Here's why:

* Explosive eruptions: Mount St. Helens is known for its explosive eruptions, which are characterized by rapid releases of energy and the ejection of ash, gas, and rock fragments.

* High viscosity magma: The magma beneath Mount St. Helens is very viscous (thick), which traps gases and leads to pressure build-up. When this pressure is released, it causes a violent explosion.

* The 1980 eruption: The famous 1980 eruption of Mount St. Helens was a prime example of a violent eruption. It produced a massive lateral blast that devastated a large area and killed 57 people.

* History of eruptions: Mount St. Helens has a history of explosive eruptions, indicating a tendency towards violent activity.

While other volcanoes may exhibit more effusive eruptions, the characteristics of Mount St. Helens clearly place it in the category of violent volcanoes.