An ice crystal usually having an aspect ratio greater than 2 and as much as 100 and with hexagonal symmetry, although trigonal (threefold) and occasionally other symmetries occur. As such crystals fal
l through the clouds in which they form, they may encounter conditions causing them to develop dendritic extensions, that is, become plane-dendritic crystals. (Or platelet.)
In plate tectonic theory earth history, at its simplest, is one of plates rifting into pieces diverging apart and new ocean basins being born, followed by motion reversal, convergence back together, s
ubduction of the oceanic crust, plate collision, and mountain building. This cycle of opening and closing ocean basins is the Wilson Cycle . [Wikipedia]
The theory supported by a wide range of evidence in which the Earth's crust is composed of several large, thin, relatively rigid plates that move relative to one another. The interaction of the plates
at their boundaries causes seismic and tectonic activity along these boundaries.
A collection of components which can bepositioned and oriented as a single unit. A platform may contain otherplatforms. For example, a spacecraft is a platform which may have componentsthat can be art
iculated and are also considered platforms.