The kinds of rocks are many and the varieties endless, but, if classified according to their modes of origin, they fall into three major classes: I. Igneous rocks formed by the solidification of molten rock-matter, as exemplified by the rocks formed on the cooling of lava discharged from a volcano.
(The kinds of rocks; are; many) (the rocks; formed; L:on the cooling of lava) (the cooling of lava; discharged; from a volcano) (they; fall; into three major classes) (I. Igneous rocks; formed; by the solidification of molten rock-matter)
The kinds of rocks the rocks the cooling of lava they I. Igneous rocks
are formed discharged fall formed
many
L:on the cooling of lava
from a volcano
into three major classes
by the solidification of molten rock-matter