Word: silica
(lookup in dictionary)
(lookup stats)
Dates: during 1990-1999
Sort By: most recent first
(reverse)
...though library officials say there is nothing to worry about, employees say concerns about silica dust--a potential carcinogen--in the air have not been adequately answered...
...touch down near Mars' south pole, one of the few spots on the freeze-dried planet that is likely to contain some water. Just before reaching the Martian atmosphere, the lander will release a pair of tapered pods, each about the size of a basketball, made of brittle silica. Plunging ahead of the ship, the projectiles will free-fall to the surface and strike the ground at 400 m.p.h...
...through cracks in the crust, getting progressively hotter. It doesn't boil, despite temperatures reaching up to 400 degrees C, because it is under terrific pressure. Finally, the hot water gushes back up in murky clouds that cool rapidly, dumping dissolved minerals, including zinc, copper, iron, sulfur compounds and silica, onto the ocean floor. The material hardens into chimneys, known as "black smokers" (one, nicknamed Godzilla, towers 148 ft. above the bottom...
...earth's crust, known as plates, are colliding. Generally the weaker oceanic plates are forced beneath the thicker continental slabs. The friction of grinding rock, combined with heat welling up from the earth's interior, transmutes the lower edge of the oceanic plate into magma. Thick with silica, this type of magma tends to solidify near the surface, forming domes and plugs that seal off the channels through which the magma rises. Such blockages turn a volcano into a giant pressure cooker. At a certain point, when the surrounding rock is no longer strong enough to hold the expanding magma...