Polka give way to the two-step and new ragtime dances. Polka dancing enjoyed a resurgence in popularity after World War II, when many Polish refugees moved to the US, adopting this Bohemian style as a cultural dance. Polka dances are still held on a weekly basis across many parts of the US with significant populations of central European origin. It was also found in parts of South America. There are various styles of contemporary polka besides the original Czech dance, which is still the chief dance at any formal or countryside ball in the Czech Republic. One of the types found
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