Diabase is formed when a mass of magma (underground lava) undergoes a slow cooling and crystallization process at depth.
(Diabase; is formed; T:when a mass of magma (underground lava) undergoes a slow cooling and crystallization process at depth) (a mass of magma; undergoes; a slow cooling and crystallization process; T:at depth)
Diabase a mass of magma
is formed undergoes
T:when a mass of magma (underground lava) undergoes a slow cooling and crystallization process at depth
a slow cooling and crystallization process T:at depth