Question: On what date did the 1980 eruption of Mount St. Helens, in which "Crater Glacier" was formed, occur?
Sentence (from "1980 eruption of Mount St. Helens"): The eruption was preceded by a two-month series of earthquakes and steam-venting episodes, caused by an injection of magma at shallow depth below the volcano that created a large bulge and a fracture system on the mountain's north slope.
Relevant evidence: No