Overview
The purpose of this blog is to examine causes,
effects, and the solutions to tsunami formation in a way that helps the reader
recognize its importance. A look at several of earth’s spheres helps depict a
picture of their interaction. And since the earth is dynamic, change in one
system of the earth can influence the other. Causes of tsunami are either
related to earthquake, volcanoes, and landslides which can be a collaboration
between hydrosphere and geosphere. Since tsunamis are known to displace
water from its equilibrium position, the displaced water can affect humans in
one way or the other. Hydrosphere-geosphere is known to be the major concern in
tsunami formation, this blog will elaborate the interaction between different
component of spheres and the influence in the other corresponding aspect of earth.
What is a Tsunami and how does it work?
Causes of Tsunamis
Earthquakes - Geosphere & Hydrosphere
Earthquake are the primary source of tsunami. This is
due to tectonic activity happening underneath the surface water (Mofield, Symons, Lonsdale, Gonzalez
& Titov, 2004). When an earthquake happens beneath the surface water due to the
collision of tectonic plates, pressure is created, displacing water from its
equilibrium position. Research indicates that when water is displaced from its
original position waves are formed under the influence of gravity (Costa, Leroy, Kershaw,
& Dinis, 2005), hence leading to tsunami formation. This is an example of the
interaction between geosphere and hydrosphere.
Figure 1.
Tsunami in action
Volcanoes - Geosphere, Hydrosphere & Atmosphere
Volcanoes
are also a major cause of tsunami. This can be generated in a subduction zone
through the release of gases from the melting of tectonic plates creating
pressure and pushing gases against the crust. The release of gas create tension
changing the volume of water. This change in pressure displaces the sea water. Alternatively, an area
of a higher temperature within the mantle result in a lower density than the
adjacent magma. The excessive strain and high energy magma melts the crust
hence pressure is created and volcanoes form. Submerged volcanic eruption
displaces the overlaying water causing a tsunami. This is an expression of the
interaction between geosphere, hydrosphere and atmosphere resulting to the formation of tsunami.
Figure 2.
Volcanoes erupting underneath surface water causing tsunami.
Landslides - Geosphere & Hydrosphere
Landslides that generate tsunamis most often occur where
Earth's tectonic plates converge and is compared to the one caused by
earthquake where rocks slides over each other (Herbitz, Lovholt, Pedersen &
Masson, 2006). The dense plates sink underneath the lighter plates which makes Part
of the seafloor snaps upward as the pressure is created. The overlying column
of seawater is elevated and displaced toward the surface, creating a surge of
seawater. This process involving geosphere and hydrosphere creates waves in the
forms of tsunamis as the water reverts to equilibrium state.
Figure 3. Effect of landslide and as the heavy plates sink
underneath the lighter plates causing tsunami.
Effects of Tsunamis
Tsunamis have an impact on the earth dynamic system.
This effect emerges as a result of interaction between the different component
the earth creating a surge movement of water hence leading to destabilize the
soil hence making life uncomfortable for human beings.
Salination - Hydrosphere, Pedosphere & Biosphere
Soil productivity is dependent on water
permeability. According to Ondrasek, Rengel and Veres(2011) excessive mineral
deposition in the soil threatens water infiltration. Sea water contains a large
quantity of minerals in is composition, and when tsunami happens the pedosphere
is exposed to this excessive quantity of minerals. Since sea water contains
large amount of Na+ it replaces soil coagulators absorbed into the
surfaces interfering with the content of other minerals like Mg2+ and
Ca2+ which are essential in retaining nutrients (Rashad and Dalts,
as cited in Ondrasek et al., 2011). Without proper nutrients in the soil, the
habitability of the pedosphere is jeopardized. This
effect the biosphere in such an environment hence making hostile to organism
living on the surrounding region.
Figure
4. Tsunami in action before it turns the soil unproductive.
Death/Disease - Hydrosphere, Anthrosphere & Pedosphere
Tsunamis affect the astrosphere in two ways,
directly and indirectly. The direct impact come because of the force and the
velocity at which water mass flows. Waves produced can travel at a speed of
900km/h (Costa et al., 2005). Subsequently this can have an impact on
infrastructure and livelihood of those residing in the surrounding area.
