Eruption in Fernandina Island, Galapagos Cruises & Tours News

By: Eric Castro

GENERAL BACKGROUND

Fernandina Island is the westernmost island of the Galapagos Archipelago. It is one of the youngest and most active volcanos of our planet.

There are no human settlements on the island.

Fernandina Island holds only one visitor site: Punta Espinoza (located on the northeast corner of the island)

This shield volcano raises 1,476 meters above sea level (4,842 feet)

Previous eruption took place between January and April 1995.

Island volcanos behave very differently than continental volcanos

The overall amount of gas is low (in comparison to continental volcanos). Thus, eruptions lack high explosivity (like Reventador, Mount Saint Helen's, Etna, etc).

In island volcanos, lava does not come out from a single vent. Eruptions on island volcanos are mostly through fissure eruptions. These fissures can be radial or circumferential.

The crrent eruption started on Friday, May 13th, 2005. A circumferential fissure located on the southern flank of the volcano is the source of molten rock. Height of the fissure lies at about 1,100 meters above sea level (4,000 feet).

Current fissure has a length of 6 Km (4 miles). The eruption looks like a linear water fountain that bursts out the molten rock upwards. Maximmum height of the fountaining lava has reached 8-10 meters (25-30 feet).

The current fissure is located on the outer flanks of the volcano (as opposed towards the caldera floor). This is why the lava, once flowing, slopes down the volcano.

When fissures are small (short), eruptions are prolonged because lava has a small area of escape. This is why 1995's eruption lasted almost 4 months. Then, once the small fissure opened, a spatter cone was formed and it held the molten rock as the eruption continued (pretty much like a very active melting pot of the most orange/red gravy you'll ever see). A month later, the walls of the cone broke, and the lava started flowing to the coastline. It took one week for the lava to reach the ocean.

When fissures are long (like that of the current eruption) the eruption tends to be short, since all the molten rock has a long area to escape. The flows did run for about 7 Km (4.5 miles) but not enough material to reach the shoreline. The flows stopped about 5 Km (3 miles) from the coast.

The crust of these lava flows cools off rather slowly, and it creates an isolating layer. Underneath, lava continues liquid for at least one more month until it totally cools off.

If you want to know more about past eruptions on Fernandina, click: http://www.volcano.si.edu/...num=1503-01=&VErupt=Y&VSources=Y&VRep=Y&VWeekly=N&volpage=var#bgvn_2001

QUESTIONS AND ANSWERS:

Is an eruption dangerous? By all means. All eruptions are dangerous. Nevertheless, there are eruptions less dangerous than others, like those of island volcanos. These are not too explosive.

What happens with plant and animal wildlife of the island? Nothing survives the force of a lava flow. The main reason is the high temperature (t can be as hot as 2,000?C). Eruptions are normal processes in island biology. They are inevitable and hard to predict when they wll occur.

Is it good to have eruptions? Certainly. Eruptions should be looked like a "cleaning evolutionary mechanism". Although, nothing survives, this new land allows natural replacement of species (i.e.: climax versus pioneers). It is at this level where natural selection acts on those who survive and those who arrive.

Are ship's itineraries modified? Very likely. The Galapagos National Park allows ships to modify their itineraries in order to witness the uniqueness of a Galapagos eruption. Best viewing hours are in total darkness. The best, perhaps, is to get up at 04h30, watch the eruption colors, the lava flowing, and little by little the arrival of the new day at sunrise. The powerful and colossal volcano will finally reveal its face.

Why are there so many clouds when the lava reaches the water? The abrupt temperature change cools off lava almost immediately, but the high temperature of the lava evaporates sea water at super sonic speeds. These clouds are 90% water vapor, and 10% volcanic gas.

How long will the eruption last? Hard to say. What the M/V Santa Cruz and Yacht Isabela II Galapagos Cruises witnessed over the weekend is a sign that eruptions are the hardest things to forecast. For example, the M/V Santa Cruz Galapagos Cruise saw the flows at 04h00 on Saturday May 14th, the Yacht Isabela II Galapagos Cruise saw very little activity on Sunday evening, May 15th. The main fissure has ceased all volcanic activity. As the lava continues to slowly move under the already formed crust, some may break out and it would seem that eruption continues. This can probably be seen for the next two weeks. Due to the massiveness of Fernandina, and the location of where the ship may be, these localized bursts will be invisible to the naked eye.

Where can I see a radial or circumferential fissure? If you visited Genovesa Island (Tower), the walk at Prince Philip Steps has a distinct area where we normally stop the groups to look for the short-eared owl. We normally sit in minute hills in front of a large crack that runs forever. The crack is only 2-3 meters wide (7-10 feet). This crack is a radial fissure. Several examples of circumferential fissures can be found along Darwin Bay, Genovesa Island.

When will the next eruption be? We wish we knew. It is impossible to determine exactly when it will happen. Island volcanos give very little warnings. Plus, these are very fast events. The Galapagos volcanos, however, have eruptions every 6 years.

If there is no eruption, is the volcano dead? Never. Geologists say..."there is no such thing as an extinct volcano". And they are right. There are volcanos that have been "dormant" for hundreds of years, and suddenly produce a catastrophic explosion (for example, Montserrat in the Caribbean). What is true is that volcanos that are found in an active area, and have not erupted in historic times, carry the biggest threats and worst consequences. Any volcano can become reactivated. GalÃ?pagos examples of activity (without permanent eruptions) include, Sierra Negra, Alcedo, Cerro Azul, Roca Redonda, and in the continent we include, Pichincha, Cotopaxi, Antisana, Cotacachi, Sangay, Sumaco, among others.

ALL INFORMATION COMPILED BY FRANCISCO DOUSDEBES, GALAPAGOS EXPEDITION MANAGER

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