EOS Volcanology Logo Fernandina Volcano, Galapagos Islands

Slide set compiled by Pete Mouginis-Mark, University of Hawaii
INTRODUCTION
The volcanoes on the western Galapagos Islands form one of the main study areas for several members of the IDS Team. In 1989, Pete Mouginis-Mark, Scott Rowland and Lionel Wilson from our IDS Team spent three weeks on Fernandina Island in support of the SIR-C/X-SAR radar missions. In 1993, Howard Zebker used the TOPSAR aircraft radar to collect a digital elevation map of Fernandina and Isabela Islands.

Fernandina makes an interesting comparison to Kilauea volcano, Hawaii, because of the large, deep caldera, the very steep (>35 degree) slopes that are found on the flanks, and the lack of rift zones. As part of our effort to learn more about the evolution of basaltic shield volcanoes, we have been studying Fernandina with field and remote sensing data to identify these differences.

SLIDE #1 (159K): Space Shuttle View
Here we see a photograph taken from the Space Shuttle of the Galapagos Islands. The largest island is Isabela, with Fernandina the smaller island between Isabela and the horizon. This view is to the west.


SLIDE #2 (190K): Fernandina From Shuttle
This is an almost-vertical view of Fernandina from the Space Shuttle. We have added location numbers to show the general location of where the ground photography presented in the following slides were taken.


SLIDE #3 (340K): Shaded Relief
This is a shaded relief map of Fernandina, created with the TOPSAR digital elevation map that Howard Zebker has prepared. We have simulated an illumination direction from the west within the computer to show how steep the flanks are close to the summit caldera. Notice that some of the lava flows are sufficiently thick that the TOPSAR data can measure a difference in relief between the lava flows.


SLIDE #4 (146K): North Profile
As we approached Fernandina Island on our fishing boat, Scott Rowland had this fine view of the northern flanks of the volcano. This is a classic view of the "soup bowl" profile that is typical on these Galapagos volcanoes, and is very different from the profile of Mauna Loa and Kilauea in Hawaii.


SLIDE #5 (200K): 1968 Ash
Fernandina experienced a major episode of caldera collapse in 1968. When climbing the northwest flank of the volcano (Pt. #1 on the location photo), one encounters large areas of ash that have been deeply gullied by subsequent rainfall. Volcán Ecuador can be seen in the background.


SLIDE #6 (226K): 1968 Airfall Deposit
Also at Pt. #1, Lionel Wilson found this fine exposure of some of the 1968 airfall deposits that have been exposed in the wall of one of the stream valleys.


SLIDES #7a,b,c (528K Total For Three Images): Caldera Views
Although it's a real pain to climb to the summit with backpacks made heavy with tents, water and field gear, the view from the rim is spectacular! The caldera of Fernandina is about 3 km x 5 km in diameter, and over 1,100 m deep. These three views give a general impression of what the rim looked like in September 1989. All shots were taken from Pt. #2 on the location photo.


SLIDE #8 (208K): Caldera Floor
In September 1988 (i.e., 12 months before we visited the island), there was an intracaldera avalanche and eruption that resurfaced much of the floor. The avalanche deposits are very hummocky with several collapse pits.


SLIDE #9 (242K): Caldera Wall
A telephoto lens provides an interesting view of the many lava flows that comprise the inner wall of the caldera. These flows are quite thick (3 - 5 meters) and are contiguous for much of the width of the caldera, implying that they were intracaldera flows ponded within an earlier caldera that was once much more shallow than it is today.


SLIDE #10 (369K): Dike in Wall
There are many circumferential fissures close to the rim of the caldera. Here we see exposed in the caldera wall a dike that appears to be related to these fissures. The dike width was estimated to be about 2 meters, and is at Pt. #3 in the location map.


SLIDE #11 (199K): 1982 Lava Flow
The most recent flank eruption on Fernandina took place in 1982 from one of the circumferential fissures (Pt. #3 on location map). Here is the upper part of this flow. Sierra Negra volcano is in the background.


SLIDE #12 (245K): 1968 Block
The caldera collapse in 1968 was accompanied by big phreatic eruptions that ejected large blocks onto the rim of the caldera. Here we see one of the larger ones that we found at Pt #3.


SLIDE #13 (228K): Northeast Flank
Using our fishing boat for transportation, we also sailed to the northeast tip of the island and then hiked in-land. Here we see a general view of this flank, taken from Pt. #4 on the location photo. This is a mosaic of two separate images.


SLIDE #14 (256K): A'a is fun!
It's really miserable trying to get around on the flanks of Fernandina (which is why we like remote sensing so much!). Here we see Pete Mouginis-Mark struggling over yet another a'a lava flow at Pt #4 on the map.


SLIDE #15 (227K): Pahoehoe lava
There is remarkably little pahoehoe lava on Fernandina Island, presumably because the eruptions are characterized by high effusion rates. Here, Duncan Munro is standing on a small patch of toothpaste pahoehoe close to the coast near Pt. #4 on the map. Volcán Wolf is in the background.


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