Cagua is an active stratovolcano at the NE tip of northern Luzon Island, Philippines. It has a circular summit crater of 1.5 km diameter, with steep, 60-m-high walls, and is locally known as the "Fire Mountain". The volcano might have erupted in 1907, when strong fumarole activity was noted. A phreatic explosion in 1860 may have generated pyroclastic flows. At present, there are thermal areas near the summit crater and on the NW and NNE flanks.

Mount Cagua volcano belongs to the Babuya segment where it is part of a N-S line of the active volcanoes, east of the older, now extinct volcanic range of Northern Luzon.

The lavas of Cagua are basaltic and andesitic in composition and belong to the calcalkaline series.

The volcano has been formed in 3 phases:



1) Effusive eruptions feeding basaltic-andesite and basaltic lava flows between 1.5 and 1.2 Million years ago.

2) Explosive eruptions with thick andesitic pyroclastic flows in the interval from 600,000 - 300,000 years ago. These deposits covered the entire volcano.

3) Recent phreatomagmatic activity producing ash flows.