Azken egunotan, Donostian erregistratu diren olatu erraldoien berri izan dugu Euskal Herrian. Tenporala izenarekin ezagututa, berriz ere itsasoak bere boterea erakutsi digu gizakioi. Euskaldun gehienak oso harrituta daude, baina hau al da harritzeko modukoa? Aldaketa klimatikoaren ondorioa apika?

Egia esan, Donostian oso ugariak izan dira tenporal hauek historian zehar eta zorionez, dokumentu grafikoak baditugu. Segidan aurkeztuko diren argazkiek Gipuzkoako hiriburuan urte ezberdinetan jazotako itsas-ekaitzak islatzen dituzte (ezkerretatik eskubitara eta goitik behera: 1923, 1927, 1933, 1935 eta 1944). Eta argi ikusten da azken argazkian olatu handiek eragindako suntsipena Paseo Berrian, egun gertatzen den antzera. Halaber, nire amonak kontatu zidan bere gaztaroan horrelako olatuak gertatzen zirela behin baino gehiagotan, eta halako batean, Donostiako espigoia eraiki zuten baino lehen, olatuak Mirakruz Kalera heldu zirela. Beraz, fenomeno berria ez da, inolaz ere, eta badirudi ez dela areagotu denboraren poderioz.





Hala izanik, esan dezakegu marea bortitz hauek naturalak direla. Eta hona iritsita, mareak sortzearen arrazoiak esplikatzea komenigarria da. Horretarako, Eguzki-Lur-Ilargi sistemara joko dugu. Sistema honetan, gorputz bakoitzak besteak erakartzen ditu grabitatearen bitartez. Baina indar hau distantziaren menpe dago; zenbat eta gertuago, orduan eta indar handiagoa egongo da.

Eguzkia eta Lurra soilik aintzakotzat hartuz gero, goian agertzen den irudi bat edukiko genuke. Goiko marrazkiak Lurra irudikatzen du (zirkulu beltzaren bidez) eta ezkerretara eguzkia kokatu behar genuke. Esan dugun gisan, Eguzkiak Lurrarengan erakartze-indarra aplikatzen du Lurraren zentrutik R distantzia batera; era berean, kontrako norabideko magnitude bereko indar bat sortzen da Lurrean, indar zentrifugoaren izenarekin ezagutzen dena eta Eguzkiaren grabitate-indarra konpentsatzen duena. Indar zentrifugoak intentsitate-balio berak izango ditu Lurraren edozein punturako, grabitatea puntuaren arabera ezberdina den bitartean, Eguzkiarekiko distantzia (R) aldatzen delarik. Adibidez, A punturako, Eguzkiarekiko distantzia jaitsi da R(A) puntura zeinen balioa R(A) = R - Lurraren Erradioa baita; arestian aipatu izan den lez, indarra igotzen da distantzia murrizten den heinean, beraz A puntuan, eguzkiak ezartzen duen indarra handiagoa da Lurraren zentruarekin alderatuz eta honek esan nahi du indar zentrifugaren magnitudea gainditzen duela. C puntuan, aldiz, distantzia R(C) handiagoa da (R(C) = R + Lurraren Erradioa), beraz indarra txikiagoa izango da, berriz indar zentrifugoarekiko desoreka bat sortuz. Amaitzeko, B eta D puntuek zentruaren indar-intentsitate berbera izango dute (R(B) = R(D) = R), baina norabidea zertxobait okertuko da Eguzkiaren zentruaren kokapena dela eta. Honen guztiaren ondorioz, goiko irudiko gezi horiek indikatzen digute zeintzuk diren Lurraren zentruan ezartzen den indarraren eta puntu horien indarren arteko diferentzia. Honek esan nahi du eguzkia nolabait saiatzen dela Lurraz tiratzen marrazkian grisez agertzen den (exageratutako) irudi bat emanez.

Alabaina, Lurra zurruna da eta ezin da modu horretan deformatu; itsasoa, ordea, fluidoa da eta deformatu ohi da hain ezagunak diren mareen bidez. Itsasgora A eta C bezalako puntuetan gertatuko da eta itsasbehera, B eta D puntuen longitude bera duten edozein tokitan.

