#gravity-driven flow

[fuckyeahfluiddynamics]

Sewage systems rely on gravity to remove waste from our homes and carry it toward treatment plants. But that constant downward slope can't always be maintained. Sometimes we have to bring the sewage back up to the surface to process it. (Image and video credit: Practical Engineering)

[fuckyeahfluiddynamics]

To the naked eye, glaciers don’t appear to move much, but appearances can be deceiving. Like avalanches and turbidity currents, glaciers flow under the influence of gravity. They typically move at speeds around 1 meter per day, but some glaciers, like those shown above in Pakistan’s Central Karakorum National Park, can briefly surge to speeds a thousand times higher than their usual. The animation above shows 25 years worth of Landsat satellite imagery, enabling one to more easily observe the motion of these slow giants. Try picking out a feature along one of the glaciers and watch it move year-by-year. The glaciers just right of the image centerline are some of the best!  (Image credit: J. Allen; via NASA Earth Observatory; submitted by Vince D)

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[fuckyeahfluiddynamics]

Humans often trigger avalanches purposefully before natural ones can occur. Either way, avalanches begin when external stresses on the snow pack exceed the strength within the snow pack or at the contact between the snow and the ground. Acceleration of the snow is gravity-driven. If the snow mixes with air, powder clouds can form that carry snow even further than the main slab. Although the snow itself is not a fluid, once an avalanche gets moving, its behavior can be better modeled as a fluid than as a solid.

[fuckyeahfluiddynamics]

Landslides, despite their inclusion of solid materials, function essentially as gravity-driven fluid flows. This timelapse video shows a recent earthflow in Wyoming near the Snake River. Rapid snowmelt and heavy rainfall combined to cause a seven day landslide over the highway and into the river. # (via Bad Astronomy)