Magnitude 6.4 Earthquake off the coast of the Mexico/Guatemala border.

The United States Geological Survey recorded a Magnitude 6.4 Earthquake at a depth of 75.4 km, approximately 17 km off the south coast of the border between Mexico and Guatemala, slightly before 5.40 am local time (slightly before 11.40 am GMT) on Sunday 12 May 2024. This even was felt across much of southern Guatemala, and Chiapas State, Mexico, and triggered a number of small landslides as well as minor damage to some buildings, but there are no reports of any injuries.

The approximate location of the 12 May 2024 Mexico/Guatemala Earthquake. Contour lines show rates of movement during the quake, the red line is the Middle American Trench. USGS.

Mexico is located on the southernmost part of the North American Plate. To the south, along the Middle American Trench, which lies off the southern coast off Mexico, the Cocos Plate is being subducted under the North American Plate, passing under southern Mexico as it sinks into the Earth. Guatemala is located on the southern part of the Caribbean Plate, close to its boundary with the Cocos Plate, which underlies part of the east Pacific. The Cocos Plate is being pushed northwards by expansion of the crust along the East Pacific Rise, and is subducted beneath the Caribbean Plate along the Middle American Trench. This is not a smooth process, and the plates frequently stick together then break apart as the pressure builds up, causing Earthquakes on the process. 

The position of the Cocos, Nazca and Rivera Plates. MCEER/University at Buffalo.

The Cocos Plate is thought to have formed about 23 million years ago, when the Farallon Plate, an ancient tectonic plate underlying the East Pacific, split in two, forming the Cocos Plate to the north and the Nazca Plate to the south. Then, roughly 10 million years ago, the northwesternmost part of the Cocos Plate split of to form the Rivera Plate, south of Beja California.

In a paper published in the Journal of Geophysical Research, in 2012, a team led by Igor Stubailo of the Department of Earth and Space Sciences at the University of California Los Angeles, published a model of the subduction zone beneath Mexico using data from seismic monitoring stations belonging to the Mesoamerican Seismic Experiment, the Network of Autonomously Recording Seismographs, the USArray, Mapping the Rivera Subduction Zone and the Mexican Servicio Sismologico Nacional.

The seismic monitoring stations were able to monitor not just Earthquakes in Mexico, but also Earthquakes in other parts of the world, monitoring the rate at which compression waves from these quakes moved through the rocks beneath Mexico, and how the structure of the rocks altered the movement of these waves.

Based upon the results from these monitoring stations, Stubailo et al. came to the conclusion that the Cocos Plate was split into two beneath Mexico, and that the two plates are subducting at different angles, one steep and one shallow. Since the rate at which a plate melts reflects its depth within the Earth, the steeper angled plate melts much closer to the subduction zone than the shallower angled plate, splitting the Trans-Mexican Volcanic Belt into sections above the different segments of the Cocos Plate, and causing it to apparently curve away from the subduction zone.

Top the model of the Cocos Plate beneath Mexico, split into two sections (A & B) subducting at differing angles. (C) Represents the Rivera Plate, subducting at a steeper angle than either section of the Cocos Plate. The Split between the two has been named the Orozco Fracture Zone (OFZ) which is shown extended across the Cocos Plate; in theory this might in future split the Cocos Plate into two segments (though not on any human timescale). Bottom Left, the position of the segments on a map of Mexico. Darker area is the Trans-Mexican Volcanic Belt, orange circles are volcanoes, brown triangles are seismic monitoring stations, yellow stars are major cities. Bottom Right, an alternative model showing the subducting plate twisted but not split. This did not fit the data. Stubailo et al. (2012).

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Jade mask among items found in Mayan tomb in Guatemala.

A mosaic jade mask is among the items discovered in a 1700-year-old Mayan tomb in Guatemala, according to a press release issued by Tulane University on 29 January 2024. The site, at Chochkitam, close to the borders with Mexico and Belize, was investigated by a team led by archaeologist Fran Blom of the Middle American Research Institute at Tulane University in 1924, but nothing was discovered at that time. In 2022 a series of tunnels was detected in a lidar (Light Detection and Ranging, a system of scanning land surface and near-surface structures from an aircraft using lasers) survey of the area, leading to an investigation on the ground led by Francisco Estrada-Belli of Tulane University. 

A mosaic jade mask discovered inside an ancient Maya tomb dating back 1700 years in Chochkitam, Guatemala, near the borders of what are now Mexico and Belize, on 1 July 2022. Francisco Estrada-Belli/Tulane University.

The tunnels discovered by the lidar survey turned out not to be connected to the tomb, or any other structure, and are thought to have been dug by would-be-looters with some idea that there was a tomb in the area, who eventually gave up before finding it. The actual tomb was located about 2 m from the end of the looters tunnel. This was found to be remarkably intact, although part of the stone ceiling had collapsed, and some natural decay had set in.

The excavation site of an ancient Maya tomb discovered in Chochkitam, Guatemala, near the  borders of what are now Mexico and Belize, on 1 July 2022. The tomb and relics inside date back 1700 years. Francisco Estrada-Belli/Tulane University.

The tomb contains a series of Human femur bones inscribed in a Mayan hieroglyphic script, which identify the occupant of the tomb as a previously unknown Mayan king, listing his father and grandfather, which makes it possible to link him to the Maya states of Tikal in Guatemala and Teotihuacan, to the northeast of Mexico City . The tomb is thought to have been sealed in about 350 AD, and also contains a series of shells of the Mollusc Spondylus, a type of Spiny Oyster, which were used as currency by the Mayans.

Incised femur bone with drawing of the inscription upon it.  Alexandre Tokovinine/Holmul Archaeological Project/Tulane University.

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Over 1000 people evacuated from nearby communities as Mount Fuego erupts in Guatemala.