Illagasekare et al.,
(2006) claim that the
Sri Lanka Tsunami in 2004 caused the loss of approximately 400000 jobs, 85000
homes and claimed a loss of 35000 people. Indirectly tsunamis can contaminate
ground water causing a long-term effect for instance diseases. (Ondrasek et al.,
2011) suggest that increased salinity in aquifer can enhance the solubility of
the water. this can lead to excessive potential contaminants. When tsunami
happens water infiltrates into the soil with high contents minerals salinizing
the underground water. As a result, with large contents of minerals water
becomes unhealthier for consumption. For example, salinity causes mineral
deficiency to the people who are relying on the effected water Ondrasek et al
(2011). In general hydrosphere can influence astrosphere through different
means.
Tsunami Floods in Miyako, Japan 2011
Mitigation of Tsunamis
Mangroves - Biosphere & Hydrosphere
Mangroves - Biosphere & Hydrosphere
The danger of tsunami is primarily derived from the
momentum which the sea water moves and even though with less recommendation
found, mangroves plays significant role in resisting the force induced by the
tsunami. Research indicates that presence of mangroves around coastal areas
destabilizes the tsunami by amplifying the wave height and consequently
reducing velocity at which the mass water flows, hence collapsing the wave (Koh,Teh,Majid
and Lau, 2012). Similarly Danielsen and
others(2005) believes that mangroves and other coastal forests significantly
mitigate the potential damage caused by tsunami. The 2004 Indian tsunami
supports this finding, as reports suggest that coastal vegetation like
mangroves helped provide protection in nearby communities. This shows a clear
evidence between hydrosphere and biosphere interaction in mitigating tsunami.
Figure 5. pre- tsunami tree vegetation cover and
post tsunami damages in Cuddalore District, Tamil Nadu, India.
Tsunami Sirens - Anthrosphere & Hydrosphere
Early warning system (EWS) plays acritical role in
easing the effect of tsunami across the globe. Larsen and Thomalla (2010)
suggest that putting resilience for instance Siren can positively contribute to
a better future in terms of minimising death as well as property. This however
suggest that people responding to that are more likely saver and incur less
problems than those with no resilience measures on the disaster-prone areas.
Arguably Smith and Davies (as cited in Larsen & Thomalla 2010) believes
that people prone to disaster areas do not always respond to warning system and
therefore can respond so that they can be in a better position. Similarly, Hope
(2016) believes that there is an urgent need to put up resilience after the
Kaikoura earthquake. This signals out the level of risk that can evolve as
result of the earthquake and can eventually lead to success in the near future.
This clearly states the role of putting EWS to minimise risk for people
residing along the coastal parts and prone earthquake areas with the likes of
Christchurch.
Figure 6. man responding to the emergency sirens
Conclusion
Tsunamis are a complex and powerful geological process involving the interaction of many spheres of the earth system, from causation to consequence and human efforts to mitigation their effects. Dynamic Interactions between hydrosphere and geosphere, atmosphere (volcanic eruptions, earthquakes and tectonic plate movements) result in the formation of a tsunami. Tsunami pose various detrimental impacts on the Earth's dynamic system including the pedosphere and the biosphere. Due to the anthrospheres dependence on these respective spheres, the anthrosphere also exhibits the consequences of tsunami. With rising concern on the emergence of tsunami, solutions to minimise its consequences are implemented relating to the hydrosphere and the biosphere. Overall the interaction that tsunamis exhibit between different spheres of the Earth shows the dynamic nature of the Earth system.
About
This Blog is a personal
project made by Mohamud Hassan. I am an undergraduate student studying at the
University of Canterbury majoring in Geology. This is part of Geol115 – “The
dynamic Earth system” which is focusing on Travis Horton section of the course.
I hope you enjoyed reading.
Reference list
Reference list
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