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).
7. A/An __________ is a benign skin growth that has a waxy or pasted-on look that can vary in color from light tan to black and occur most commonly in the elderly. seborrheic keratosis. 8. Excessive sweating in one area or over the whole body is known as __________.