The Azores Global Geopark is situated at the triple junction between the North American, Eurasian and African tectonic plates. Its geomorphology is therefore primarily shaped by volcanic and tectonic forces. There have been 26 volcanic eruptions since the early 15th century when the Portuguese first settled the islands, which number 16 major polygenetic volcanoes, most of them silicic while some feature summit caldera subsidence. Nine are still active. In addition there are over 1,700 monogenetic volcanic features dispersed either along the flanks, on the summits of the polygenetic volcanoes, or in some 11 basaltic fissure systems. Features here include domes, tuff rings and cones, maars, scoria and spatter cones. Built heritage includes old manor houses, monasteries and churches as well as several fortresses that bear testimony to pirate attacks in the 16th and 17th centuries. All were constructed with volcanic rocks. Whaling, which was once an important activity in the Azores, has also left a valuable cultural heritage.