| Uksichan(noun, name, volcano, geology) |
| Ulawun(noun, name, volcano, geology) |
| Uliaga(noun, name, volcano, geology) |
| Ulleungdo(noun, name, volcano, geology) |
| Ulreung(noun, name, volcano, geology) |
| Umboi(noun, name, volcano, geology) |
| Ungaran(noun, name, volcano, geology) |
| Unknown Source(expression, name, volcano, geology, history) |
| Unzendake(noun, name, volcano, geology) |
| Upolu(noun, name, volcano, geology) |
| Urataman(noun, name, volcano, geology) |
| Uratman(noun, name, volcano, geology) |
| Ushishur(noun, name, volcano, geology) |
| Ushkovsky(noun, name, volcano, geology) |
| Usulutan(noun, name, volcano, geology) |
| Utila Island(expression, name, volcano, geology, history) |
| Uwayrid(noun, name, volcano, geology) |
| Uzon(noun, name, volcano, geology) |
| Vailulu'u(noun, name, volcano, geology) |
| Vakak Group(expression, name, volcano, geology, history) |