Latest Cerro Azul Eruption Update from Howard Snell - Charles Darwin Foundation
Subject: Cerro Azul Eruption Update 4
20 September 1998
The lava flow from the radial fissure on the ESE slope of Cerro Azul,
Isabela, Galapagos, Ecuador progressed approximately 2.3 km in 23 hours
between 1230 LGT 17 September 1998 and 1146 LGT 18 September 1998. Dr.
Alan Tye, Head of the CDRS Program for Plant and Invertebrates flew over
the site on Friday and recorded the position of the foot of the lava flow
via GPS from the plane. At that time the foot was at 0d 57.566' S, 91d
14.204'W (middle of readings from 3 separate passes, WGS 84 datum).
Alan reported that the flow has reached the accumulated older flows that
run roughly north/south between Cerro Azul and Sierra Negra. The current
flow had turned southward and was running more towards the sea than
previously reported. On Friday the foot of the flow was 7.6 km from the
ocean (bearing 187d), and 12.3 km from Cabo Rosa (bearing 144 d).
The average rate of movement of the flow between 1246 LGT 15 September and
the first measurement of its 8km length at 1230 LGT 17 September was
approximately 168m/hr. That is about 1.7x the rate of progression the
flow showed between Thursday and Friday (100m/hr). The flow may be
slowing because the foot has now reached much flatter terrain.
The GOES Hotspot Monitoring System has not shown a decrease in activity
since 18 September. If the eruption has continued at the same rate, and
the flow has continued to extend at 100 m/hr since the observations on
Friday, then the foot could have been at about 0d 59.69'S, 91d 13.74'W at
1230 LGT September 20 1998. It would be about 4 km from the sea and 8 km
from Cabo Rosa.
At that position the flow would be threatening a nesting zone of Galapagos
Giant Tortoises known as the San Pedro nesting ground. A research team
from the University of Idaho and Charles Darwin Research Station will
depart from Puerto Ayora at 2200 21 September. The team has been delayed
because some members have bee unable to reach Galapagos. One of the goals
of their trip is to assess the likely impact to populations of tortoises
in the area. While the area directly impacted by the lava flow remains a
small portion of the region's tortoise habitat, suitable nesting areas are
limited.
Tortoises in the region have extremely low reproductive success due to
predation by feral pigs on eggs and hatchlings. If nesting habitat
becomes further reduced as a result of the current eruption, the Galapagos
National Park Service and the Charles Darwin Research Station may increase
their programs of captive breeding and repatriation. The current
apparently slow rate of progression by the flow (100m/hr) reduces the
likelihood that adult tortoises would be unable to avoid the lava.
Therefore potential impacts on nesting habitat are the main concern at the
moment.
Potential Contacts for Further Information:
Volcanic History of Cerro Azul: Terry Naumann (naumann@nevada.edu) and
Dennis Geist (dgeist@uidaho.edu)
The Galapagos National Park Service (png@ga.pro.ec or PNG@ECUA.NET)
The Charles Darwin Research Station (cdrs@fcdarwin.org.ec) and (howard@fcdarwin.org.ec)
Hotspot Monitoring System: Luke Flynn (flynn@kahana.pgd.hawaii.edu)
http://volcano1.pgd.hawaii.edu/goes/about.html - follow links
Howard L. Snell
Program Leader
Associate
Professor
Vertebrate Restoration Ecology Herpetology
Curator
& Ecological Monitoring
University of New
Mexico
Charles Darwin Research Station Albuquerque, NM
Galapagos Ecuador
howard@fcdarwin.org.ec