Magnitude 6.5 Earthquake in Guerrero State, Mexico.

The United States Geological Survey recorded a Magnitude 6.5 Earthquake at a depth of 35.0 km, approximately 4 km to the north of the resort of Rancho Viejo in Guerrero State, slightly before 10.00 am local time (slightly before 2.00 pm GMT) on Friday 2 January 2025. This even was felt across much of southern and central Mexico, with at least two people having died, a 50-year-old woman in Guerrero State, and a 60-year-old man in Mexico City. At least 12 further people were injured by the event. 

The approximate location of the 3 January 2026 Guerrero State 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 in 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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Magnitude 7.8 Earthquake off the coast of the Kamchatka Peninsula, Russian Far East.

The United States Geological Survey recorded a Magnitude 7.8 Earthquake at a depth of 19.5 km off the east coast of the Kamchatka Peninsula in the Russian Far East slightly before 2.00 am local time on Friday 19 September 2025 (slightly before 7.00 pm on Thursday 18 September, GMT). Despite the size of this event, no casualties have been reported, although tsunami warnings were triggered across the Pacific. The event is thought to have been an aftershock of a Magnitude 8.8 Earthquake recorded off the coast of the Kamchatka Peninsula in July this year.

The approximate location of the 19 September 2025 Kamchatka Earthquake. USGS.

The Kamchatka Peninsula lies on the eastern edge of the Okhotsk Plate, close to its margin with the Pacific and North American Plates. The Pacific Plate is being subducted along the margin, and as it does so it passes under the southern part of the Kamchatka Peninsula. This is not a smooth process, the rocks of the two plates continuously stick together then, as the pressure builds up, break apart again, causing Earthquakes.

Simple diagram showing the subduction of the Pacific Plate beneath the Okhotsk Plate along the Kuril Trench. Auburn University.

Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement.. Eventually the pressure builds up to far and the overlying plate snaps back, causing an Earthquake and a tsunami.

Simplified graphic showing tsunami generation along a convergent margin. NASA/JPL/CalTech.

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Magnitude 8.8 Earthquake off the Kamchatka Peninsula

The United States Geological Survey recorded a Magnitude 8.8 Earthquake at a depth of 20.7 km off the southeast coast of the Kamchatka Peninsula in the Russian Far East slightly before 11.25 am local time on Wednesday 30 July 2025 (slightly before 11.25 pm on Tuesday 29 July, GMT). A Magnitude of 8.8 makes this the sixth largest Earthquake ever recorded. Despite the size of this event, no casualties have been reported, although the port of Severo-Kurilsk was inundated by a 4 m wave, causing Russian authorities to evacuate the town, and tsunami warnings were triggered across the Pacific.

The approximate location of the 30 July 2025 Kamchatka Earthquake. USGS.

The Kamchatka Peninsula lies on the eastern edge of the Okhotsk Plate, close to its margin with the Pacific and North American Plates. The Pacific Plate is being subducted along the margin, and as it does so it passes under the southern part of the Kamchatka Peninsula. This is not a smooth process, the rocks of the two plates continuously stick together then, as the pressure builds up, break apart again, causing Earthquakes.

Simple diagram showing the subduction of the Pacific Plate beneath the Okhotsk Plate along the Kuril Trench. Auburn University.

Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement.. Eventually the pressure builds up to far and the overlying plate snaps back, causing an Earthquake and a tsunami.

Simplified graphic showing tsunami generation along a convergent margin.NASA/JPL/CalTech.

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Magnitude 7.0 Earthquake off the coast of Northern California.

The United States Geological Survey recorded a Magnitude 7.0 Earthquake at a depth of about 10.0 km a little  over 50 km off Cape Mendocino in Humboldt County, California, slightly before 10.45 am local time (slightly before 6.45 pm GMT) on Thursday 5 December 2024. There are no reports of any casualties associated with this event, but the size and location of the Earthquake led to a tsunami being issued, advising about half a million people in California to seek high ground (in the event no tsunami was recorded), and minor damage to highways and buildings were recorded in several places, as well as disruption to power networks which left about 10 000 people in Humbolt County without power. The initial Earthquake has been followed by a large number of aftershocks, with the USGS estimating there is a 5% chance of another quake with a Magnitude of 6.0 or greater occurring in the same area within a week, and a 34% chance of a quake with a Magnitude of 5.0 or greater occurring.

The approximate location of the 5 December 2024 California Earthquake. USGS.

