3 A smaller river joining a main river. (9)
  4 A group of islands. (11)
  6 Hawaiian word for lava with a smooth, billowy or ropy surface. (8)
  7 A column of gases, ash and larger rock fragments rising from a crater. (13)
  9 Rocks formed by the laying down of layers of silt or other material. (11)
10 A basin-shaped volcanic depression at least a mile in diameter. (7)
11 A great sea wave produced by a submarine earthquake or volcanic eruption. (7)
12 A submarine volcano. (8)

  1 A ........... volcano is one built by a single eruption. (11)
  2 Name for rain, snow, sleet or hail falling from the sky. (13)
  5 A body of land almost surrounded by water. (9)
  8 A body of igneous rocks with a flat bottom and domed top. (9)