Square dance square dance, very rarely are two modern Western dances ever alike. Like traditional square dancing, recovering from occasional mistakes is often part of the fun. Dancers are encouraged to dance only those programs at which they are reasonably proficient, the default level of achievement being the Mainstream program. All programs are set by Callerlab, the callers' international association, which also governs the training of callers. Irish and Scottish dances are normally done to traditional tunes. English dances may be done to traditional tunes, though, especially at ceilidhs, there is experimentation with many different musical styles. The two types of American
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