Polka such as accordion, fiddle, diatonic accordion, hardingfele and nyckelharpa. Bedřich Smetana incorporated the polka in his opera "The Bartered Bride" () and in particular, Act 1. While the polka is Bohemian in origin, most dance music composers in Vienna (the capital of the vast Habsburg Austro-Hungarian Empire, which was the cultural centre for music from all over the empire) composed polkas and included the dance in their repertoire at some point of their career. The Strauss family in Vienna for example, while probably better-known for their waltzes also composed polkas that have survived obscurity. Josef Lanner and other Viennese composers
Types of volcanic eruptions Types of volcanic eruptions Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three different types of eruptions. The most well-observed are magmatic eruptions, which involve the decompression of gas within magma that