The island was discovered in 1460 by a Genovese captain Antonia Noli on behalf of Henry the Navigator and the Portuguese Crown, and was first called São Filipe. It gained its current fiery name before the 1680 eruption, since "The Andalusian Merchant" by Thomas Weelkes, who died in 1623, sings "how strangely Fogo burns, amidst an ocean full of flying fishes".
One of the southernmost islands in Cape Verde, Fogo is located between the islands of Santiago and Brava. Practically the whole island is a stratovolcano that has been periodically active: it last erupted in 2014. So the island is nearly round and about 25 km in diameter. The largest volcanic feature is a 9-km-wide caldera, which has walls 1 km high. The caldera has a breach in its eastern rim, and in the centre a resurgent dome with an ash cone that forms the highest point of the island: its summit is about 100 m higher than the surrounding caldera wall.
Pico do Fogo is the highest peak of Cape Verde, rising to 2,829 m above sea level. It is an active stratovolcano. The main cone last erupted in 1675. The only deadly eruption was in 1847 when earthquakes killed several people. Fogo is a hotspot volcanic island. Its most recent eruptions of subsidiary vents have occurred in 1951, 1995 and 2014. It is the youngest and most active volcano in the Cape Verde Islands, a short chain of volcanic islands that generally are younger at the western end, formed as the African Plate moved towards the east over the hotspot.
The 1995 eruption began on the night of 2–3 April, covering the island with a cloud of ash. Residents were evacuated from Chã das Caldeiras inside the caldera, as their homes were destroyed. Residents reported that the eruption was preceded by small earthquakes which increased in magnitude and frequency through April 2 and just after midnight, fissures opened on the flank of Pico. One resident said it looked as if the cone had "been cut by a knife." The eruption began with Strombolian activity, quickly followed by a 'curtain-of-fire' lava fountain that fed a flow which cut off the road to the village of Portela. The 1,300 people living inside the caldera fled during the night to the safety of villages on the north coast. No one was killed, but about 20 people required medical attention.
During the day on April 3, the island was engulfed by a thick cloud of dark ash that reached 2.5 to 5 km high. The initial flows were pāhoehoe lava, although their extent was apparently small. The violent eruption produced lava bombs up to 4 m across that were ejected as far as 500 m from the vents. On April 4 a new scoria cone formed that was open to the southwest and fed a growing ʻaʻā flow. On April 5, the new 'a'a flow reached the western caldera wall and destroyed more houses and the main water reservoir. The eruption became steadier after the first few days, and moderate, Hawaiian-style lava fountains built a spatter cone more than 140 m high. The flows were 'a'a, and flowed towards the west to the caldera wall, then turned north.
The Fogo volcano returned to activity in 2014, having started erupting shortly after 10 a.m. of Sunday, 23 November 2014. There had been a few days of heightened seismic activity, but they worsened beginning at 8 p.m. on Saturday night. The population of Chã das Caldeiras, totaling around 1,000 inhabitants, spent the night outside their homes due to the strong earthquakes, and started being evacuated when the eruption began.
On 30 Nov, the eruption, although quieter for a few days, resumed at dawn. Lava also closed the only alternative route between the Parque Natural de Fogo and the village of Portela. Travelling at ~20 m per hour, the flow destroyed dozens of homes, a large area of agricultural land, and the museum of the Parque. By 2 Dec, the lava flow passing through the village of Portela had destroyed the primary school, hotels, and several additional houses. After 24 hours of remaining stagnant, the flow began again on 2 Dec, reportedly moving at ~9 m per hour. By 8 Dec about 90% of Bangaeira and 95% of Portela had been overtaken by the lava flow. After moving through the towns, the lava-flow front was ~300 m wide.
Fogo volcanism decreased on 9 Dec. The lava flow stopped ~3.5 km from the settlement of Fernão Gomes (~5 km directly N of Pico do Fogo and just short of a steep downward slope to the towns of Cutelo Alto and Fonsaco, on the NE coast of Fogo).
