Fracture networks in frozen ground

Plug, Lawrence J.; Werner, B. T.

doi:10.1029/2000jb900320

Cited by 49 publications

(31 citation statements)

References 42 publications

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“… Sletten et al [2003] present observations which suggest that in antarctic permafrost younger thermal‐contraction polygons begin with orthogonal trough intersections and minimal surface relief, while over time these patterns evolve into equiangular intersections and develop substantial topographic relief. Alternatively, the evolution from orthogonal to equiangular (hexagonal) networks may be related to the progressive subdivision of patterns as networks age [ Black , 1976], or to an increase in sinuosity of the primary fractures [ Plug and Werner , 2001] related to subsurface heterogeneity. In addition, the superposition of small polygons over all other features (including all small craters; see Figure 9d) suggests that they are the most recent development on this surface.…”

Section: Discussionmentioning

confidence: 99%

Periglacial landforms at the Phoenix landing site and the northern plains of Mars

Mellon¹,

Arvidson²,

Marlow³

et al. 2008

J. Geophys. Res.

125

155

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[1] We examine potentially periglacial landforms in Mars Orbiter Camera (MOC) and High Resolution Imaging Science Experiment (HiRISE) images at the Phoenix landing site and compare them with numerical models of permafrost processes to better understand the origin, nature, and history of the permafrost and the surface of the northern plains of Mars. Small-scale (3-6 m) polygonal-patterned ground is ubiquitous throughout the Phoenix landing site and northern plains. Larger-scale (20-25 m) polygonal patterns and regularly spaced (20-35 m) rubble piles (localized collections of rocks and boulders) are also common. Rubble piles were previously identified as ''basketball terrain'' in MOC images. The small polygon networks exhibit well-developed and relatively undegraded morphology, and they overlay all other landforms. Comparison of the small polygons with a numerical model shows that their size is consistent with a thermal contraction origin on current-day Mars and are likely active. In addition, the observed polygon size is consistent with a subsurface rheology of ice-cemented soil on depth scales of about 10 m. The size and morphology of the larger polygonal patterns and rubble piles indicate a past episode of polygon formation and rock sorting in thermal contraction polygons, while the ice table was about twice as deep as it is presently. The pervasive nature of small and large polygons, and the extensive sorting of surface rocks, indicates that widespread overturning of the surface layer to depths of many meters has occurred in the recent geologic past. This periglacial reworking has had a significant influence on the landscape at the Phoenix landing site and over the Martian northern plains.

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Section: Discussionmentioning

confidence: 99%

Periglacial landforms at the Phoenix landing site and the northern plains of Mars

Mellon¹,

Arvidson²,

Marlow³

et al. 2008

J. Geophys. Res.

125

155

View full text Add to dashboard Cite

show abstract

“…In contrast, cracks in patterned ground areas do not increase in depth through time, except at sites where the surface is lowered through time due ice sublimation as in central Beacon Valley. However, the periodic thermal forcing that drives the opening and closure of cracks, as well as partial healing of cracks, does provide opportunities for new cracks to form where local stresses are sufficient and old cracks to cease to be active where stresses are low [ Plug and Werner , 2001]. This can result in the regularization of polygons at the surface to form arrays of essentially equidimensional and equiangular polygons.…”

Section: Discussionmentioning

confidence: 99%

Resurfacing time of terrestrial surfaces by the formation and maturation of polygonal patterned ground

2003

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[1] To help interpret the polygonal patterned ground on Mars, we present recent findings about a similar form of patterned ground in a particularly cold and arid region on Earth, the Dry Valleys of Antarctica. In this region, distinct arrays of interconnected polygons, which we refer to herein simply as patterned ground, characterize many surfaces, reflecting a subsurface network of interconnected, subvertical wedges of sand that grow incrementally as sand progressively fills soil fractures. The fractures form initially as thermoelastic stresses arise during periods of rapid cooling of frozen ground, and they continue to open and close in response to thermal cycles. We describe the initiation and maturation of the patterned ground using data for the growth of sand wedges and for the evolution of crack patterns and microrelief over time scales ranging up to 10 6 years.

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“…Self‐organization is a general property of many nonlinear, dissipative systems. It has been hypothesized to play a significant role in braided rivers [ Murray and Paola , 1994], sand dunes [ Werner , 1995], frozen soils [ Kessler et al , 2001; Plug and Werner , 2001], large‐scale coastline development [ Ashton et al , 2001], forest fires [ Pastor et al , 1999], and insect behavior [ Theraulaz and Bonabeau , 1995]. In laboratory studies and simulations with numerical models, self‐organized dynamics become simpler, less sensitive to detail, and more easily predicted as order increases and timescales become longer.…”

Section: Discussionmentioning

confidence: 99%

Test of self‐organization in beach cusp formation

Coco

2003

J. Geophys. Res.

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[1] Field observations of swash flow patterns and morphology change are consistent with the hypothesis that beach cusps form by self-organization, wherein positive feedback between swash flow and developing morphology causes initial development of the pattern and negative feedback owing to circulation of flow within beach cusp bays causes pattern stabilization. The self-organization hypothesis is tested using measurements from three experiments on a barrier island beach in North Carolina. Beach cusps developed after the beach was smoothed by a storm and after existing beach cusps were smoothed by a bulldozer. Swash front motions were recorded on video during daylight hours, and morphology was measured by surveying at 3-4 hour intervals. Three signatures of selforganization were observed in all experiments. First, time lags between swash front motions in beach cusp bays and horns increase with increasing relief, representing the effect of morphology on flow. Second, differential erosion between bays and horns initially increases with increasing time lag, representing the effect of flow on morphology change because positive feedback causes growth of beach cusps. Third, after initial growth, differential erosion decreases with increasing time lag, representing the onset of negative feedback that stabilizes beach cusps. A numerical model based on self-organization, initialized with measured morphology and alongshore-uniform distributions of initial velocities and positions of the swash front at the beginning of a swash cycle, reproduces the measurements, except for parts of one experiment, where limited surveys and a significant low-frequency component to swash motions might have caused errors in model initialization.

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Fracture networks in frozen ground

Cited by 49 publications

References 42 publications

Periglacial landforms at the Phoenix landing site and the northern plains of Mars

Periglacial landforms at the Phoenix landing site and the northern plains of Mars

Resurfacing time of terrestrial surfaces by the formation and maturation of polygonal patterned ground

Test of self‐organization in beach cusp formation

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