The tectonic plates in Mexico are very peculiar because their way of converging is different from that of other regions of the planet.
The Earth's surface did not always look like we do today. The continental masses float on a magma or molten rock, and are divided into plates that rub and collide with each other, which gives rise to mountains, deep sea and earthquakes.
Major tectonic plates
In the year 1620 Sir Francis Bacon, an English philosopher very dedicated to political affairs, but who dedicated the last years of his life to science, noticed how the coasts of the American and European continents on the map fit perfectly.
Based on this, a hypothesis was elaborated in 1912, by the German Alfred Wegener - supported by the fact that similar fossils were found in very distant places on the planet - that the continents moved in a viscous mantle.
Such theories lacked credibility until the 1960s, when the theory of plate tectonics was fully developed.
It was determined that the movement of the plates has been developing for millions of years and that there was a supercontinent called Pangea that grouped all the current continental surfaces, separated thanks to the reconfiguration and constant displacement of the lithosphere.
Various phenomena can occur in plate convergence zones. If one plate moves over another, it is said that there is a subduction and as a result an uplift, producing mountain ranges and volcanoes. If there is a collision, mountains are produced and there is a high level of seismicity or probability of earthquakes occurring.
Some countries like Mexico have part of their territory in various zones or tectonic plates. As a consequence, they are areas of high seismic activity and volcanism.
Mexican tectonic plates
The countries where tectonic plates converge have certain similar characteristics. However Mexico is different.
For example, when plates converge, earthquakes originate at a depth of 600 km, and yet in Mexico an earthquake has rarely been detected below 100 km.
In most subduction zones, volcanic arcs are created parallel to the trench left by the plates. In Mexico this arc moves away from the trench at an angle of approximately 15º.
In most subduction zones, large earthquakes occur every few hundred years. In Mexico it occurs only on the coast, and also a modality called "silent earthquake" has been detected, undetectable and lasting up to one month.
Most of Mexico is located at the bottom of the great North American plate. In the southern part it converges with the Caribbean plate.
This plate covers both the Caribbean Sea and most of the Antilles, including much of Cuba, a part of South America, and almost all of Central America. From Mexico, the Caribbean plate contains southern Chiapas.
The California peninsula is located on the Pacific plate, which moves to the northwest and down from the North American plate. The San Andrés fault is located in the meeting area of these two plates, which is famous for its high seismic activity.
The Rivera plate is a small plate located between Puerto Vallarta and the south of the California peninsula. Its movement is in a southeastern direction, skimming the Pacific plate and submerging under the North American plate.
The Orozco and Cocos plates are oceanic crusts located in the southern part of Mexico. The collision between the two was the cause of the great earthquake of 1985 in Mexico City as well as the most recent earthquake of 2012.
Tectonic plates can have three types of edges between them. They are said to be divergent if the plates move away from each other, leaving a space where volcanic eruptions and earthquakes can occur.
On the other hand, they are convergent when the plates rather meet, one of the following cases may occur:
1- Subduction limit: one plate bends below the other, towards the interior of the earth. This can occur in both the continental and oceanic parts, creating a strip or rift, as well as a mountain and volcanic chain.
2- Collision limit: Two continental plates approach each other, creating large mountain ranges such as the Himalayas.
3- Friction limit:, where the plates are separated by sections of faults that are transformed, giving rise to straight and narrow valleys on the ocean floor.
Plate tectonic concepts
Current theory suggests that plate tectonics are between 5 and 65 kilometers thick.
The earth's crust is divided into approximately twelve plates, which drift in different directions at different speeds, a few centimeters a year, as a result of thermal convection currents in the earth's mantle.
Some of these plates contain land and sea, while others are entirely oceanic.
Concepts about faults
When the forces of the tectonic plates exceed the capacity of the shallow rocks (located 200 km deep), they fracture, giving rise to a discontinuity.
The fault plane is called the rupture zone, and it has a parallel slide of the rocks.
Active faults are those that continue to slide today, while inactive faults have no movement for more than 10,000 years. However, it is not ruled out that an inactive fault could eventually be activated.
If the movement of the fault is gradual and the tension is released slowly, the fault is said to be asismic, while if the movement is abrupt, the fault is said to be seismic. A large earthquake is caused by jumps of 8 to 10 meters between the edges of a fault.
References
- Continental drift, Alfred Wegener. Recovered from: infogeologia.wordpress.com.
- Evolution of Tectonics in Mexico. Recovered from: portalweb.sgm.gob.mx.
- Francis Bacon. Recovered from: biografiasyvidas.com.
- Tectonic plates of Mexico. Recovered from: sabergeografia.blogspot.com.
- Recovered from: www.smis.org.mx.
- Tectonic Setting of La Primavera Caldera. Recovered from: e-education.psu.edu.
- The unusual case of the Mexican subduction zone. Recovered from: tectonics.caltech.edu
- Which tectonic plates affect Mexico? Recovered from: geo-mexico.com.