Ashfall layers in the Philippines: A) Section on the Santo Tomas River bridge north of San Narciso, Zambales; 32 km west-southwest of vent. Layer A is 8 mm of sand-sized ash; layer B is 4 mm of mostly fine ash. Note weak normal grading of layer C and scattered coarse clasts on surface of deposit.

B) Tephra-fall deposits on unimproved road along the Marella River 10.5 km southwest of vent. Layer A, about 4 cm thick, consists of coarse ash and fine lapilli; layer B consists of several thin layers of ash; layer C is 33 cm thick and is the thickest section of the climactic pumice-fall deposit yet found. Note normal grading overall, but 2-cm pumice lapillus in upper left. Layer D consists of two 3- to 4-cm-thick beds of fine ash separated by a bed of water-reworked pumiceous ash.

C) Tephra deposits on unimproved road about 9 km southeast of vent, north side of Gumain River. Layer B is 23 cm thick and consists of numerous graded ash beds; layer C is 31 cm thick and has two zones in lower part with minor fine ash coatings.

D) Section at mouth of Pasig River canyon about 15 km east of vent. Layer B is 10 cm thick and layer C is about 18 cm thick; note ash-rich zones that stand out owing to increased cohesiveness. USGS Images by W.E. Scott and J.J. Major. Larger image.