes of very fluid basalt lava - some of the most fluid and fastest moving lava on Earth - and just the immense hydraulic pressure of huge quantities of this lava in the volcanoes system often causes fissures to open up downslope (as happened in the 2002 eruption just outside Goma which buried much of the town and part of the airport under lava. Several people died). Kivu contains a mix of both methane and CO2 and the fear is that a large lava flow from Nyiragongo, a fissure on its slopes, or a fissure beneath the lake itself could destabilize the gas and cause a limnic eruption...

N.

 

[ThinkingManNeil]

This is, what I think, one of the most amazing images from Nyiragongo. It's the cast of a body of an elephant that got caught by a very fast moving lava flow from Nyiragongo during an eruption back in 1977. The elephant's bones are clearly visible in the cast, as is the general outline and shape of the head and the body, but if you look carefully at the upper left hand corner of the pic, you can also just make out the outline of the elephant's trunk...

View attachment 92556

Elephants weren't the only casualties. Some seventy people died when the flow, which was clocked at moving as fast as 60 mph on the volcano's upper slopes, swept across a road that was full of locals heading to a farmer's market.

N.

 

[Skyhawk_310R]

Yup. That happened at Lake Nyos in Cameroon, back in August of 1986. Nyos is a volcanic crater lake that had a considerable amount of CO2 trapped in a stratified water column, and it's thought that a run-out landslide from somewhere on the caldera wall plunging into the lake destabilized the layers and triggered what's called a limnic eruption of the trapped gas.

Lake Kivu in the western branch of the Great Rift Valley in central Africa is another one they worry about. The city of Goma, pop. ~1M, is situated on shore and both aren't far from two major volcanoes - Nyiragongo and Nyamuragira. Nyamuragira is frequently active, but it's Nyiragongo that's the very real threat. It produces large volumes of very fluid basalt lava - some of the most fluid and fastest moving lava on Earth - and just the immense hydraulic pressure of huge quantities of this lava in the volcanoes system often causes fissures to open up downslope (as happened in the 2002 eruption just outside Goma which buried much of the town and part of the airport under lava. Several people died). Kivu contains a mix of both methane and CO2 and the fear is that a large lava flow from Nyiragongo, a fissure on its slopes, or a fissure beneath the lake itself could destabilize the gas and cause a limnic eruption...

N.

I figured one of our very bright members would fill in the gaps in my memory.

Cheers,

Ken