At about 11.50 pm local time on
Sunday 24 May 2015 the
Instituto Geofísico-Escuela Politécnica Nacional
recorded a sudden rise in seismic activity (Earthquakes) beneath Wolf Volcano,
which is located on the northern tip of Isabella Island in the Galapagos. This
was followed at 2.15 am on Monday 25 May by a major eruption which according to
the
Washington Volcanic Ash Advisory Center, produced an ash column 10.7 km high, that subsequently drifted
65 km to the southwest. A second major eruption at 3.45 am produced a 15.2 km
high plume which drifted 250 km to the east, while a third eruption shortly
after produced a 13.7 km high plume which drifted 250 km to the east. At 4.28
am
NASA’s
MODIS satellite, which monitors infra-red emissions, detected a
significant thermal anomaly on the southeastern flank of the volcano, which
would generally indicate a lava eruption, which was later confirmed by
investigators from the
Galápagos National Park, who reported a new fissure
close to the southeastern rim of the caldera, which was producing several major
lava streams.
The May 2015 eruption on Wolf Volcano. Diego Paredes/AFP.
These eruptions continued
throughout Monday 25 and Tuesday 26 May, before eventually subsiding, producing
significant lava flows and smaller ash columns, as well as several hundred
kilotons of sulphur-dioxide emissions. There was initial concern that the
eruption might present a threat to the volcano’s distinctive fauna; the volcano
is a distinct environment compared to the rest of the island, and hosts a
unique set of animals of its own, including the Wolf Giant Tortoise, Chelonoidis nigra becki, and Pink Land
Iguana, Conolophus marthae, though these are
concentrated on the northwest flanks of the volcano and are unlikely to have
been harmed by an eruption on the southeastern flanks.
A Pink Land Iguana, Conolophus marthae. Alamy.
Wolf Volcano is the highest
volcano in the Galapagos, reaching 1707 m above sea level, with an oval crater
measuring 6 km by 7 km orientated in a northwest-southeast direction. Like all
the volcanos of the Galapagos it is a shield volcano, i.e. a volcano made up
largely of overlapping lava deposits that resembles an upturned bowl rather
than a cone. The placement of this volcano on the northern tip of Isabella
Island creates a unique microhabitat on the northwestern flanks of the volcano,
cut off from the rest of the island by the steep, smooth lava flows of the main
peak. This has served to protect the wildlife of the volcano from invasive
species such as feral Cats and Goats, which threaten much of the unique fauna
of the Galapagos (though Goats have recently been sighted here). As well as its
own unique Tortoise, the Wolf Volcano ecosystem is also home to several
populations of introduced tortoises from other islands, including at least two
possible specimens of the
Pinta Island Giant Tortoise, Chelonoidis nigra abingdoni, thought to have gone extinct with the
death of Lonesome George in 2012, which are currently under investigation by
wildlife geneticists from
Yale University and the
Galapagos Conservatory.
Lonesome George, the last known surviving specimen of the Pinta Island Giant Tortoise, Chelonoidis nigra abingdoni, prior to his death in June 2012. Wikipedia.
The volcanos of the Galapagos are
fuelled by a mantle plume, the Galapagos Hotspot, an upwelling of hot magma
from deep within the Earth’s mantle which pierces the overlying Nazca Plate,
and moves independently of it. This plume transverses the plate at a rate of
0.46 degrees per million years, which has led to the formation of the string of
volcanoes which form the Galapagos Islands. However analysis of the geochemical
composition of the lavas of Wolf Volcano has shown that these are distinct from
the lavas of the neighbouring Ecuador and Darwin volcanoes, but show strong
similarities to lavas produced on the Galapagos Spreading Center over 200 km to
the north, a trait shared with lavas from other Galapagos volcanoes, most notably
Santa Cruz and Genovesa, suggesting that there is some interplay between these
two sources.
Wolf Volcano is the most active
volcano in the Galapagos, it was first observed erupting in 1797 and most
recently in 1982; the 2015 eruption is the eleventh recorded eruption on the
volcano, which is believed to be slightly less than 500 000 years old, compared
to an age of about 10 million years for the surrounding seafloor. It takes its
name from Theodor Wolf, a German geologist who made the first organized study
of the volcanoes of the Galapagos in the nineteenth century, and after whom
Wolf Island is also named.
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