Imagine a Very Large Volcanic Eruption Occurs,and a 20 Km-Wide

Imagine a very large volcanic eruption occurs,and a 20 km-wide lava flow moves into a valley and separates it into two halves.How might this affect resident species with regard to allopatric speciation?

A) The lava flow area will cause a geographic barrier that promotes speciation among the majority of species populating the area.
B) The effect of the lava flow on allopatric speciation will depend on the identity and traits of the various species present,including their abundance and respective mobility within the valley.
C) The effects of the lava flow on speciation will depend on to what extent the various individuals present at the time can adapt to the new lava in the environment.
D) The lava flow will not cause much allopatric speciation to populations in the area because species that are present will be able to move across and around the lava flow.