Smithsonian Institution
Global Volcanism Network Bulletin v. 20, no. 5, May 1995

Fogo (Cape Verde)  Increased explosive activity; intense fumarolic emissions

SW Cape Verde Islands, Atlantic Ocean
14.95N, 24.35W; summit elev. 2,829 m
All times are local (= GMT - 3 hours)

Eruptive activity that began at Fogo on 2 April generated lava
flows throughout the month (Bulletin v. 20, nos. 3-4).
Approximately 1,300 people evacuated from the Cha Caldera following
fire fountaining from a fissure on the SW flank of the Pico cone.
Lava flows covered the small settlement of Boca de Fonte (figure 4)
by 9 April, and were ~500 m from Portela village a week later.

Cape Verde scientists reported on 19 April that all of the
flow-fronts had stopped, explosive activity had decreased, and
emission of pyroclastic material was intermittent. By that time a
small pit formed near the W flank of the scoria cone and sent
pahoehoe lava W on top of the first aa flows. West of Monte Saia
these new lava flows spread laterally and overrode the N and S
margins of the earlier aa flows. On 10 May three more houses were
covered by flows S of Boca de Fonte. Fumarolic activity from late
April through early May remained intense along the main NE-SW
fault. Inhalation of volcanic gases caused throat and eye
irritations, headaches, and other complaints.

Following a request by the Cape Verde government, volcanologists
from Azores University arrived at Fogo on 11 May to assess public
health problems related to the eruption. Until 14 May pahoehoe and
toothpaste lava flows continued advancing S of Boca de Fonte and
towards Portela village, while gases rose continuously from the
main vents. On 14 May at 1600 the activity increased and an ash
cloud rose 500 m. Measurements made the next day at the end of a
lava tube 2 km W of the main vent showed lava velocities of 2
m/minute. Ropy pahoehoe lavas formed at this stage. The lava
flow-front 10 m away from the lava tube had a velocity of 2 m/hour.
Starting at 1900, and continuing for at least 5 hours, explosions
in the scoria cone crater ejected blocks to heights of 30 m; most
fell near the crater rim.

Several profiles were made of the caldera on 16 May to evaluate CO2
soil degassing using colorimetric tubes fixed in a 1-m-long probe.
Values obtained 70 cm below the ground surface were always <2%.
Ground temperatures changed from 67 to 115 deg C inside the SW
craters where some explosions took place in the beginning of the
eruption. Sulfur deposits could be observed in this section of the
main fissure, but fumarolic activity was already very weak.

On the morning of 17 May dense clouds of gas and dust were released
from the scoria cone while all the lava fronts appeared to be
stationary. Through the afternoon explosive activity increased and
strong explosions gave rise to discontinuous projections of spatter
that reached 50 m high. Due to the explosions some large blocks of
the crater wall collapsed and clouds of orange and red dust rose
~100 m. Streams of gases flowed down the SW slope of the scoria
cone and reached the caldera wall on 18 May. People in the caldera
felt nose and throat irritations >2 km from the main vents, making
it impossible to approach without a gas mask. A strong sulfur smell
was reported as far as Patim village, 8 km SW. On this day
atmospheric samples were collected near the scoria cone. Chemical
analysis of water from springs at Mosteiros (~9 km N) and wells in
Sao Filipe (~15 km WSW) showed no contamination of the reservoirs
by magmatic components.

Since the beginning of the eruption, lava flows have covered ~4.3
km^2 of productive land, and preliminary data indicate an erupted
volume of 22-35 x 10^6 m^3. Boca de Fonte (population 56) was
completely destroyed, and flow-fronts were 300 m from Portela as of
18 May. About 1,000 persons remain in shelters at Army camps in Sao
Filipe, Patim, Achada Furna, and Mosteiros. During this eruption
nobody was killed, but several needed medical assistance, mainly
for respiratory problems due to inhalation of volcanic gas and

Information Contacts: J.L. Gaspar, T. Ferreira, R. Coutinho, and G.
Queiroz, Departamento Geoci ncias, Universidad dos Acores, rue da
Mae de Deus 58, 9500 Ponta Delgada, Acores, Portugal (Email:; A. Mota Gomes, Instituto Superior de Educac~o de Cabo
Verde (ISE), Cape Verde.

Correction: The Instituto de Investigac~o Cientifica de Tropical
(IICT) (Bulletin v. 20, no. 3) is a Portuguese research
institution, not Cape Verdean.

Figure 4. Map of Fogo (Cha Caldera) showing lava flows from the
current eruption as of 18 May 1995. Courtesy of Joao Gaspar,
Universidade dos Acores.