Even if you activate "Blasting the Ruins" and an effect is chained that reduces your Graveyard to less than 30 cards, "Blasting the Ruins" still resolves because the condition was correct at the time of activation.
Even if you activate "Blasting the Ruins" and an effect is chained that reduces your Graveyard to less than 30 cards, "Blasting the Ruins" still resolves because the condition was correct at the time of activation.