Hala ere, Eguzkia ez da mareak sortzen dituen eragile bakarra, ezta garrantzitsuena ere. Hori Ilargiaren esku gelditzen da, zeinek, masa askoz ere txikiagoa daukan arren (indarra masa handiagoekin ere areagotzen da), Lurretik oso hurbil kokatzen denez gero, marea handiagoak sortzeko gai baita. Ideia bat izan dezazuen, eguzkiaren ondorioz sortutako mareak ilargiaren ondorioz sortutakoak baino % 46 txikiagoak dira, gutxi gora-behera.

Orduan, Ilargia mareen eragile nagusia dugu eta dakigun bezala, gorputz honek fase berezi batzuk aurkezten ditu hilabetero. Fase hauen existentzia Eguzki-Lur-Ilargi sistemaren kokapenari hertsiki lotuta daude. Hala, ilberria dagoenean, Ilargia Lurra eta Eguzkiaren artean kokatzen da; era honetan, Eguzkiak argitzen du Lurretik ikusten ez dugun Ilargiaren partea (hau da, Ilargiaren aurpegi urruna). Guretzat, Ilargia ilun agertzen da. Ilbetea dagoela esaten dugunean, berriz, Lurra kokatzen da sistemaren erdian, beraz Eguzkiak guretzat ikusgarria den Ilargiaren partea argitzen du (Ilargiaren aurpegi hurbila). Tarteko faseetan, Ilargia ez dago ez Lurraren aurrean, ez Lurraren atzean, irudiak erakusten duen gisan.

Hau esanda, zein fasetan espero zenukete marea handienak kokatzea?




- Ilberria (goiko irudia) eta Ilbetea (beheko irudia): hauek ematen direnean, esan den legez, Eguzkia eta Ilargia norabide berean daude (syzygy-n), Ilargia Lurraren aurrean edo atzean egonda ere. Honek suposatzen du Ilargi zein Eguzkiaren erakartze-efektua areagotu egingo dela Lurrean eta deituriko udaberri-marea edo ingelesez spring-tide izugarriak eratuko dira.





- Ilgora eta Ilbera: Ilargia eta Eguzkia ez daude syzygy-n edo norabide berean; beraz, Ilargiak ezartzen duen erakartze-indarra perpendikularra da eguzkiak ezartzen duenarekiko. Hau dela medio, nolabait bi indar horiek gehiago orekatzen dira eta marea baxuagoak sortzen dira, marea hilak edo ingelesez neap tide kontzeptuarekin ezaguturikoak.


Kasualitatez, egun hauetan (baita urtarrilaren hasieran ere) ilberriaren fasetik gertu egon gara, gaur bertan (urtarrilak 30a) ilberria egonda. Eta ilberria egoteaz gain, aintzat hartu behar dugu Ilargiaren orbita pixka bat eliptikoa dela, zeinek inplikatzen duen momentu batzuetan, Ilargia Lurretik gertuago egongo dela (perigeo) eta beste batzuetan, aldiz, urrunago (apogeo). Gertutasun edo urruntasun horrek distantzietan % 13ko aldaketak eragingo ditu, mareak % 20an aeragotuz edo murriztuz.

Laburbilduz, egun hauetan koinziditu du, alde batetik, ilberria eta bestetik, Ilargia perigeotik gertuko kokapena. Hau gutxi balitz, borrasken ondorioz finkatu den eguraldi desegonkorrak mareen egoera areago okertu du. Beraz, badugu suntsipenak sortzeko gaitasun izugarri altua duen elementu ezberdinen konbinaketa bat. Zer falta zaigu gure nahasketa leherkorrean are suntsitzaileagoa izan dadin?

Itsasotik gertu ezarri den hiri bat, hain zuzen, aldaketa hauekiko oso sentikorra dena. Horixe da Donostiak jokatuko duen papera, beraz. Arrisku naturalen ikuspuntutik, arrisku bat agertzen da bakarrik gizakiak balizko mehatxu natural baten ondoan bere bizilekua eraikitzen duenean. Donostia itsasoari irabazitako lurretan hazi da eta bere paisaia esanguratsuenen artean, Kontxa, Haizearen Orrazia, Paseo Berria edo Kursaala egongo lirateke, eta guztiak itsasotik oso hurbil kokatzen dira. Horregatik, halako fenomenoak gertatzen direnean, itsasoak nolabait bere eremua eskatzen du bueltan, bidean aurkitzen dituen edozein azpiegitura deuseztatuz. Beste hitzetan esanda, Donostiaren kokapen ederrak koste bat dakar.