California is extremely prone to Earthquakes due to the presence of the San Andreas Fault, a tectonic plate margin that effectively bisects the state. The west of California, including Santa Barbara and Los Angeles, is located on the Pacific Plate, and is moving to the northwest. The east of California, including Fresno and Bakersfield is on the North American Plate, and is moving to the southeast. The plates do not move smoothly past one-another, but constantly stick together then break apart as the pressure builds up. This has led to a network of smaller faults that criss-cross the state, so that Earthquakes can effectively occur anywhere.

Goods knocked from shelves in Hoby's Market & Deli in Scotia, California, following a Magnitude 7.0 Earthquake on 5 December 2024. Dylan McNeil/The Times Standard/AP.

However, the 5 December 2024 Earthquake happened close to the southern part of the Mendocino Fracture Zone, a westward extension of the San Andreas Fault, where the Gorda Plate to the north is moving westward relative to the Pacific Plate to the south. Along this boundary the rocks of the two plates continuously stick together, then become stressed as the motion of the two plates draws them apart. This stress builds up until the rocks are forcibly snapped apart, which we experience as Earthquakes.

A crack is seen on Blue Slide Road in Rio Dell, California, following a Magnitude 7.0 Earthquake on 5 December 2024. City of Rio Dell/ABC News.

The Gorda Plate, along with the Explorer and Juan de Fuca Plates are remnants of an ancient oceanic plate, the Fallaron Plate which has almost completely disappeared beneath North America. The Fallaron Plate formerly diverged from the Pacific Plate along the Fallaron Ridge, but as the plate has been subducted both it and the ridge have broken up. The remnants of the plate are now the Explorer Plate in the north, then the Juan de Fuca Plate, then the Gorda Plate in the south. This borders onto the Pacific Plate along the Mendocino Fracture Zone, which extends on land as the San Andreas Fault.

North of California the San Andreas Fault becomes the Mendocino Fracture Zone. USGS.

Witness accounts of quakes can help geologists to understand these events and the rock structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) you can report it to the USGS here. 

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Volcanic eruption on the Reykjanes Peninsula, Iceland.

On 11 November 2023 residents of the town of Grindavík on the Reykjanes Peninsula, Iceland, were evacuated from their homes following a major increase in seismic activity beneath the nearby Fagradalsfjall Volcano. The evacuations were triggered by the discovery of a magma tunnel running directly beneath the town at a depth of about 1.5 km. This is about 12 km long, originating near Stóra-Skógfell hill, and running beneath the town and some way out to sea. Seismic activity in the area has remained high in the area in the intervening weeks, although some people had begun to return to their homes. 

Slightly after 10.15 pm on Monday 18 December 2023, a new volcanic fissure opened on the peninsula, spewing vast amounts of lava and prompting a new series of evacuations. The fissure is about 3.5 km in length, and about 3 km from the town of Grindavík. It is currently producing 100-200 m³ of lava per second, although this is not flowing towards the town, and is not thought to present a threat to Human life.

Lava spewing from a new volcanic fissure on the Reykjanes Peninsula, Iceland, which opened on Monday 18 December 2023. BBC.

Although dramatic, lava flows are not usually considered particularly dangerous, as their advancing fronts are quite slow and can quickly be outpaced by an able-bodied Human being. The more deadly volcanic events are pyroclastic flows, such as the one which engulphed the Roman town of Pompeii, in which clouds of superheated gas and ash move downhill at high speeds in an avalanche-like motion, and phreatic explosions, caused by bodies of lava encountering bodies of water, which evaporate almost instantly, causing huge explosions.

People watching a lava flow on the Reykjanes Peninsula, Iceland, this week. Kristin Elisabet Gunnarsdottir/AFP/Getty Images.

Iceland lies directly upon the Mid-Atlantic Ridge, a chain of (mostly) submerged volcanoes running the length of the Atlantic Ocean along which the ocean is splitting apart, with new material forming at the fringes of the North American and European Plates beneath the sea (or, in Iceland, above it). The Atlantic is spreading at an average rate of 25 mm per year, with new seafloor being produced along the rift volcanically, i.e. by basaltic magma erupting from below. The ridge itself takes the form of a chain of volcanic mountains running the length of the ocean, fed by the upwelling of magma beneath the diverging plates. In places this produces volcanic activity above the waves, in the Azores, on Iceland and on Jan Mayen Island. All of this results in considerable Earth-movement beneath Iceland, where Earthquakes are a frequent event.

The passage of the Mid-Atlantic Ridge beneath Iceland. NOAA National Geophysical Data Center.

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