Pumice rocks are igneous rocks which were formed when lava cooled quickly above ground.
(Pumice rocks; are; igneous rocks which were formed) (igneous rocks; were formed; T:when lava cooled quickly above ground) (lava; cooled quickly; L:above ground)
Pumice rocks igneous rocks lava
are were formed cooled quickly
igneous rocks which were formed
T:when lava cooled quickly above ground
L:above ground