The earliest activity at Tata Sabaya constructed a pyroclastic shield, which crops out as a thick sequence of block-and-ash flows fallout deposits and pumice deposits in the northern sector of the volcano. Effusive eruptions then built up a volcanic cone on top of this shield; the five northerly lava flows were emplaced during this phase of activity. Some lava flows from this stage were unstable and collapsed, covering the northern parts of the volcano with debris.