Orduan, zein da irakaspena? Muturreko gertakariak dira ala aldiz, nahiko ugariak diren eta baldintza naturalen menpe mugitzen diren fenomenoak? Aldaketa klimatikoak eraginik al du kasu honetan ala ekonomiak kontrolatutako hiritartze-prozesuei bota behar genieke errua? Noiz arte pairatu behar ditugu euren burua elite izendatzen dutenek gauzatutako akatsak, etekinak ateratzea helburu bakar dutenak?

Esaldi batek dioena apur bat aldatuz, "Gertakari baten interpretazioa aldatzen da segun eta ze kristaletik begiratzen duzun". Ba agian bada kristala aldatzeko garaia.

BIBLIOGRAFIA:

- COURSERA, 2013-2014. "Introduction to astronomy" izeneko irakasgaiaren apunteak.
- THE OPEN UNIVERSITY. 1999. Waves, tides and shallow-water processes, second edition, pp 50-88.

2013 was a year when I visited 3 countries: Iceland (where I lived until July), Basque Country (where I come from and where I live now) and Ecuador (where I spent the month of August). Therefore, the ranking is based on these three countries:

15. GAZTELUGATXE, BIZKAIA, BASQUE COUNTRY.


























14. REYNISFJARA, SUÐURLAND, ICELAND.


The south of Iceland contains lots of fantastic places inside, and one of them is this one, which combines several amazing elements. First of all, a black beach extending for some hundreds of metres and fused with a sea that turns fairly violent every once in a while. Furthermore, in the foreground of the picture, we can observe some columnar joints created when basalt cooled in the horizontal surface of the beach (columns develop perpendicular to the cooling surface). In this case, these features are quite big in size and allow visitors to go up a little bit (if you're careful enough). Then, if the tides are sufficiently low, one can walk around and discover a beautiful cave made of the same materials. A bit further on, as shown in the picture, there are two rock pinacles embedded in the sea witnessing the erosional power of the sea that grinded off a larger rocky body and left only these two elements. Finally, sometimes, one can spot one of the loveliest animals in the country: puffins (Fratercula arctica). I warmly recommend the area, especially because most of the visitors tend to stay in other parts of the region and forget this more hidden one.

13. VESTMANNAEYJAR ISLANDS, SUÐURLAND, ICELAND.



Off the Icelandic mainland, there is a group of islands that one can visit after travelling in a ferry for about 45 minutes. The island is really worth a visit, containing a relatively big population (in Icelandic terms) called Heimaey, built at the foot of the spectacular cliffs Heimaklettur. Besides that, we will find the Eldfell volcano (where the photograph was taken), from where a lava flow came down the slopes in 1973, swallowing the city it encountered as it was flowing ahead. Therefore, it is possible to see, at some points, how the lava broke some houses apart or was about to destroy other ones. Also, fluid lava flows from Helgafell (another volcano that is worth a hike) left some nice landforms in the centre of the island, which gradually change while approaching the sea, since water turns lava more explosive. I should not forget to mention the high probability of observing puffins (Fratercula arctica), given they lay their eggs in the southernmost area of the island, Stórhöfði.

12. GLJÚFRAFOSS, SUÐURLAND, ICELAND.




Hundreds of thousands of tourists visit the Seljanlandsfoss Waterfall, as it offers the unique possibility of walking behind it to see the waterfall from an interesting point of view. Yet the not-so-well-known Gljúfrafoss, a few tens of metres away, is usually skipped. The waterfall is as high as its neighbour but with smaller discharge; however, the location of this one is far more spectacular, confined in a small canyon and far from being overcrowded. A piece of advice is to stay in the rock on the right part of the picture and enjoy the view and the sound produced by this waterfall (but with waterproof clothes, please).

