How Ice Needles Create Spontaneous Zen Gardens
Some of the most breathtaking zen garden patterns on the planet owe their existence to an unlikely artist: thousands of tiny "ice needles."
Credit: Quan-Xing Liu of East China Normal University
Credit: Quan-Xing Liu of East China Normal University
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TechTranscript
00:00 In high latitude permafrost environments and high altitude mountains, there are a large
00:12 number of mysterious regular surface patterning, also known as patterning, such as the Qinghai-Tibet
00:19 plateau and other freezing regions in China, the Svaoban Islands in Norway in the Arctic
00:27 and the Alpine regions in Ethiopia.
00:31 The patterned ground is made up of different kinds of stones and soils, some arranged in
00:37 polygonal net, stone circles and others in strapped spatial patterns.
00:44 The origin of these regular patterns has long been puzzling scientists, but recently this
00:51 enigma is starting to be solved.
00:57 Scientists now attribute the spontaneous regular patterns to a process called spatial self-organization.
01:05 In the periglacial environment, winds gathering together with soil freezing thawing cycles
01:11 are speculated to drive the aggregation and separation movements of granular particles
01:17 in the soil, which eventually result in assorted spatial patterns of stones on the land surfaces.
01:25 This idea has been sparked by theoretical and empirical studies in physics, chemistry,
01:38 biology and ecology.
01:41 However, it is notoriously difficult to test this idea in the field.
01:46 The geomorphological systems in cold regions often evolve at extremely slow rates.
01:53 Largely forbidden human observers to record the processes.
01:58 Many existing numerical models have suggested that differential frost heave and radial expansion
02:05 of the fine-grained soils can lead to the movement of surface particles to the margins
02:11 of the plugs and the formation of the self-organized patterns.
02:16 This mechanism can reproduce a variety of large-scale assorted patterns, such as polygons
02:22 and sorted circles, but direct experimental evidence for this model is still lacking.
02:30 Scientists have long speculated that needle ice formed in the permafrost layer could play
02:35 a role.
02:36 A new research led by an international team from China, Japan, the US and the Netherlands
02:43 revisited this old idea with brand new evidence and theory.
02:49 The researchers designed an elegant experiment system that allows for the formation of needle
02:54 ice in well-controlled lab conditions.
02:58 This system can mimic a time machine with which the observers can push the fast-forward
03:03 button to speed up the process of land surface evolution within a microcosm.
03:09 Within a couple of weeks, the researchers can now observe the years or even decades
03:14 long process happening in nature.
03:18 They use video camera and computer program to automatically track the movement trajectory
03:24 of every single stone and reproduce such observed processes in computer with mathematical models.
03:31 The researchers found that driven by the freezing-thaw cycles in soils, the surface granular particles
03:37 migrated towards the stone-rich areas from stone-poor areas.
03:42 This is exactly the process where a variety of older spatial patterns of stones arises
03:48 from.
03:49 This group of scientists have replicated the experiment numerous times with all kinds of
03:55 settings of needle ice properties and stone field concentration.
04:00 They put together these nonlinear relationships between different needle ice height and stone
04:05 field concentration to demonstrate that the geomorphological pattern formation process
04:11 has the same physical principle as that underpins the water-oil separation process.
04:16 像分离原理的本质是石头由极浓度向高浓度运动。
04:22 这个运动方式与传统的扩散是不一样的。
04:27 Known as phase separation mechanism, the phase separation theory perfectly reproduced
04:32 the different types of sorted patterns and found that the activity of needle ice plays
04:37 a dominant role in shaping this pattern ground.
04:42 What makes the scientists more exciting is that their phase separation model can also
04:46 perfectly reproduce the similar sorted patterns found in the Martian boulders by curiosity.
04:53 Can this seen as another evidence reinforcing the existence of soil-water on Mars?
05:00 Does this mean freezing thawing cycles also drive the evolution of Martian landscapes?
05:06 It's still too early to answer this question, but the study does open many opportunities
05:12 to look into geological and geomorphic evolution of Earth-like planets.
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