Modern western square dance of "patter calls" and "singing calls", the two types of square dance calls. The logos shown on the right are the international square dance logo and the modern Alliance of Round, Traditional and Square-Dance logo. Modern western square dancing is a non-competitive activity. There are no dance competitions, and apart from fun events, no prizes are ever offered or sought for 'best dancer' or 'best square'. Particularly at the 'challenge' levels there is large degree of personal satisfaction to be gained from the problem solving element of completing a dance. At all levels the main elements are to enjoy the
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