Turbidity currents are underwater flows of sediments (muds, silts, sands) that begin as a slope fails. You’ve seen an analog in the eruption of Mt. St. Helens, when the side of the mountain failed and the turbulent pyroclastic flow cascaded down the volcano’s flank. Eventually, the turbulence ceases under gravity’s pull and friction with the surface over which the flow runs. The sediments (or ash in the case of the volcano) settle in a fan-shaped deposit with the larger particles (boulders) closer to the base of the slope and the progressively smaller particles (clasts) farther away where they make the edge of the “fan.” If you’ve flown over Nevada, you have seen from the air similar fan-shaped deposit called alluvial fans—though they originate from erosion mostly, rather than from catastrophic slope failure.
Turbidity currents have triggers. One is the movement of denser water into less dense water, a process Forel observed in the nineteenth century as Rhone water entered Lake Geneva. In 1929 the Grand Banks Earthquake triggered a turbidity flow that broke transatlantic undersea cables in sequence, those breaks giving researchers an idea of the flows speed and extent (60 mph and 400 mi). Slope failure caused by an overloading of sediments on an inclined surface is yet another kind of trigger. And turbidity currents have occurred almost everywhere on the planet as tectonic plate movements have created a bathymetry (undersea topography) for them. A half billion years ago a series of turbidity flows in what is now C anada’s Yoho National Park in British Columbia. The turbidites of those flows buried animals of the Cambrian Period’s “explosion” of life-forms. Their forms and lifestyles preserved by rapid burials, the Burgess Shale fossils give us a look at what life looked like before turbidity flows overwhelmed and destroyed it.
And so, as I always do, I look for a human analog.
Because the future is hidden until it becomes the present, we only rarely know what today’s actions will engender, much like that proverbial butterfly flapping its wings in the Amazon Basin causing a tornado on the Great Plains. We can through the efforts of historians sifting through the debris of the human past discover part of a way of life that some turbulent events destroyed, the burial sediments serving as the base for an ensuing but different mix of life. We don’t have prognosticators or soothsayers upon whom we can rely for a look into what is to come.
Take a seemingly innocent butterfly wing flap called E=mc^2 that triggered the bombings of Hiroshima and Nagasaki; those blasts changed the relationships among adversarial nations and changed a previous non-nuclear way of life with a threat of nuclear annihilation anywhere and anytime. You don’t live the same way as people did prior to those atomic attacks that wiped out general security just as the turbidity flows wiped out life now found fossilized in the Burgess Shale. We live on the turbidites of those nuclear bombs, with some, like the residents of those Japanese cities, closer to the point where a previous way of life collapsed, the effects of them larger and more proximal, like the boulders in turbidite deposits, whereas the rest of the world lies on the edge of the fan, aware, but not intensely so because of their distal location, that in a moment a cascade of debris can destroy everything in its path.
In a human analog, there’s another kind of turbulent flow, one that buries ways of thinking under a cascade of popular movements or insidious propaganda.
Should I be specific? I know you want me to be so, however, I prefer to ask you to look around. Life and ways of life are always on a slope with a potential for failure. Turbulence and turbidity flows interrupt the calm, with the triggers the slides unaware of inescapable consequences. The animals in the Burgess Shale—a turbidity mud deposit once underwater but now raised tectonically to the Canadian Rockies—could not have known that the Earth today is different from the Earth they knew.
Okay, since you asked, let me offer a few generalities: Media, political parties, groups, bureaucracies, religious leaders, and even individuals with an agenda initiate the self-propagating slides that like avalanches of snow are unstoppable and that result in burial of all in their paths. And when the accumulations of Big Government sit at the tops of slopes, the inevitable slide awaits the trigger that usually comes when political parties acquire unchallenged dominance. Just note that once a slide begins, nothing save friction and gravity can stop it. Think cascades of governmental regulations under which so much of free society lies buried and on which current society resides. Think of the world prior to Buddhism, Confucianism, Christianity, Islam, all of which covered vast swaths as they flowed over the human landscape. Think also, that like the turbidites that lie at the bases of continental slopes, those religions were not the products of single events, but rather of multiple events of varying intensities and masses. And like the turbidity flow of the Grand Banks earthquake, all the aforementioned flows cut the communication cables that had been laid down by a previous generation.
Not much to advise here. Simply this. Ask yourself where you are relative to a slope. Are you part of an accumulating pile of sediments at the top of a slope that will yield to a trgger event? Are you lying at the base of the slope looking at a mass with a potential to bury you as the slope fails? Or are you in the midst of a turbulent flow that is distributing downslope particles of varying sizes, the larger ones settling out first and the smaller ones settling out far from the site of disturbance? Finally, ask whether or not in this last case that the turbulent flow in which you find yourself is, in fact, a single event or instead a merging of multiple flows caused by several trigger events.
