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Revision blog: tectonic hazards

Updated: Apr 14


Tectonic hazards represent one of the most formidable natural phenomena on our planet, caused by dynamic movements of the Earth’s lithosphere (the brittle upper part of the mantle and the Earth’s crust). The Earth’s crust is separated into massive sections called tectonic plates and it is the interaction between these plates that triggers earthquakes and volcanic eruptions, together with accompanying secondary hazards, such as tsunamis. This blog gives an overview of tectonic hazards, outlining some of the causes, impacts and mitigation strategies and is intended as a guide for revision or initial knowledge acquisition for those new to tectonics. Do check out or extensive range of geography tutoring packages, where we delve deeper into all subject areas to help you boost those grades!

 

Causes

Tectonic plates float atop a semi-fluid asthenosphere (the semi-fluid layer lying just below the upper mantle and lithosphere) and are constantly in motion due to forces such as mantle convection (caused by thermal movement in the mantle), gravitational pull (action of gravity as plates move away from mid-ocean ridges), and slab pull (caused by plates being subducted, or ‘pulled down’ into the mantle). Tectonic hazards principally occur at tectonic boundaries where plates move apart (divergent boundaries), collide (convergent boundaries) and move past each other (transform boundaries).



At divergent boundaries, magma rises from the asthenosphere to fill the void left as the plates move apart. This gives rise to volcanic activity and earthquakes, particularly along mid-ocean ridges such as the Mid-Atlantic Ridge.



Convergent boundaries see the subduction of a denser oceanic plate beneath a lighter continental or oceanic plate causing a deep seafloor trench, for example the 11,000m deep Mariana Trench in the North Pacific Ocean. Plate subduction can produce powerful volcanic activity, earthquakes and tsunamis, as stresses build up from the interaction between plates. Compressional stresses at this tectonic boundary may also cause one or both plate edges to buckle up forming mountain ranges, such as the collision between the continental Indian and Eurasian plates, responsible for creating the Himalayan mountain range. Although, there is little volcanism at these continental-continental convergent plates, moderate to severe earthquakes can take place, such as the earthquake that devastated large parts of Nepal in 2015.



Transform boundaries experience the build up of shear stress along fault lines due to the lateral movement of plates. When the plates slip, elastic energy is released in seismic waves, leading to earthquakes. The San Andreas Fault is an example of such a plate boundary and so it is no surprise that San Francisco, which lies on this plate boundary, has experienced several large earthquakes.



Impacts

The impacts of tectonic hazards can be devastating both in the short and long term, causing loss of life, environmental damage, destruction to infrastructure, economic downturns and the displacement of people.  The 2023 earthquake in Turkey near the Syrian border caused widespread casualties, severe damage to infrastructure and exacerbated the effects of the ongoing war in Syria. Volcanic eruptions can lead to the expulsion of gases, lava and ash. Secondary hazards include pyroclastic flows, lahars and ash fall, affecting areas well beyond the immediate vicinity of the volcano. The pyroclastic flows from the Volcán de Fuego eruption in Guatemala in 2018 resulted in the deaths of nearly 200 people. Tsunamis are enormous ocean waves triggered by potent underwater earthquakes or volcanic eruptions. The massive displacement of water caused by marine plate displacement during an earthquake poses severe risks for coastal areas, as shown by the Indian Ocean tsunami of 2004, in which millions of people across multiple countries were displaced ,and approximately 230,000 people died.

 

Mitigation

Despite the unpredictability of tectonic hazards, effective mitigation strategies can minimise their impact and improve societal resilience. Strategies include a combination of preparedness, mitigation and response measures. Seismic monitoring networks, hazard mapping and early warning systems enable communities to anticipate and prepare for hazards, reducing their vulnerability and enhancing their response efficiency. Strict building codes, infrastructural considerations and land use zoning can significantly reduce social and economic vulnerability. The replantation of mangrove forests and raising the height of sea walls have been effective in reducing the impacts of tsunamis in coastal regions. Education is a fundamental tool to empower communities, enabling effective response to tectonic hazards. Education may come in the form of public awareness campaigns and community drills. Following a tectonic disaster, efficient evacuation plans, well-trained search and rescue teams and prompt emergency aid are fundamental in reducing loss. Due to the trans-boundary nature of tectonic hazards, international cooperation and coordination plays an important role in enhancing global resilience to tectonic hazards, through technology transfer, capacity building and aid efforts.

 

Conclusion

In conclusion, tectonic hazards are potent and unpredictable natural phenomena caused by dynamic interactions between tectonic plates, which give rise to earthquakes, volcanic activity and tsunamis. Tectonic hazards and associated secondary hazards pose significant risks to human life, infrastructure, the economy and environment. However, through a combination of technology innovation, enforcement of regulations, education and response planning, communities can build resilience and mitigate the impacts of tectonic hazards.


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