Coal forms from the accumulation of plant debris, usually in a swamp environment. When plant debris dies and falls into the swamp the standing water of the swamp protects it from decay. Swamp waters are usually deficient in oxygen, which would react with the plant debris and cause it to decay.
Porokeratosis is generally considered to be a benign condition though malignant transformation has been seen in all but the punctate variety, necessitating regular followup of patients with porokeratosis (Maubec et al., 2005; Sasson & Krain, 1996).
Not really. It was originally a clay (sedimentary rock) which became a shale through intens compaction (most often because of burial) which became a slate (metamorphic rock) t â¦ hrough low-grade regional metamorphism. In general, compaction and low-grade regional metamorphism reduces porosity, so it is not really porous.