The date was May 18 of which year that Mt. Saint Helens erupted, and in which mountain chain is it located?

On the morning of May 18, 1980, a magnitude 5.1 earthquake triggered the largest landslide in recorded history on the north face of Mount St. Helens in Washington state. This cataclysmic event uncorked the volcano, unleashing a massive lateral blast that flattened hundreds of square miles of forest and sent a colossal plume of ash more than 15 miles into the atmosphere. The eruption tragically claimed 57 lives and permanently altered the landscape, lowering the mountain's summit by over 1,300 feet.

Mount St. Helens is one of the most active volcanoes in the Cascade Range, a major mountain chain that stretches from northern California up through Oregon, Washington, and into British Columbia, Canada. This volcanic arc is a segment of the Pacific Ring of Fire, a region of intense seismic and volcanic activity. The volcanoes of the Cascades, including other famous peaks like Mount Rainier and Mount Hood, were formed by the subduction of the Juan de Fuca tectonic plate beneath the North American plate, a process that continues to shape the geology of the Pacific Northwest.