Technically Mount Fako is a strato volcano on the coastal end of the much larger (800 square kilometer) Tombel Graben. It is rather misnamed since it is not a Graben really; it is a large caldera with a Graben inside. The caldera floor of the Tombel volcano has been filled in by lava floods. The Tombel volcano has not erupted during historical times, but there was one eruption at Le Djungo about 200 years ago. Tombel has two large strato-volcanoes, Mount Fako at the coast, and Mount Manengouba with its large calderas. There is a young crater row at Mount Manengouba that is believed to have erupted during the last 1 000 years. The Tombel Graben has one of the largest lava reservoirs that have been mapped.
Cameroon Volcanic Line
The Tombel volcano is situated on the Cameroon Volcanic Line. A distinction shared with Oku Volcanic Field, mostly famous for the Lake Nyos disaster. In the other end sits the active volcanic Island of Bioko. The volcanic line is trending from north-east to south-west. It is most likely a fault line that is a remnant from the separation of the continents that trended from the MAR as the Tombel Graben moved away from the centerline of the Atlantic Ridge. It is now cut off from the MAR completely.
Mount Fako today
On Tuesday an earthquake swarm started with epicenters ranging from Mount Fako to the magma reservoirs under the mountain. There is also a trending line of quakes going from the magma reservoirs of the mountain towards the center of the Tombel Graben. At the same time low frequency harmonic tremor started at Tombel Graben, and normal magmatic harmonic tremoring at Mount Fako. The earthquake swarms at Mount Fako before an eruption are normally strong to very strong for being at a volcano, with almost continuous quakes ranging from 2M to 5M before and during an eruption
Before onset of current activities an episode of rapid GPS movement started less than 70 days ago in the Tombel Graben caldera and GPS-movement consistent with inflation at Mount Fako.
On the Friday a set of smaller explosions happened on the flank of the volcano known close to the Hut 2 tourist lodge. The explosions where small and most likely caused by hydrothermal vents blowing out, as pressure increased inside the volcano. Two tourists where lightly injured during one of the explosions.
This has lead to increased surveillance of the volcano. It is the best monitored of the African volcanoes, with permanent local staff, additional French experts, and also equipment from a Power Production Company in place.
If an eruption occurs, it will most likely be on the south west flank. It would be a rather explosive affair ranging from VEI1 to VEI3. After and during the explosive phase there will be a lava flow moving towards the coast.
The authorities in the area are used to the volcano, and the same goes for the residents. If needs be there will be an evacuation of threatened villages, but not much more.
The biggest danger of the volcano is that the earthquakes before and during the eruptions will make houses collapse on top of people. Otherwise the volcano is generally harmless.