Depending on the granularity, this powder can have an abrasive feel, similar to pumice powder, and has a low density as a result of its high porosity. The typical chemical composition of oven-dried diatomaceous earth is 80 to 90% silica, with 2 to 4% alumina (attributed mostly to clay minerals) and 0.5 to 2% iron oxide. Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae.
A Pacinian corpuscle is a type of touch receptor located in the skin. It is classed as a mechanoreceptor, meaning it is part of the group of sensory receptors that respond to touch and pressure.lthough there are similarities between the two, a Pacinian corpuscle is not as discriminatory as the type of fine-touch mechanoreceptor present in the fingertips, known as Meissner's corpuscle. This type of sensory receptor lies closer to the surface of the skin and adapts only moderately fast.
A Dictionary of Earth Sciences | 1999 | 588 words. Â© A Dictionary of Earth Sciences 1999, originally published by Oxford University Press 1999. Plinian eruption An explosive volcanic eruption of pyroclastic ejecta forming an eruption column which may be up to 55 km high, dispersing ejecta over an area of 500â5000 km.The eruption column has the distinctive, spreading, branched shape of the stone pine (Pinus pinea) native to the Mediterranean region. Plinian eruption may produce thick, airfall, pumice deposits, or the eruption column may collapse to generate a pyroclastic flow. This type of eruption is named after Pliny the elder, who died at Pompeii in AD79 during the eruption of Vesuvius that destroyed the city.