Over 1000 people have been evacuated from five communities close to Mount Fuego, a 3768 m high stratovolcano (cone shaped volcano made up of layers of ash and lava) that forms part of La Horqueta volcanic complex in the southern part of Guatemala, after a sudden increase in volcanic activity on Thursday 4 May 2023. The volcano produced a column of ash which reached about 5800 m above sealevel (about 2000 m above the summit of the volcano) as well as several pyroclastic flows (avalanches of hot ash and gas). A number of flights had to be diverted away from the region as a precaution, and communities within 7 km of the volcano have been evacuated as a precaution.

An eruption on Mount Fuego, Guatemala, on 4 May 2023. Reuters.

Fuego has been more-or-less constantly active at some level since records in the area began (circa 1524). It forms part of La Horqueta volcanic complex, which also includes the Acatenango volcano to the north, a complex volcano with at least five separate vents, the complex siting on the site of the ancient Meseta volcano, which is thought to have collapsed following a major volcanic episode about 8500 years ago, causing a debris flow that reached the sea, 50 km away.

An ash column over Mount Fuego on 4 May 2023. Reuters.

The volcanoes of Guatemala, and Central America in general, are fed by the subduction of the Cocos Plate beneath the Caribbean Plate along the Middle American Trench, which runs roughly parallel to the southwest coast of the isthmus. As the Cocos Plate sinks into the Earth, it passes under Central America, which lies on the western margin of the Caribbean Plate. As this happens it is heated by the friction and the heat of the planet's interior, causing the sinking plate to partially melt. Some of the melted material then rises through the overlying Caribbean Plate as magma, fueling the volcanoes of Central America.

Diagrammatic representation of the subduction of the Cocos Plate beneath the Caribbean Plate along the Middle American Trench. VCS Mining.

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Magnitude 6.2 Earthquake in Escuintla Department, Guatemala, kills two.

The United States Geological Survey Recorded a Magnitude 6.2 Earthquake at a depth of 83.6 km beneath the town of Nueva Concepción, in Escuintla Department, Guatemala, slightly after 1.10 am local time (slightly after 7.10 am GMT) on Wednesday 16 February 2022. Two people are reported to have died due to this event, both due to heart attacks, a number of buildings have been damaged, and several landslides triggered. People have reported feeling this event across Guatemala and El Salvador, as well as in parts of Honduras and Mexico.

 

 

The approximate location of the 16 January 2022 Guatemala Earthquake. USGS.

Guatemala is located on the southern part of the boundary between the North American and Caribbean Plates, close to their boundary with the Cocos Plate, which underlies part of the east Pacific. The Cocos Plate is being pushed northwards by expansion of the crust along the East Pacific Rise, and is subducted beneath the North American and Caribbean Plates along the Middle American Trench, which runs parallel to the south coast of Guatemala and neighbouring countries, passing under Central America as it sinks into the Earth's interior. This is not a smooth process, the plates tend to stick together, breaking apart again once the pressure from the northward movement of the Cocos Plate builds up to much, triggering Earthquakes.

 

Diagrammatic representation of the subduction of the Cocos Plate beneath the Caribbean Plate along the Middle American Trench. VCS Mining.

 

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Landslides kill more than 50 in Guatemala, as Hurricane Eta sweeps across Central America.

More than fifty people are thought to have died in a series of landslides in Guatemala, with around half the deaths associated with a single event in the town of San Cristobal Verapaz, where a mudslide swept away about 20 houses. Elsewhere, another ten people were killed in a landslide in Huehuetenango Department, two children died when their home was destroyed by a landslide in Santa Barbara Department in the north of the country and a second pair of children died in another landslide incident in Quiche Department, also in the north, while a third pair of children died in a separate landslide in the south of the country. Another landslide in the south has left one person dead and another two missing, while another person died in a landslide close to Guatemala City. All of these landslides have been brought on by heavy rains associated with Hurricane Eta. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. Despite not being directly hit by the storm, Guatemala has suffered badly because of it, with flooding across much of the country, and at least five major bridges, and numerous roads, swept away.

Flooding in Guatemala City associated with Hurricane Eta. Johan Ordonez/AFP.

Across central America about 70 people are thought to have died in incidents related to Hurricane Eta, which was a Category 4 Hurricane when it made landfall, bringing with it winds of up to 225 km per hour, to the south of the city of Puerto Cabezas. Two people are known to have died in Nicaragua as a result, and two in Honduras. In Panama, five people were killed when a landslide buried their homes in Chiriqui Province, close to the border with Costa Rica, while in Costa Rica a 71-year-old American citizen and his 51-year-old Costa Rican wife died in a landslide at Coto Brus in Puntarenas Province. El Salvador has also reported a number of landslides, though no fatalities at the current time.

 

The aftermath of a landslide in Chiriqui Province, Panama, caused by heavy rainfall associated with Hurricane Eta. AFP.

Hurricane Eta has lost energy as it has passed over Central America, and been downgraded from a hurricane to a tropical storm, but it is expected to travel northwest over the next few days, gaining strength again as it passes over the Caribbean, and potentially threatening the populations of Cuba and Florida. The casualty rate was probably been kept down by the evacuation of about 20 000 people from its path in Nicaragua, and Honduras.

 

The path and strength of Hurricane Eta. Thick line indicates the past path of the storm (till 3.00 am GMT on Friday 6 August 2020), while the thin line indicates the predicted future path of the storm, and the dotted circles the margin of error 9, 21, 33, 45, 69, 93 and 117 hours ahead. Colour indicated the severity of the storm. Tropical Storm Risk.

Tropical storms 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.

 

The formation of a tropical cyclone. Natural Disaster Management.

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 1 cm 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. 

 

The formation and impact of a storm surge. eSchoolToday.

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