11. HVERIR GEOTHERMAL AREA, NORÐURLAND, ICELAND.




How can a country have temperatures ranging from -10ºC below zero (or colder) to 40ºC? The answer lies in geothermal areas, occupying vast areas of the country. In my opinion, the most astonishing geothermal area of the country is Hverir, in the North (Krafla system). Because of the abundance of some uncommon chemical elements (especially sulhpur), the colours of the area bring us mentally to extraterrestrial landscapes one could have never imagined. Among this steadily steaming area, I would like to underline mud pits (with mud continuosly sprouting) and the Namafjall fumarole seen in the background of the picture (there is a small mound emitting some gases). One pitfall: your nose will suffer a bit, as sulphur smell is quite intense in this site.

10. UREDERRA, NAFARROA, BASQUE COUNTRY.




One of the most unique natural wonders of the Basque Country is located at the foot of the Urbasa Mountain Range. Its name means "gorgeous water" and as soon as one sets foot on the area, the etymology will immediately be understood. Water is turquoise for the majority of the year, except during the rainy season in which water level rises significantly and acquires more whitish shades. The explanation for these colours comes from the materials the river encounters, which are rich in calcium carbonate (CaCO3), so water can filter through the formation and bring along some particular minerals with it that are responsible for tinting the water colour. There is a nice hike for around 1h30'-2h to get to the spot where the river is born; the visitor is rewarded with these hues of water throughout the entire trail. At the top, the visitor can observe the birth of the river by means of a small fall coming from the top, presumably where the water filtering through the permeable strata came across one impermeable stratum. At the top of the Urbasa Mountain Range, there is also a nice vantage point called "Balcón de Pilatos" (Pilate's Balconny), where the observer can admire the valley created by the river from the top, full of limestones containing small prints of moluscs and other small sea animals created when this area formed below the sea level and was subsequently brought up by tectonical forces.

9. ISLA DE LA PLATA, MANABÍ, ECUADOR.




8. JÖKULSÁRLÓN, AUSTURLAND, ICELAND.




In the souheast of the land of ice and fire, there is a wonderful glacial lagoon known as Jökulsárlón. The lagoon is created in front of the glacial tongue Breiðamerkurjökull, an outler glacier of Vatnajökull. With such a vast lake where the glacial tongue terminates, lots of icebergs are calved off the ice body and start floating on the water, where they move at the mercy of wind and water currents. Chunks of ice offer a nice view with a wide range of colours; from the pure white ice, to the more compressed blue ice and the black hues on account of debris eroded by the glacier or volcanic ash that fell on it. Seals (Halichoerus grypus) love the lagoon and occasionaly stick their head out of the water in order to breath. Furthermore, icebergs are just not moving across the lagoon, but also tend to completely reverse, thereby generating strong sounds that surprise the observer. One of the main advantages of the lagoon, to conclude, is the fact that it seasonally changes a lot, since thermal differences drive differential melting of the ice; therefore, visitors can come back over and over again without being bored with the same scenery.

7. ZUMAIA, GIPUZKOA, BASQUE COUNTRY.




Back in the Basque Coast, we have these interesting geological structures known as flysch and which abound along the entire coast. The strata were formed under water, and were subsequently lifted up by tectonics, which also bent them at some points, as we can see in the picture. On top of the structures, there is a chapel devoted to Saint Telmo and built probably at the 15th century, but was later restored and added some new features. Cliffs made of these strata terminating on a beach where sea erosion has carved some small caves are other interesting features. Finally, at low tide, one can see other strata lying horizontally (at the opposite side of the cliff in the picture, which is not shown) and will eventually find a stratum corresponding to the K-T limit, i.e. the period when the dinosaurs became extinct.

6. DETTIFOSS, NORÐURLAND, ICELAND.



Dettifoss is the biggest Icelandic waterfall and the one with highest discharge in Europe. Fitted into the canyon carved by the river Jökulsá á Fjöllum; the river managed to make it through large lava flows, presumably as a result of incredibly vast flooding episodes produced by a subglacial eruption or an eruption occurred under a glacier. Along the canyon, one can admire Selfoss, a smaller waterfall higher up in the river channel and shortly after comes this enormous beauty called Dettifoss. The sound produced by such a big amount of water falling onto the next step is amazing and is reflected in the water vapour coming up and which can give rise to big rainbows. In order for you to have a fairly good magnitude of the dimensions of the waterfall, there is a person on the left side of the picture next to the waterfall.

