Square dance club goal is to promote and advance square dance as a recreational activity. Typically clubs accomplish this goal through the following activities: This is not an exclusive list, and square dance clubs are constantly on the look out for new ways to achieve their goals. Associations, partnerships and other cooperative ventures have become increasingly more important to square dance clubs. Membership in square dance clubs seems to have peaked in the late '70s and early '80s, and has gradually decreased since that time. Providing classes and training opportunities is the main activity for the majority of square dance clubs. This activity
Types of volcanic eruptions "Ultra-Plinian." Subglacial and phreatic eruptions are defined by their eruptive mechanism, and vary in strength. An important measure of eruptive strength is Volcanic Explosivity Index (VEI), an order of magnitude scale ranging from 0 to 8 that often correlates to eruptive types. Volcanic eruptions arise through three main mechanisms: There are two types of eruptions in terms of activity, explosive eruptions and effusive eruptions. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra. Effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption. Volcanic eruptions vary widely in strength. On the one extreme