, the era of man, including the time during which man attained his highest civilization (perhaps the past 30,000 years), to the present.
Geology
, the history of the earth as read in the rocks.
Geyser
, a boiling spring which periodically sends forth jets of water, steam and gas.
Glacier
, a slow moving river of ice, remnant of the last ice age, generally found flowing down the mountain peaks.