Note: Image from Conte, Thompson, Moses. Earth Science: An Integrated Perspective. William C. Brown Publishers. 1997, p. 358. The turbidity deposit is shown in yellow as a "sedimentary fan deposit."
Turbidity currents have triggers. One is the movement of denser water into less dense water, a process Forel observed in the nineteenth century as Rhone water entered Lake Geneva. In 1929 the Grand Banks Earthquake triggered a turbidity flow that broke transatlantic undersea cables in sequence, those breaks giving researchers an idea of the flows speed and extent (60 mph and 400 mi). Slope failure caused by an overloading of sediments on an inclined surface is yet another kind of trigger. And turbidity currents have occurred almost everywhere on the planet as tectonic plate movements have created a bathymetry (undersea topography) for them. A half billion years ago a series of turbidity flows in what is now C anada’s Yoho National Park in British Columbia. The turbidites of those flows buried animals of the Cambrian Period’s “explosion” of life-forms. Their forms and lifestyles preserved by rapid burials, the Burgess Shale fossils give us a look at what life looked like before turbidity flows overwhelmed and destroyed it.
And so, as I always do, I look for a human analog.
Because the future is hidden until it becomes the present, we only rarely know what today’s actions will engender, much like that proverbial butterfly flapping its wings in the Amazon Basin causing a tornado on the Great Plains. We can through the efforts of historians sifting through the debris of the human past discover part of a way of life that some turbulent events destroyed, the burial sediments serving as the base for an ensuing but different mix of life. We don’t have prognosticators or soothsayers upon whom we can rely for a look into what is to come.
Take a seemingly innocent butterfly wing flap called E=mc^2 that triggered the bombings of Hiroshima and Nagasaki; those blasts changed the relationships among adversarial nations and changed a previous non-nuclear way of life with a threat of nuclear annihilation anywhere and anytime. You don’t live the same way as people did prior to those atomic attacks that wiped out general security just as the turbidity flows wiped out life now found fossilized in the Burgess Shale. We live on the turbidites of those nuclear bombs, with some, like the residents of those Japanese cities, closer to the point where a previous way of life collapsed, the effects of them larger and more proximal, like the boulders in turbidite deposits, whereas the rest of the world lies on the edge of the fan, aware, but not intensely so because of their distal location, that in a moment a cascade of debris can destroy everything in its path.
In a human analog, there’s another kind of turbulent flow, one that buries ways of thinking under a cascade of popular movements or insidious propaganda.
Should I be specific? I know you want me to be so, however, I prefer to ask you to look around. Life and ways of life are always on a slope with a potential for failure. Turbulence and turbidity flows interrupt the calm, with the triggers the slides unaware of inescapable consequences. The animals in the Burgess Shale—a turbidity mud deposit once underwater but now raised tectonically to the Canadian Rockies—could not have known that the Earth today is different from the Earth they knew.
Okay, since you asked, let me offer a few generalities: Media, political parties, groups, bureaucracies, religious leaders, and even individuals with an agenda initiate the self-propagating slides that like avalanches of snow are unstoppable and that result in burial of all in their paths. And when the accumulations of Big Government sit at the tops of slopes, the inevitable slide awaits the trigger that usually comes when political parties acquire unchallenged dominance. Just note that once a slide begins, nothing save friction and gravity can stop it. Think cascades of governmental regulations under which so much of free society lies buried and on which current society resides. Think of the world prior to Buddhism, Confucianism, Christianity, Islam, all of which covered vast swaths as they flowed over the human landscape. Think also, that like the turbidites that lie at the bases of continental slopes, those religions were not the products of single events, but rather of multiple events of varying intensities and masses. And like the turbidity flow of the Grand Banks earthquake, all the aforementioned flows cut the communication cables that had been laid down by a previous generation.
Not much to advise here. Simply this. Ask yourself where you are relative to a slope. Are you part of an accumulating pile of sediments at the top of a slope that will yield to a trgger event? Are you lying at the base of the slope looking at a mass with a potential to bury you as the slope fails? Or are you in the midst of a turbulent flow that is distributing downslope particles of varying sizes, the larger ones settling out first and the smaller ones settling out far from the site of disturbance? Finally, ask whether or not in this last case that the turbulent flow in which you find yourself is, in fact, a single event or instead a merging of multiple flows caused by several trigger events.
Note: Image from Conte, Thompson, Moses. Earth Science: An Integrated Perspective. William C. Brown Publishers. 1997, p. 358. The turbidity deposit is shown in yellow as a "sedimentary fan deposit."
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