Alcedo Volcano
Alcedo | |
---|---|
Geology | |
Mountain type | Shield volcano |
Last eruption | December 1993[1] |
Alcedo Volcano is one of the six coalescing
The volcano has the largest number of wild tortoises of any of the volcanoes in the Galapagos, though their genetic diversity is amongst the lowest of any of the breeds in the archipelago. The habitat of the tortoises was threatened when feral goats crossed from southern Isabela Island in the 1970s and then reproduced rapidly.
Geology
It is believed that Alcedo volcano emerged from the sea approximately 313,000 years ago, based on its sub -aerial volume of 234 km3 and average eruption rate of 1x106 m3 per year.
Alcedo, like the other volcanoes in the Galapagos, has been formed as part of the
It is the only volcano in the Galapagos to have erupted Rhyolite lavas. Approximately 1 km3 of Rhyolite was erupted in total, a small amount compared to its sub-aerial volume. The eruption of this began about 120,000 years ago in a series of eruptions, the largest of these has resulted in a tephra covering on the eastern slopes.[4] Following the rhyolite eruption there has been a return to basaltic lava eruptions. It is theorised that the change in volcanic output is due to the movement of Alcedo away from the hotspot, which has resulted in the changing chemical makeup of the magma being supplied to the magma chamber.[5]
There is a hydrothermal system within Alcedo, the temperature of the water released is less than 97 degrees Celsius, though chemical analysis has shown that the reservoir temperature is over 260 degrees Celsius. The analysis has also shown that the residence time, the time that water remains in the hydrothermal system, is approximately 400 years and that the source of the water is from rainfall.[6]
Wildlife
In a 2003 study of the species of
For many years it was believed that feral goats would not be able to cross the Perry Isthmus, a 12 km wide lava field, from southern Isabela to northern Isabela Island. However, goats were recorded as having crossed this in the early 1970s and by 1998 it was estimated that the population was between 75,000 and 125,000. The goats affected the environment that was detrimental to the native tortoises, eating plants that were the food source for them. The removal of the plants also meant that watering holes dried up. To combat this Project Isabela was undertaken to eradicate the goats from northern Isabela island by the National Park and the Charles Darwin Foundation.[9] The project was completed in 2006 with all goats on northern Isabela Island being removed, following the project there has been a rapid recovery of small trees and shrubs that are associated with the native habitat.[10]
See also
References
- ^ a b c "Alcedo". Global Volcanism Program. Smithsonian Institution.
- ^ .
- ISSN 0094-8276. Retrieved June 16, 2013.
- S2CID 129810886.
- .
- S2CID 129779685.
- ^ Amos, Jonathan (October 3, 2003). "Volcanic blast recorded in DNA". BBC News. BBC. Retrieved June 16, 2013.
- S2CID 39102858.
- ^ "History and Achievements". Charles Darwin Foundation. Retrieved June 16, 2013.
- ^ "Ecosystem Restoration: Project Isabela". Galapagos Conservancy: Conservation: Project Areas. Galapagos Conservancy. Retrieved June 16, 2013.