I think there are few natural processes scarier than earthquakes. The noises are loud, the earth trembles, objects fall around you, buildings shake and crumble, people get injured and die.
The past week has seen two of these phenomena around the world, the latest in Equador where the current death toll reads at 450, and a few days earlier saw another earthquake in an island of Japan where 40 people died.
The heated magma rises towards the crust, where it cools and returns towards the depths, creating convection currents. This in turn generates enormous forces of friction on the crust, which has split into pieces called tectonic continental plates, which continually move in some direction, even by as much as 5 centimetres a year, bumping into and sliding against each other.
This pressure between continental plates keeps building year after year, for decades and centuries, and finally the pressure is so high that the edges of the continental plates move against each other and an earthquake occurs, where all the energy that had been stored is released immediately or over a few days. This can result in the earth splitting, or land on one side sliding over that of the other. This process, after many thousands and millions of years can result in highlands or mountains, like the Himalayas of India and Nepal, or the Rocky Mountains in America.
This pressure can also result in the formation of volcanoes that explode, where the magma is released accompanied by an earthquake. This can result in new lands in the sea, as happened with so many islands in the Pacific.
Those of us of Maltese descent will note immediately that the African continental plate and the Euro-Asian one meet at the Mediterranean, with the boundary between them passing through Malta! This explains why so many earthquakes happen in the Mediterranean (mostly in Greece and Turkey).
Of interest to the Maltese diaspora is that the boundaries between continental plates also pass through New Zealand, which is well known for earthquakes, and the Eastern coast of the American continent, from top to bottom.
On the other hand, one can note that Australia is found in the middle of its own continental plate, and therefore considered to be seismically stable. This does not mean that earthquakes don't happen here, but that they occur at a lower frequency.
Wherever we are, we are living on a planet that is anything but static. The lesson I take from all this is the complexity of nature and just how much we should respect its natural processes which are much larger than we are.
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Naħseb li ftit hawn proċessi naturali li jbeżżgħu daqs terremot. Il-ħsejjes tal-biża', l-art ta' taħt saqajk titriegħed, l-affarijiet ta' madwarek jaqgħu, bini jixxengel u jiġġarraf, u nies iwegggħu jew saħansitra jmutu.
Din il-ġimgħa li għaddiet kellna tnejn minn dawn il-fenomeni madwar id-dinja, tal-aħħar fl-Ekwador fejn s'issa huma stmati li mietu erba' mija u ħamsin ruħ, u ftit ġranet qabel seħħ wieħed fi gżira tal-Ġappun fejn mietu 40.
Dan il-magma msaħħan jitla' lejn il-qoxra fejn jiksaħ u jerġa' jmur lejn il-fond, u għalhekk jifforma ċirki ta' konvezzjoni. Dan jiġġenera forzi enormi ta' frizzjoni (friction) fuq il-qoxra, tant li din inqasmet f'biċċiet li jissejħu platti tettoniċi kontinentali (tectonic continental plates) li kontinwament jiċċaqalu lejn xi direzzjoni, anke 5 ċentimetri fis-sena, u jaħbtu u jħokku ma' xulxin.
Il-pressjoni bejn platt kontinentali u ieħor ikun ilu jinġema għal snin, għexieren jew mijiet ta' snin, u fl-aħħar il-pressjoni tkun tant kibret li t-truf tal-platt kontinentali jiċċaqalqu kontra xulxin u jseħħ it-terremot, fejn l-enerġija li tkun inġemgħet tiġi mitluqa f'daqqa jew f'perjodu ta' xi ġranet. Dan jista jirriżulta fi qsim tal-art, jew li l-art ta' naħa minnhom tirkeb fuq l-oħra. Dan il-proċess wara eluf u miljuni ta' snin jista' jwassal għal għoljiet jew muntanji, bħall-Himalayas fl-Indja u n-Nepal, jew ir-Rocky Mountains tal-Amerika.
Din il-pressjoni tista' wkoll tirriżulta fl-iffurmar ta' vulkan li jisplodi, u l-magma tkun tista' toħroġ akkumpanjata ma' terremot. Dan jista' jirriżulta f'artijiet ġodda fil-baħar, bħal dawk tal-ħafna gżejjer fil-Paċifiku.
Għalina ta' dixxendenza Maltija, ninnutaw mallewwel li l-platt kontinentali Afrikan u dak Ewro-Asjatiku jiltaqa' fil-Mediterran, bil-fruntiera bejniethom tgħaddi dritt minn Malta! Dan jispjega għaliex iseħħu tant terremoti fil-Mediterran (il-Greċja u t-Turkija l-iktar).
Ta' interess ukoll għad-dijaspora Maltija hi li fruntieri oħra jinsabu fi New Zealand li huwa magħruf għat-terremoti, u l-kosta tal-Lvant tal-Amerika minn fuq s'isfel.
Mill-banda l-oħra, wieħed jista' jinnota li l-Awstralja tinsab f'nofs platt kontinentali għalih, u għalhekk dan il-pajjiż jitqies li huwa seismikament stabbli. Dan ma jfissirx li terrimoti ma jsirux hawnhekk, imma jsiru bi frekwenza ferm imnaqqsa.
Ninsabu fejn ninsabu, ngħixu fuq dinja li altru li mhix statika. It-tagħlima li nieħu hi kemm in-natura hija kumplessa u kemm għandna nirrispettaw proċessi naturali li huma ħafna akbar minna.
1http://phys.org/news/2006-03-probing-earth-core.html, retrieved 18/4/2016
2http://www.independent.com.mt/articles/2006-06-25/news/underwater-volcano-discovered-off-sicily-93179, retrieved 18/4/2016
3http://pubs.usgs.gov/gip/dynamic/slabs.html, retrieved 18/4/2016
4https://commons.wikimedia.org/wiki/File:Quake_epicenters_1963-98.png, retrieved 18/4/2016
5https://vassallohistory.wordpress.com/earthquakes-in-malta/, retrieved 18/4/2016
1http://phys.org/news/2006-03-probing-earth-core.html, retrieved 18/4/2016
2http://www.independent.com.mt/articles/2006-06-25/news/underwater-volcano-discovered-off-sicily-93179, retrieved 18/4/2016
3http://pubs.usgs.gov/gip/dynamic/slabs.html, retrieved 18/4/2016
4https://commons.wikimedia.org/wiki/File:Quake_epicenters_1963-98.png, retrieved 18/4/2016
5https://vassallohistory.wordpress.com/earthquakes-in-malta/, retrieved 18/4/2016
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