Shield volcanoes form from eruptions of flowing lava. The lava spreads out and builds up volcanoes with broad, gently sloping sides. The shape resembles a warrior's shield. Cinder cones build from erupting lava that breaks into small pieces as it blasts into the air. As the lava pieces fall back to the ground, they cool and harden into cinders that pile up around the volcano's vent.
Cinder cones are very small cone-shaped volcanoes.
For 2 months the volcano showed signs that it was waking up from its 123-year sleep. Earthquakes beneath the mountain increased. Steam and ash erupted. All these warning signs signaled that magma was moving upward inside the volcano. Rock and ice slide down the mountain.