Catalogue · NOAA volcano catalogue; current eruptions from GDACS
Volcanoes
Volcanoes form where molten rock, magma, reaches the surface. Most sit along plate boundaries, above all in the Ring of Fire around the Pacific; a few sit over hot spots in the middle of plates.
Where magma comes from
The mantle is solid rock, but it melts in three kinds of place: where plates pull apart and the pressure on the rock drops; above a sinking plate, which carries water down that lowers the melting point of the rock above it; and over hot spots, where unusually hot rock rises from deep below.
Kinds of volcano
Runny basalt lava builds broad, gently sloping shield volcanoes like those of Hawaii. Stickier, gas-rich magma at subduction zones builds steep stratovolcanoes such as Mayon in the Philippines and Mount St Helens in the USA, which can erupt explosively.
Reading the map
Each triangle is a volcano from NOAA's catalogue. Colours show the last eruption it records: red since 1964, orange from 1900 to 1963, grey older or unknown. The catalogue is not fully up to date, so a few recently active volcanoes still look older. Some eruptions happening now are reported by the Global Disaster Alert and Coordination System and appear as Events.
Taiwan's volcanoes
The Tatun Volcanic Group, including Qixing Mountain, rises just north of Taipei. Its last known eruption was small, more than 1,000 years ago, but hot springs, gas vents and small earthquakes show heat below, and scientists monitor it continuously and count it as active. Guishan Island off Yilan is also a young volcano.
Did you know?
About 1,350 volcanoes have erupted in the last 10,000 years or so. Many more lie hidden along the mid-ocean ridges on the seafloor.