Star Burst Patterns On The Ice
As I looked over the railing on the bridge that crosses the Pelican Creek Wetland along the East Entrance Road In Yellowstone National Park, I was amazed by the star shapes on the surface of the ice on some of the ponds. I had seen these fractal like patterns in ice before. As a boy in Wyoming , I remember wondering how these features form, but after years of wintering in Southern Louisiana and Southern Texas, those memories were buried deep in my onboard computer. As I recalled my boyhood observations, I was left wondering how do these features form? After a quick search of the internet, I found that these features are quite common. Henry Thoreau described such features in Walden. He spent time on the ice in winter and describes how it forms very scientifically. He did take notice of the ice stars which he describes as looking like spiderwebs. His interpretation of how they form is somewhat convoluted and does not fully explain the phenomena. Since Thoreau, several ideas and theories have been offered. In 2007, two geophysicists, Victor Tsai of Harvard University (Now of Brown University) and John Wettlaufer of Yale University, modeled the formation of these star shaped holes in the ice. They determined that the shape is governed by the properties of the snow that covers the ice. Their work suggests that the star patterns are formed when a hole in a recently frozen lake allows water to swell up from beneath and spread over the snow-covered surface, leaving dark “fingers” of melted ice that stem from a central point. Previously, some geologists, physicists and others had suspected that the fingers form if there is a warming trend after the ice forms and snow covers the ice. As the temperature increases, some ice melting occurs. The water starts to upwell and flow in one direction, causing the snow to melt faster in that region and thus helping the water to flow faster. Tsai and Wettlaufer first constructed a simple mathematical model to test this idea. They began by assuming that the rate of flow of the water is dependent on how compacted and thus how porous the snow is. The model also took into account parameters such as the driving pressure and heat content of the water and how fast heat could transfer by diffusion. They found that of these parameters, the snow porosity and maximum driving pressure governed how many fingers extended from the holes. They then built a physical laboratory experiment to test their ideas and ran it numerous times. The mathematical model did not perfectly predict the number of holes developed in the ice in the laboratory experiment but was right 94% of the time (not bad for a model). For more info, see the references below which were used to write this caption:
physicsworld.com/a/icy-stars-reveal-the-secret-of-their-p...
journals.aps.org/pre/abstract/10.1103/PhysRevE.75.066105
Star Burst Patterns On The Ice
As I looked over the railing on the bridge that crosses the Pelican Creek Wetland along the East Entrance Road In Yellowstone National Park, I was amazed by the star shapes on the surface of the ice on some of the ponds. I had seen these fractal like patterns in ice before. As a boy in Wyoming , I remember wondering how these features form, but after years of wintering in Southern Louisiana and Southern Texas, those memories were buried deep in my onboard computer. As I recalled my boyhood observations, I was left wondering how do these features form? After a quick search of the internet, I found that these features are quite common. Henry Thoreau described such features in Walden. He spent time on the ice in winter and describes how it forms very scientifically. He did take notice of the ice stars which he describes as looking like spiderwebs. His interpretation of how they form is somewhat convoluted and does not fully explain the phenomena. Since Thoreau, several ideas and theories have been offered. In 2007, two geophysicists, Victor Tsai of Harvard University (Now of Brown University) and John Wettlaufer of Yale University, modeled the formation of these star shaped holes in the ice. They determined that the shape is governed by the properties of the snow that covers the ice. Their work suggests that the star patterns are formed when a hole in a recently frozen lake allows water to swell up from beneath and spread over the snow-covered surface, leaving dark “fingers” of melted ice that stem from a central point. Previously, some geologists, physicists and others had suspected that the fingers form if there is a warming trend after the ice forms and snow covers the ice. As the temperature increases, some ice melting occurs. The water starts to upwell and flow in one direction, causing the snow to melt faster in that region and thus helping the water to flow faster. Tsai and Wettlaufer first constructed a simple mathematical model to test this idea. They began by assuming that the rate of flow of the water is dependent on how compacted and thus how porous the snow is. The model also took into account parameters such as the driving pressure and heat content of the water and how fast heat could transfer by diffusion. They found that of these parameters, the snow porosity and maximum driving pressure governed how many fingers extended from the holes. They then built a physical laboratory experiment to test their ideas and ran it numerous times. The mathematical model did not perfectly predict the number of holes developed in the ice in the laboratory experiment but was right 94% of the time (not bad for a model). For more info, see the references below which were used to write this caption:
physicsworld.com/a/icy-stars-reveal-the-secret-of-their-p...
journals.aps.org/pre/abstract/10.1103/PhysRevE.75.066105