5. ÞÓRSMÖRK, SUÐURLAND, ICELAND.





4. CUICOCHA, IMBABURA, ECUADOR.




Cuicocha rewards the visitor with spectacular views of its nicely shaped lake surrounded by steep, circular slopes and containing two particular mounds inside (shown in the picture) separated by a small water channel. The formation of this complex is due to volcanic processes; some 3100 years ago, an extremely large eruption took place in the area, thus generating the collapse of the volcano into which is geologically termed a caldera. A subsequent eruption took place, but was not large enough and therefore, created these domes we can see as islands. Due to the appropriate environmental conditions, vegetation and some fauna rapidly colonised the small islets. Everyone is welcome to hike along the edges of the caldera for several hours, where he/she will also encounter very interesting cultural places; as the lake was used by the inca shamans for the practice of several rituals, there are some structures related to this culture that remain on the site.

3. WESTFJORDS, ICELAND.




The Westfjords in Iceland constitute a vast region, full of surprises for the tourist. Fjords are ancient valleys carved by glaciers when water level was lower than today, and later, sea level rose again and inundated these U-shaped valleys. Their cultural relevance can't be forgotten, let alone when Basque whalers had some contact with the locals and created a sort of Basque-Icelandic dictionary. The area itself is worth a visit, but there are spots that make it ever more beautiful. First of all, Dynjandi waterfall, which falls down into lots of steps belonging to different erupting episodes. Secondly, Rauðasandur Beach, is a place with reddish sand that makes it very special. Moreover, the cliffs in the Látrabjarg Peninsula are impressive, and from late spring until early autumn, there are lots of birds species at really close distances; among them, puffins (Fratercula arctica) and brunnish guillemots (Uria lomvia). Finally, nice fishing small towns spread across the area and the capital of the Westfjords Ísafjörður are also appealing.

2. COTOPAXI, COTOPAXI, ECUADOR.




If I needed to use two words in order to describe this wonder, I would use, symmetric magic. It is incredible how such a high mountain (5897 m) can be so symmetric and perfectly shaped. Its meaning in kichua is something like "Moon's neck" and it really conveys some beauty that could be compared to that of the Moon. As we can clearly see in the picture, it has a glacier above, whose dimensions are reducing more and more over time. Being a volcano under a glacier,  its eruptions are fairly dangerous, as they can create enormous flooding episodes like the ones commented for Dettifoss (no. 6), as well as columns of volcanic material that can collapse and flow downslope, thereby burning everything they find on their way. It is also a very nice place to observe bird species such as the carunculated caracara (Phalcoboenus carunculatus) or, if very lucky, the andine condor (Vultur gryphus). Finally, I would point out that when one is hiking the volcano, it is very likely to suffer from altitude sickness; in fact, at that height, oxygen is much lower and far more effort needs to be made to hike the same distance as at sea level. When you're walking that high, you get more tired, you feel as if  someone was putting extra pressure on your head, you need to concentrate on every step you give... This is true for at least, a not very experienced hiker.

1. LANDMANNALAUGAR, MIÐHÁLENDIÐ, ICELAND.




We end up the ranking travelling from a celestial landscape to an infernal landscape. And to my mind, there is nothing as infernal and as breathtaking as Landmannalaugar, located in the Icelandic highlands. Closed for tourists throughout most of the year, it exhibits an extremely wide range of colours one could hardly imagine. These colours appear in rhyolitic material, which is also a volcanic material that usually gives rise to yellowish-brownish shades, which can combine with white hues of the still remaining snow in early summer. All the area was created when the volcano Torfajökull erupted so largely that it collapsed (the same as Cuicocha, no. 4) and left a depression where a camping site has been set up. An obsidian lava flow, hikes to various peaks and an extensive natural hot top are waiting for you in this gorgeus area of incomparable beauty.

Landmannalaugar, I truly fell in love with you.

THE END!

p.d. Comments are appreciated: doubts, corrections, opinions about the ranking or the places...