Mount St Helens is located in North America, specifically in the state of Washington in the United States. It is a stratovolcano situated in the Pacific Northwest region of North America.

Location
Mount St Helens is part of the Cascade Range, which extends from northern California through Oregon and Washington. It is located about 50 miles northeast of Portland, Oregon and about 96 miles south of Seattle, Washington. The volcano is nestled within the Mount St Helens National Volcanic Monument, which was established to protect and study the area after the catastrophic eruption in 1980.

Geological History
Mount St Helens is a relatively young volcano, with its first known eruption occurring about 40,000 years ago. It is classified as a stratovolcano, also known as a composite volcano, which is characterized by its steep sides and explosive eruptions caused by the buildup of viscous magma. Over time, the volcano has undergone several periods of activity and dormancy.

1980 Eruption
The most notable event in the history of Mount St Helens is the eruption that occurred on May 18, 1980. This eruption was one of the most significant volcanic events in the history of the United States. It resulted in the loss of lives, destruction of forests, and significant changes to the landscape.

The eruption began with a massive landslide, triggered by an earthquake, which removed the northern flank of the volcano. This sudden collapse of the volcano's side unleashed a powerful lateral blast that devastated the surrounding area, resulting in the destruction of over 230 square miles of forest.

The eruption also produced a massive ash cloud that rose to an altitude of more than 80,000 feet and spread across several states. The ashfall affected air quality, disrupted transportation, and caused significant damage to infrastructure.

Current Activity
Since the 1980 eruption, Mount St Helens has displayed periods of volcanic activity and periods of relative calm. The volcano is closely monitored by scientists to detect any signs of impending eruptions and to better understand the behavior of the volcano.

While Mount St Helens is currently considered dormant, it is still an active volcano with the potential for future eruptions. The area surrounding the volcano is popular among scientists, researchers, and tourists alike, who visit to witness the remarkable recovery of the ecosystem and to study the processes of volcanic activity.