This photo shows a mudboil that has developed a raised rim after excavation of its carapace. See image 0220 for a further discussion of this phenomenon, which is related to hydrostatic pressure developed below the rigid carapace. The knife is 25 cm long. In this example, the stable mudboil has developed a weak soil profile similar to that shown in image 0221. Note the shrubby nature of the vegetation rim that surrounds this mudboil in contrast to the grassy rims evident in images 0220 and 0221. See also the process description under 0240 .