tubes of Tertiary age are known from North Queensland, Australia, some extending for . Lava lakes Rarely, a volcanic cone may fill with lava but not erupt. Lava which pools within the caldera is known as a lava lake. Lava lakes do not usually persist for long, either draining back into the magma chamber once pressure is relieved (usually by venting of gases through the caldera), or by draining via eruption of lava flows or pyroclastic explosion. There are only a few sites in the world where permanent lakes of lava exist. These include: Mount Erebus, Antarctica Erta Ale, Ethiopia Nyiragongo, Democratic Republic of Congo Ambrym, Vanuatu. Lava delta Lava deltas form wherever sub-aerial flows of lava enter standing bodies of water. The lava cools and breaks up as it encounters the water, with the resulting fragments filling in the seabed topography such that the sub-aerial flow can move further offshore. Lava deltas are generally associated with large-scale, effusive type basaltic volcanism. Lava fountains A lava fountain is a volcanic phenomenon in which lava is forcefully but non-explosively ejected from a crater, vent, or fissure. The highest lava fountain recorded was during the 23 November 2013 eruption of Mount Etna in Italy, which reached a stable height of around for 18 minutes, briefly peaking at a height of . Lava fountains may occur as a series of short pulses, or a continuous jet of lava. They are commonly associated with Hawaiian eruptions. Hazards Lava flows are enormously destructive to property in their path. However, casualties are rare since flows are usually slow enough for people and animals to escape, though this is dependent on the viscosity of the lava. Nevertheless, injuries and deaths have occurred, either because they had their escape route cut off, because they got too close to the flow or, more rarely, if the lava flow front travels too quickly. This notably happened during the eruption of Nyiragongo in Zaire (now Democratic Republic of the Congo). On the night of 10 January 1977 a crater wall was breached and a fluid lava lake drained out in under an hour. The resulting flow sped down the steep slopes at up to , and overwhelmed several villages while residents were asleep. As a result of this disaster, the mountain was designated a Decade Volcano in 1991. Deaths attributed to volcanoes frequently have a different cause, for example volcanic ejecta,