Fogo, the youngest and most active volcano in the Cape Verde Islands, lies at the western end of a short chain of volcanic islands off the west coast of Africa. These islands were formed as the African Plate moved eastward over a hot spot, in much the same way that the Hawaiian-Emperor chain formed as the Pacific Plate moved west-northwestward over the Hawaiian hot spot.
The island of Fogo itself is a nearly round, single volcano, roughly 15 miles in diameter. Its summit caldera, Cha das Caldeiras, extends 6 miles north-to-south, and 4 miles east-to-west. Within this caldera is a large composite cone, Pico de Fogo, which rises 9,281 feet above sea level.
Cha das Caldeiras is bounded by steep, nearly vertical walls on its north, west, and south sides but is breached on its east side, where lava can flow to the ocean. The cause of the breach is because of large-scale flank failure similar to what occurred in the Kealakekua region of South Kona.
On Nov. 23, at 10 a.m. local time, an eruption began from Pico de Fogo after almost 20 years of quiet. When Fogo erupted in 1995, staff from the U.S. Geological Survey Hawaiian Volcano Observatory responded to the eruption at the invitation of the U.S. Ambassador to the Cape Verde Islands.
Residents reported that the Nov. 23 eruption was heralded by small earthquakes, beginning a few days before the outbreak of lava. At 8 p.m. on Nov. 22, earthquakes increased in number and size, causing many residents to evacuate their homes and sleep outdoors. Ambient carbon dioxide emission levels at Fogo, normally about 90 tons per day, rose to 300 tons per day before the eruption.
The recent eruption, like the eruptive sequence in 1995, started with moderately explosive Strombolian activity interspersed with fountains of lava. Flows then began erupting from flank vents located near the base of Pico de Fogo.
The currently active vents are within a few hundred yards south of the 1995 eruptive vents. Lava is erupting from three vents near the base of Pico de Fogo and is feeding two large aa flows. One of these flows is moving to the south, away from populated areas. The other lobe is heading northwest, in the direction of inhabited areas and agricultural plots and vineyards.
On Nov. 25, the northwest-moving lava flow encroached upon Portela, a community of about 1,000 people within the summit caldera. An evacuation order was issued as the flow rapidly advanced and threatened the only vehicular access road leading to Portela. Residents who lost access to this road were forced to carry beds, stoves, refrigerators, and all other worldly belongings, to safety by skirting around the margins of actively flowing lava.
To date, roughly half of the homes in Portela have been destroyed by lava. In addition, lava flows have buried the headquarters of Fogo Natural Park, a school and agricultural lands. The greatest loss thus far is the destruction of agricultural lands within the caldera, where commercial vineyards have been covered by lava. This enterprise represented a major source of income for the farming-based community. As the Fogo eruption forges ahead, it continues to threaten the village of Portela, including a storage cellar containing roughly 26, 417 gallons of wine.
Around the world, people often live on or near fertile volcanic soils, which are utilized as productive agricultural lands. For populations with no other options but to live in the shadow of active volcanoes, understanding volcanic processes and monitoring eruptive activity are critical. Such is the case at Fogo.
Kilauea activity update
The lava flow from Puu Oo that began on June 27 remains active and is advancing across state land east of the Wao Kele O Puna Forest Reserve. As of Thursday, the tip of the flow was about 2.4 miles upslope of the intersection of Highway 130 and Pahoa Village Road near the Pahoa Marketplace. There was no significant change in activity at Puu Oo.
The level of the summit lava lake within Halemaumau Crater fell during the early part of the week, mimicking deflation at Kilauea’s summit, but was rising again by Dec. 3, in concert with summit inflation. As of Thursday morning, the lava lake was about 210 feet below the rim of the Overlook crater, up from a low of 230 feet measured two days earlier.
No earthquakes were reported felt in Hawaii during the past week.