Lava Caves and Pit Craters
Two other volcanic features commonly seen by visitors
are lava tunnels and pit craters. As lava flows downslope, the top
often cools and forms an insulating crust that keeps the interior
lava hot and running. As the eruption subsides, the molten lava
drains out of the end, living a hollow chamber that can be many
kilometers in length. These tubes have smooth sides with grooves
that show different levels of lava. Such lava tubes can be seen
in the highlands of Santa Cruz, and there
is one just outside of Puerto Ayora. Pit craters are giant sink-holes
that were never eruptive. These formed when subterranean magma chambers
were emptied and the roofs collapsed. Classic pit craters are found
at Los Gemelos in the Santa Cruz highlands.
The Galapagos Islands are considered to be one
of the most volcanic regions in the world, and in recent years
there have been small eruptions at Fernandina and Marchena. In
1979 there was a major, eruption of Volcan Cerro Azul. Benjamin
Morrell, captain of theTartar, described a spectacular
eruption of Fernandina in 1825.
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