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Dissolved gas in liquid is able to power violent eruptions. Two kinds of such gas-driven eruptions are known in nature: explosive volcanic eruptions driven by dissolved H2O in magma at high temperatures and lake eruptions driven by dissolved CO2 in water at low temperatures. There are two known occurrences of lake eruptions, one in 1984 (Lake Monoun) and one in 1986 (Lake Nyos), both in Cameroon, Africa. The erupted CO2 gas asphyxiated ∼1700 people in the Lake Nyos eruption and 37 people at Lake Monoun. Here we review experimental simulations of CO2-driven water eruptions and dynamic models of such eruptions, and a bubble plume theory is applied to the dynamics of lake eruptions. Field evidence, experimental results, and theoretical models show that lake eruptions can be violent, and theoretical calculations are consistent with the high exit velocities and eruption columns inferred from observations. Furthermore, the dynamics of lake degassing experiments are consistent with theoretical models. Other kinds of gas-driven eruptions are possible and may have occurred in nature in the past. A concentrated and large release of methane gas or hydrate from marine sediment may result in an ocean eruption. Furthermore, injection of liquid CO2 into oceans might also lead to ocean eruptions if care is not taken. The various kinetic and dynamic processes involved are examined and quantified.
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Supplemental Video 1: The movie was taken at 4000 frames per second using a high-speed movie camera, and digitized and played back at 30 frames per second. Hence, the playback is a slow motion of the experiment by a factor of 133 (4 frames is equivalent to 1 ms, or 1 second is played back in 2 minutes and 13 seconds). A close-up view of the eruption front is pictured. The whole height of the view is 26 mm (the test cell length is 152 mm). Initial test cell pressure was 5 bar, and tank pressure was 0.11 bar. A polymer was added so that the viscosity is 18 times that of water (18 millipascal-second). Before the eruption, the top half of the view is CO2 gas, and the lower half is CO2-saturated water with dissolved polymer. When the diaphragm (not in the view) is ruptured, you first see the darkening of the top half. The eruption front (liquid-gas interface) oscillates at the beginning of the experiment due to shock wave reflection. Only in such close-up views, are individual bubbles clearly distinguishable. Almost all bubbles appear at the same time. That is, bubble nucleation is "instantaneous", lasting only ∼1 ms. Very few bubbles form before or after this event. This is confirmed by the similar size of the bubbles. Bubble growth data were obtained from such experiments. Even though there is a rapid vertical flow, bubbles are not stretched vertically. A foam forms and is stable. You might think you see bubbles inside bubbles. These are actually bubbles behind bubbles. Bubbles near the center (i.e., bubbles that are behind the near-wall bubbles) rise more rapidly than bubbles near the wall. Near the end of the film, there is some coalescence.
A foam is defined as a bubbly liquid in which the bubbles occupy more than 74% of the volume (i.e., the vesicularity is greater than 74%). In a foam, the liquid is the continuous phase and the gas is not, even though gas bubbles account for most of the volume. Greater than this vesicularity, spherical bubbles have to deform into polygonal surfaces in order not to break. The deformation of spherical bubbles to polyhedral bubbles accounts for the honeycomb appearance of the foam.
Zhang Y, Sturtevant B, Stolper EM. 1997. Dynamics of gas-driven eruptions: experimental simulations using CO2-H2O-polymer system. J. Geophys. Res. 102:3077–96. The original videotape with copyright was deposited to American Geophysical Union. Reproduced/modified by permission of American Geophysical Union. Download video file (MOV)
Supplemental Video 2: The movie shows the close-up view of the eruption front in slow motion by a factor of 133. A polymer was added but the viscosity is only 5 times that of water (5 millipascal-second). Initial test cell pressure was 5.2 bar, and tank pressure was 0.07 bar. There was a foam layer on top of the liquid column before the experiment. Because of the bubbly layer, the eruption starts very violently. Individual bubbles can be seen clearly and bubble growth data were obtained. Bubbles are spherical and not stretched vertically. A foam forms but is not very stable.
Zhang Y, Sturtevant B, Stolper EM. 1997. Dynamics of gas-driven eruptions: experimental simulations using CO2-H2O-polymer system. J. Geophys. Res. 102:3077–96. The original videotape with copyright was deposited to American Geophysical Union. Reproduced/modified by permission of American Geophysical Union. Download video file (MOV)