Seven confirmed deaths as Cyclone Kenneth hits Comoros Mozambique.

Seven people have been confirmed dead as Cyclone Kenneth swept over parts of the Comoros Islands and northern Mozambique this week. The storm passed to the north of the Comoros Islands on Wednesday 24 April 2019, bringing sustained wind speeds (wind speeds maintained for a minute or more) of up to 140 km per hour and extensive flooding to the island of Anjouan, as well as the northern part of Grande Comore, with local authorities reporting three deaths and a number of injuries. The following day the storm hit the coast of Mozambique, passing over the island of Ibo where it killed two more people and destroyed around 90% of all housing, then hitting mainland coast in Cabo Delgado Province, where it caused two further known fatalities, one in the city of Pemba and one in Macomia District. The storm is reported to have caused four ships to sink off the coast of Mozambique, though all crew members have now been reported safe.

Damage caused by Cyclone Kenneth in Moroni, the capitol of the Comoros, following the passage of Cyclone Kenneth to the north of the Islands this week. Anziza M'Changama/AP.

Cyclone Kenneth hit the coast of Mozambique only weeks after Cyclone Idai, which brought extensive flooding to the south of the country, and caused over 700 deaths in Mozambique, Zimbabwe and Malawi. Kenneth is considered to have been the larger of the two storms, in terms of energy released, which translates into higher winds, more rain and larger storm surges, and indeed is one of the largest storms to hit East Africa since records began, however the region where it made landfall is much less densely populated, so it is unlikely to have caused a similar number of fatalities, though many thousands are thought to have been made homeless by the storm.

Damage caused by Cyclone Kenneth in the city of Pemba in northern Mozambique. Neidi de Carvalho/UNICEF.

 
Tropical storms (referred to as Cyclones in the Indian Ocean) are caused by solar energy heating the air above the oceans, which causes the air to rise leading to an inrush of air. If this happens over a large enough area the inrushing air will start to circulate, as the rotation of the Earth causes the winds closer to the equator to move eastwards compared to those further away (the Coriolis Effect). This leads to tropical storms rotating clockwise in the southern hemisphere and anticlockwise in the northern hemisphere.These storms tend to grow in strength as they move across the ocean and lose it as they pass over land (this is not completely true: many tropical storms peter out without reaching land due to wider atmospheric patterns), since the land tends to absorb solar energy while the sea reflects it.

 Damaged cars in Moroni following the passage of Cyclone Kenneth. Anziza M'Changama/AP.

Despite the obvious danger of winds of this speed, which can physically blow people, and other large objects, away as well as damaging buildings and uprooting trees, the real danger from these storms comes from the flooding they bring. Each drop millibar drop in air-pressure leads to an approximate one centimetre rise in sea level, with big tropical storms capable of causing a storm surge of several meters. This is always accompanied by heavy rainfall, since warm air over the ocean leads to evaporation of sea water, which is then carried with the storm. These combined often lead to catastrophic flooding in areas hit by tropical storms.

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Eruption on Mount Karthala.

Mount Karthala is the southernmost, and larger, of two shield volcanoes making up the island of Grand Comore (Ngazidja). Shield volcanos are broad, dome-shaped, volcanoes made up of successive layers of lava; shield volcanoes do not have the classic 'cone-shape' of stratovolcanoes, but can be far larger. Karthala reaches 2361 m above sea-level and has a central caldera 3 km by 4 km. It is an extremely active volcano, frequently producing lava-flows and ash-falls. Ash-falls from Karthala often cause water-contamination problems.

Map 0f Grande Comore showing the position on Karthala. Red line shows the limits of a proposed national park around the volcano. Ramsar.

On the night of 9-10 May 2012 residents of the villages of Mde and Mkazi, to the west of the volcano, reported seeing incandescence on the summit of Karthala, though there has been no reported activity since.

Karthala was last active between April 2005 and January 2007. This cycle started with a series of tremors on the morning of 16 April 2005, followed by the eruption of an ash column from the volcano in the afternoon, followed by ash-falls across the eastern side of the island. This continued into the next day causing local authorities to evacuate some eastern villages, then stopped abruptly during the next night; subsequent investigations on the summit revealed a substantial lava-lake had formed in the caldera.

On 24-25 November activity resumed on the volcano, with an ash-cloud spreading southeast of the summit, with ash-falls reaching the capitol, Moroni. The cloud reached 11 600 m in height, and the Toulouse Volcanic Ash Advisory Center issued an advisory limit to air-traffic. Again a number of villages were evacuated, and concern was raised about water contamination were raised. A large number of people reported respiratory problems, which were reported to have caused the death of a child. Seismic activity (earthquakes) continued until 8 December, when they stopped abruptly.

On 28 May 2006 a lava fountain was observed in the caldera, which persisted till the 31st. This was accompanied by a rise in seismic activity, and a red cloud seen over the summit, reaching a height of 3 km. Earthquake activity rose sharply again in October, causing local authorities to issue an evacuation warning, but no eruption followed.

On 12-13 January 2007 a series of tremors were felt on the island, and an ash cloud was seen over the summit, again a lava lake was seen to have formed in the caldera.

View of the lava lake in the caldera of Mount Karthala on 31 May 2006, taken during a South African Army fly over of the summit. Juile Morin/Volcan-Actif.

The Comosos Islands are considered to be hotspot volcanoes, located over a magma plume which originated deep in the Earth's mantle which is rising through the overlying African Plate, though they may be connected to the East African Rift Zone, which extends from the Red Sea to the coast of Mozambique, roughly a thousand kilometers southwest of the Comoros.

See also The magma chamber beneath the Erta Ale Volcano, Earthquake off the coast of Mozambique, Earthquake shakes Lake Turkana in Kenya, Eruption in the Zubair Archiapelago, in the southern Red Sea and Volcanoes on Sciency Thoughts YouTube.

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