Bruno Faria, a Cape Verdean vulcanologist, said the intensity of the eruption surpassed that of the 1995 eruption, and approached that of the 1951 eruption, one of the strongest ever recorded on the island.
After 77 days of activity, the eruption stopped on 8 Feb 2015.
Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is also called lava. The molten rock is formed in the interior of some planets, including Earth, and some of their satellites. The source of the heat that melts the rock within the earth is geothermal energy. When first erupted from a volcanic vent, lava is a liquid at temperature from 700 to 1,200 °C.
A lava flow is a moving outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its properties.
The physical behavior of lava creates the physical forms of a lava flow or volcano. More fluid basaltic lava flows tend to form flat sheet-like bodies, whereas viscous rhyolite lava flows forms knobbly, blocky masses of rock.
ʻAʻā is one of the basic types of flow lava. ʻAʻā is basaltic lava characterized by a rough or rubbly surface composed of broken lava blocks called clinker. The Hawaiian word is also spelled aa, aʻa, ʻaʻa, and a-aa. It originates from Hawaiian meaning "stony rough lava", but also to "burn" or "blaze".
The loose, broken, and sharp, spiny surface of an ʻaʻā flow makes hiking difficult and slow. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface. At the leading edge of an ʻaʻā flow, however, these cooled fragments tumble down the steep front and are buried by the advancing flow. This produces a layer of lava fragments both at the bottom and top of an ʻaʻā flow.
Accretionary lava balls as large as 3 m are common on ʻaʻā flows. ʻAʻā is usually of higher viscosity than pāhoehoe. Pāhoehoe can turn into ʻaʻā if it becomes turbulent from meeting impediments or steep slopes. ʻAʻā lavas typically erupt at temperatures of 1,000 to 1,100 °C
Pāhoehoe, meaning "smooth, unbroken lava", is basaltic lava that has a smooth, billowy, undulating, or ropy surface. These surface features are due to the movement of very fluid lava under a congealing surface crust.
A pāhoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. It also forms lava tubes where the minimal heat loss maintains low viscosity. The surface texture of pāhoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture. With increasing distance from the source, pāhoehoe flows may change into ʻaʻā flows in response to heat loss and consequent increase in viscosity. Pahoehoe lavas typically have a temperature of 1,100 to 1,200 °C.
http://volcano.si.edu/volcano.cfm?vn=384010
https://volcanohotspot.wordpress.com/2014/12/03/how-strangely-fogo-burns-amidst-an-ocean-full-of-flying-fishes/
www.wikipedia.org
This Earth Cache is located just at the entrance of the caldera. This spot is a common photo stop on the way into the caldera. You do not have to leave the road. Your guide might know some of the answers to the questions.
Send your answers to the questions to me via the contact sheet or message center. You can log right away, I will contact you if something is wrong. However, answers must be send within a day of logging. Logs without answers will be deleted.
1. Describe the terms Strombolian eruption and Hawaiian eruption in your own words.
2. How was the chain of Cape Verde Islands formed?
3. By whom were the terms Aʻā lava and Pāhoehoe lava introduced as technical terms to Geology? Why does ʻAʻā lava makes hiking very difficult?
4. At the coordinates you stand in front of the Welcome sign to the Parque Natural do Fogo. At the side of the road to the North and East you look at an old lava stream. From which eruption this lava originates. Is it ʻAʻā lava or Pāhoehoe lava? Why do you come to this conclusion?
5. Looking to the East there is a small foot path leading along the lava to a typical round hut. Near your position there is a natural object on the side of the lava stream which immediately catches your eye right next to the path. What do you think it is? Describe its shape, size and color.
6. Looking straight North you see the Pico Grande do Fogo and directly in front you can make out smaller, subsidiary cones. Can you see the vent of the 2014 eruption? If yes, describe its position and height. Which ones would be the vents of the other 2 recent eruptions?
7. The new asphalt road ends approx. at this point and another road continues into the caldera. What material was used to build this road? Describe the texture and color of it.
8. A photo of you or your GPS at his viewpoint would be very much appreciated, but it is optional.
