Magnitude 4.7 Earthquake off the coast of Petite-Terre Island, Mayotte.

The United States Geological Survey recorded a Magnitude 4.7 Earthquake at a depth of 10.0 km, roughly 7 km to the southwest of Petite Terre Island in the Mayotte Archipelago, an overseas Department of France in the Mozambique Channel between the Comoros Islands and Madagascar, slightly before 4.15 am local time (slightly before 7.15 am GMT) on Saturday 9 February 2019. There are no reports of any damage or casualties associated with this event, but it may have been felt locally.

The approximate location of the 9 February 2019 Mayotte Earthquake. USGS.

Geologically Mayotte forms the oldest part of the Comoros Island Chain, which are 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 kilometres southwest of the Comoros. Volcanism is thought to have first started beneath what is now Mayotte about 15 000 years ago, and persisted until about 5000 years ago, with the islands rising above sealevel about 7000 years ago, and continuing to grow after the cessation of volcanism due to the accretion of Coral reefs. Although all volcanic activity on the islands ceased thousands of years ago, the islands are still subject to occasional seismic events (Earthquakes), associated with the movement of magma deep beneath the hotspot. These can be potentially hazardous, due to the nature of the rock which makes up the island, mostly poorly consolidated volcanic ash, which is prone to liquefaction when sufficiently shaken; a Magnitude 5.0 Earthquake in 1993 is thought to have caused about €1.7 million in damage, mostly to privately owned homes.

 

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

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Pair of Earthquakes to the east of the Mayotte Islands.

The United States Geological Survey recorded two Earthquakes to the east of Grande-Terre (or Maore) Island in the Mayotte Archipelago, an overseas Department of France in the Mozambique Channel between the Comoros Islands and Madagascar, on Saturday 26 May 2018. The first had a Magnitude of 4.9 and occurred at depth of about 10 km roughly 48 km to the east of the island slightly after 2.30 am local time, and the second had a Magnitude of 5.2 and occurred at a similar depth about 31 km to the east of the island slightly after 11.30 am local time (slightly after 9.30 am local time). Both were felt on the island, but neither caused any damage or casualties.

The approximate location of the 26 May 2018 Mayotte Earthquakes. USGS.

Geologically Mayotte forms the oldest part of the Comoros Island Chain, which are 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 kilometres southwest of the Comoros. Volcanism is thought to have first started beneath what is now Mayotte about 15 000 years ago, and persisted until about 5000 years ago, with the islands rising above sealevel about 7000 years ago, and continuing to grow after the cessation of volcanism due to the accretion of Coral reefs. Although all volcanic activity on the islands ceased thousands of years ago, the islands are still subject to occasional seismic events (Earthquakes), associated with the movement of magma deep beneath the hotspot. These can be potentially hazardous, due to the nature of the rock which makes up the island, mostly poorly consolidated volcanic ash, which is prone to liquefaction when sufficiently shaken; a Magnitude 5.0 Earthquake in 1993 is thought to have caused about €1.7 million in damage, mostly to privately owned homes.

 

This year has seen a series (or swarm) of Earthquakes in the area to the east and southeast of Mayotte, which may indicate the movement of magma beneath the surface, and possibly a future eruption somewhere in the Commoros. Such an eruption would not necessarily occur in the area where the Earthquakes are happening, as magma can migrate significant distances horizontally as well as vertically before erupting or becoming emplaced beneath the surface (i.e. setting to become hard rock without ever erupting).

 

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt these events; if you felt the first quake then you can report it to Earthquake Report here, and if you felt the second you cab report it here.

 

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Magnitude 4.5 Earthquake to the southeast of Mayotte Island.

The United States Geological Survey recorded a Magnitude 4.5 Earthquake at a depth of 10.0 km, roughly 20 km to the southeast of Grande-Terre (or Maore) Island in the Mayotte Archipelago, an overseas Department of France in the Mozambique Channel between the Comoros Islands and Madagascar, slightly before 6.30 am local time (slightly before 4.30 am GMT) on Sunday 13 May 2018. There are no reports of any damage or casualties associated with this event, but it was felt across much of Mayotte.

The approximate location of the 13 May 2018 Mayotte Earthquake. USGS.

Geologically Mayotte forms the oldest part of the Comoros Island Chain, which are 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 kilometres southwest of the Comoros. Volcanism is thought to have first started beneath what is now Mayotte about 15 000 years ago, and persisted until about 5000 years ago, with the islands rising above sealevel about 7000 years ago, and continuing to grow after the cessation of volcanism due to the accretion of Coral reefs. Although all volcanic activity on the islands ceased thousands of years ago, the islands are still subject to occasional seismic events (Earthquakes), associated with the movement of magma deep beneath the hotspot. These can be potentially hazardous, due to the nature of the rock which makes up the island, mostly poorly consolidated volcanic ash, which is prone to liquefaction when sufficiently shaken; a Magnitude 5.0 Earthquake in 1993 is thought to have caused about €1.7 million in damage, mostly to privately owned homes.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

See also...

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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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