This 150 year period next saw the eruption of less silica-rich lava in the form of andesitic ash that formed at least eight alternating light- and dark-colored layers.(p216) Blocky andesite lava then flowed from St. Helens' summit crater down the volcano's southeast flank.(p216) Later, pyroclastic flows raced down over the andesite lava and into the Kalama River valley. It ended with the emplacement of a dacite dome several hundred feet (~200 m) high at the volcano's summit, which filled and overtopped an explosion crater already at the summit.(p217) Large parts of the dome's sides broke away and mantled parts of the volcano's cone with talus. Lateral explosions excavated a notch in the southeast crater wall. St. Helens reached its greatest height and achieved its highly symmetrical form by the time the Kalama eruptive cycle ended, in about 1647.(p217) The volcano remained quiet for the next 150 years.