Jet stream - an upper atmosphere wind which blows in a narrow band from west to east.  http://www.srh.noaa.gov/jetstream/global/jet.htm

Joints - natural crack in a rock running vertically between bedding planes.

Jurassic -a geologic time period lasting from 208m to 144m years ago.

Juvenile water -water that originated within the earth and was brought to the surface by intrusive vulcanism.