Which geologic period lasted for almost 7/8 of earth’s history?
a. the carboniferous period
b. the phanerozoic eon
c. the quaternary period
d. the precambrian time

Gemstones are commonly found in pegmatites, which are igneous rocks that are a. exceptionally mafic b. exceptionally coarse grained c. exceptionally fine grained d. extrusive, forming from lava

What was the great rift valley formed by

Acivilization exists for several hundred yeaars, developing its own language. such a civilization probably has been: a. farming corn b. suffering from a lack of contact with the outside world. c. isolated by mountains or some other physical barriers. d. starving from lack of trade.