Final answer:
Explosive Eruptive Style occurs in volcanic eruptions with high magma viscosity and volatile content, often at convergent plate boundaries, as seen in Mount St. Helens and Mount Pinatubo eruptions.
Step-by-step explanation:
The conditions necessary for an Explosive Eruptive Style of a volcano typically involve several factors. One key factor is the composition of the magma, which needs to have a high viscosity and a high content of volatiles (gases). When viscous, gas-rich magma ascends to the surface, the gases dissolved within it are no longer able to stay in solution due to the decreasing pressure and expand, leading to explosive eruptions. Another factor that contributes to an explosive eruption is the presence of a constriction within the volcano's conduit, like a cap rock or a dome, which can trap the rising magma. This further increases the pressure until it is released in a catastrophic explosion.
Examples of volcanoes with an Explosive Eruptive Style include Mount St. Helens in the United States, which famously erupted in 1980, and Mount Pinatubo in the Philippines, which had a catastrophic eruption in 1991. These volcanoes occur along convergent plate boundaries, where subduction processes contribute to the generation of gas-rich, viscous magmas that drive explosive eruptions.