Taal lake will play a big role in the big boom....

One of the main concerns with Taal is the abundant water in its two lakes and the extensive underground hydrothermal system the magma and lava could potentially interact with. “When water comes into contact with something hot, it flashes into steam. Water turning into steam is an incredibly energetic change” that causes it to expand by a factor of eight, Gregg says. If that change happens in an underground hydrothermal system, the steam can build up until it explodes. “That’s the scary part,” Johnston says. The initial stages of Taal’s current eruption were, in fact, such steam-driven, or phreatic, ones, and they sent ash high into the sky.

The current eruption also carries a tsunami risk because of the lake surrounding it. If part of the volcano’s flank collapses into the lake, it could trigger such a wave. (A similar event happened in late 2018 at Anak Krakatau in Indonesia, killing more than 400 people, though it was bigger than what Taal could likely generate.) Tsunamis can also be triggered by large, superheated currents of volcanic gas, ash and other debris—called pyroclastic flows—or by mudflows caused as volcanic ash mixes with abundant water. Both of these occurrences can be devastating in their own right, because they can hurtle down slopes much more quickly than the lava people tend to associate with volcanoes.
Will Taal Volcano Explosively Erupt? Here's What Scientists Are Watching - Scientific American