Bill (weapon) Bill (weapon) The bill is a polearm weapon used by infantry in medieval Europe. The bill is similar in size, function and appearance to the halberd, differing mainly in the hooked blade form. Other terms for the bill include English bill, bill hook or bill-guisarme. Derived originally from the agricultural billhook, the bill consisted of a hooked chopping blade with several pointed projections mounted on a staff. The end of the cutting blade curves forward to form a hook, which is the bill's distinguishing characteristic. In addition, the blade almost universally had one pronounced spike straight off the top like
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