The elliptical, 10 x 20 km wide Laguna Caldera SE of Manila forms the middle lake-filled basin of the three-pronged, dinosaur-footprint-shaped Laguna de Bay, the largest lake on Luzon Island.  Pre-caldera Pleistocene volcanism formed basaltic to basaltic-andesitic volcanoes, including Talim Island and Mount Sembrano stratovolcanoes on opposite sides of the current caldera.  The caldera, whose lake surface is only 1 m above sea level, may have formed during at least two major explosive eruptions about 1 million and 27,000-29,000 years ago.  Post-caldera volcanism formed maars of young, but unknown age at the southern end of elongated Talim Island, which forms the SW rim of the caldera.  Jalajala is a solfataric field on the flank of Mount Sembrano on the Jalajala Peninsula, which forms the eastern rim of the caldera.