Dynamic landscapes are the features of land caused by the movement of tectonic plates (the sections that divide the Earth’s outer shell). The topic of dynamic landscapes also covers tectonic hazards, their causes, examples, trends and patterns.
The landscapes are dynamic because of mantle convection, subduction and slab pull which move the tectonic plates.
Types of dynamic landscapes
The different types of dynamic landscapes depend on the type of plate boundary.
Rift valleys and ocean ridges
Rift valleys and ocean ridges are formed at divergent plate boundaries (also known as constructive plate boundaries), where the plates are moving away from each other.
As the tectonic plates move away from each other, magma rises from the gap and hardens. When this occurs in oceanic plates, it is called seafloor spreading, and it forms ocean ridges. Due to the movement of the tectonic plates, the newly formed crusts continues to move away from each other. When continental plates move away from each other, they form rift valleys.
Fig. 1 - Jordan Rift Valley, Israel
Triple junctions are where three divergent plates are moving away from each other at an angle of 120 degrees. A good example is the Afar region in northern Ethiopia, where the African, Arabian, and Indian plates are moving away from each other.
Island arcs and oceanic trenches
Island arcs and oceanic trenches are often created at convergent plate boundaries where an oceanic crust meets with another oceanic crust.
Island arcs are created due to the subduction of one of the oceanic plates, which leads to the formation of volcanoes. The lava and debris from the volcanoes accumulates and eventually, the volcanoes grow above sea level. An island arc is a long chain of these volcanoes. An example is the Ring of Fire.
Fig. 2 - volcanic eruption
Ocean trenches are long, narrow valleys in the sea formed as the denser oceanic plate is pushed below the continental plate.
Mountain ranges
Mountain ranges are formed at convergent plate margins where either two continental tectonic plates or continental and oceanic tectonic plates collide. Due to compressional forces, the sedimentary rocks are pushed upwards, causing either one or both plates to buckle up and form mountain ranges. An example is the relatively young Himalayas (formed within the last 100 million years or less).
Fig. 3 - The Himalayas
Fault valleys and undersea canyons
The regions where plates are sliding past each other horizontally are called conservative plate boundaries or transform plate boundaries. The rocks from the plates are pulverised and often create fault valleys (continental and continental plates) or undersea canyons (oceanic and oceanic plates).
Nazaré Canyon, NASA, Public Domain
Natural hazards and dynamic landscapes
Tectonic plates are always either moving against, apart or past each other. Tectonic hazards are threats caused by the movement of tectonic plates that have the potential to cause damage to life, property, the environment, human activity and the economy. These hazards include earthquakes, explosions of volcanoes and tsunamis.
Impact of tectonic hazards
Natural disasters are a consequence of natural hazards. A natural hazard is considered a disaster when it has exceeded a given threshold, meaning it has caused significant damage to society or a community, and they can no longer cope using their own resources. Significant damage includes disruptions to human, material or environmental aspects such as loss of life, injuries, and damage to infrastructure.
Hazards can have social, economic and environmental impacts on society. These include loss of life, injuries, damage to infrastructure, businesses and the ecosystem.
Examples of tectonic hazards caused by dynamic landscapes
The example case studies of tectonic hazards that we will go through with you include:
The Tohoku earthquake and tsunami.
The Gorkha earthquake.
Mount Merapi eruption (2010).
Tectonic disaster trends and patterns
Unlike other natural hazards, the trend of tectonic hazards has not changed over the years. The number of deaths caused by tectonic disasters varies significantly each year as they depend on megadisasters. Economic losses from tectonic disasters are increasing as people are becoming more affluent. Volcanic hazards are not as frequent compared to earthquakes, and the number of deaths is significantly lower.
Tectonic hazard forecasting involves calculating the probability of a hazard occurring in a specific location by monitoring seismic activity and historical information. This knowledge allows governments to prepare. However, accurate tectonic hazard prediction – knowing exactly when and where a hazard will happen – is not possible at the moment. Scientists are working on trying to make it possible by observing magma movement.
Tectonic hazard management involves reducing the number and scale of systemic weaknesses. This includes, for instance, reducing vulnerability and increasing resilience through educating communities on preparation for disasters.
It is not possible to carry out direct tectonic hazard modifications as their forces are too powerful. Realistic modifications could include strengthening infrastructures such as building earthquake-resistant buildings, sea walls and mangroves against tsunamis, and building barriers against lava flow.
Dynamic Landscapes - Key takeaways
- Dynamics landscapes are the features of land caused by the movement of tectonic plates (the sections that divide the Earth’s outer shell).
- Rift valleys and ocean ridges are formed at divergent plate boundaries.
- Island arcs and oceanic trenches are often created at convergent plate boundaries where an oceanic crust meets with another oceanic crust.
- Mountain ranges are formed at convergent plate margins where two continental plates or continental and oceanic tectonic plates collide.
- Conservative plate boundaries or transform plate boundaries form fault valleys or undersea canyons.
- Tectonic hazards are threats caused by the movement of tectonic plates and include earthquakes, explosions by volcanoes, and tsunamis.
- The trend of tectonic hazards has not changed over the years.
- Tectonic hazard forecasting involves calculating the probability of a hazard occurring in a specific location by monitoring seismic activity and historical information. Tectonic hazard prediction is knowing when and where a hazard is likely to happen.
- Tectonic hazard management comprises reducing the number and scale of systemic weaknesses.
- Realistic modifications include strengthening infrastructures such as building earthquake-resistant buildings, sea walls and mangroves against tsunamis, and barriers against lava flow.
References
- Fig 1: Rift Valley (https://commons.wikimedia.org/wiki/File:Israel_Jordan_Rift_Valley_06.JPG) by Zairon (https://commons.wikimedia.org/wiki/Special:Contributions/Zairon) licensed by CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/deed.en)
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