Cerro Azul Eruption Update 4 - Tortoise Nesting Area Could be Threatened (fwd)

[John Bois <jbois@umd5.umd.edu>]

Is there a parallel to late Cretaceous basalt flows in India, here?


---------- Forwarded message ----------
Date: Sun, 20 Sep 1998 15:52:55 -0500
From: "Howard L. Snell" <howard@FCDARWIN.ORG.EC>
Reply-To: herp-l@ucdavis.edu
To: herp-l@ucdavis.edu
Subject: Cerro Azul Eruption Update 4 - Tortoise Nesting Area Could be  
Threatened

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