ALBUFEIRA

O interesse incessante pelo regresso à infância:

- Páscoa tardia é culpa da Lua!

 Movimento de translação da Terra à volta do Sol

Este ano vivemos uma Páscoa invulgarmente tardia porque houve uma Lua cheia antes do equinócio da Primavera. Ora o que têm a ver o equinócio, a Lua e a Páscoa?

Em primeiro lugar, o equinócio da Primavera é o dia em que a Terra, na sua movimentação de 365 dias à volta do Sol, se alinha com ele de uma forma que o dia tem as mesmas horas de luz e de escuridão.

Esse movimento altera a inclinação dos raios solares em relação à Terra e as novas estações do ano começam, Primavera no hemisfério Norte e Outono no hemisfério Sul.

Ora, a Páscoa, que marca a ressurreição de Cristo e que é festejada na maior parte do mundo como um feriado católico, foi marcada em função da astronomia.

Quando em 325 d.C. um grupo de bispos cristãos de todo o mundo se juntou para definir os cânones e dogmas fundadores da Igreja Católica, ficou decidido que a ressurreição de Jesus Cristo deveria festejar-se no primeiro domingo depois da Lua Cheia que sobe no céu a seguir ao equinócio da Primavera.

Este ano, houve uma Lua Cheia a 19 de Março, ou seja, imediatamente antes do equinócio de dia 20 desse mês. Assim, a celebração da Páscoa atrasou-se até à Lua Cheia seguinte, que só chegou no início desta semana, a 16 de Abril.

(A partir de notícia do Jornal Público)

Mister S. Spock

Mister S. Spock foi leiloado no site leilões.net, por uma quantia deveras aliciante para o estado português, tomando em consideração o estado das nossas finanças e a presença do FMI em Portugal.

Nele se informava o público interessado, da possibilidade de pagamento do produto em transferência bancária e com a vantagem da entrega contemplar portes grátis, facto deveras importante, nesta época de crise.

Elucidativa no seu objectivo, esta transacção apresentava-se muito bem suportada em conhecimentos pessoais e técnicos, do dito produto em trânsito.

Boa aparência, guarda-fatos e teleponto incluído, excelente marketeer, desenrascado, persistente e com boa imagem de lado, licenciado ao domingo, falando Castelhano e Inglês, boa rede de contactos com políticos e amigos, muitos amigos

Agora percebo porque é que a venda deste produto foi imediatamente anulada, desaparecendo de uma forma fulminante, do campo de acção da rede: a sua influência era brutal e para além do mais, já tinha sido comprado e já estava hipotecado!

New subduction zone may increase quake risk in the Mediterranean, expert says

The Mediterranean Sea stretches eastward from the Strait of Gibraltar in a 1994 astronaut photograph.

Europe may be starting to dive under Africa, creating a new subduction zone and potentially increasing the earthquake risk in the western Mediterranean Sea, scientists report.

Subduction zones form where tectonic plates collide, with one plate diving beneath the other and into Earth's mantle. Sometimes these collisions are gradual, but often they occur in big lurches that can trigger quakes.

Because subduction zones are generally on seabeds, earthquakes in these zones can set off tsunamis, like the killer wave that devastated Japan last month.

For millions of years the African plate, which contains part of the Mediterranean seabed, has been moving northward toward the Eurasian Plate at a rate of about an inch every 2.5 years (a centimeter a year).

Now studies of recent earthquakes in the region indicate that a new subduction zone may be forming where the plates are colliding along the coasts of Algeria and northern Sicily (see a map of the region).

"Formation of a new subduction zone is very rare," said study leader Rinus Wortel, a geophysicist at Utrecht University in the Netherlands.

Europe and Africa Switching Geologic Roles

You can see from this picture of the earth plates that the largest plates are under Africa and Europe

According to Wortel, the opposite situation existed about 30 million years ago, when the African plate was diving under the Eurasian plate along a sizable subduction zone in the western Mediterranean.

There, the dense rocks of the African seabed were being thrust beneath the European plate.

Over millions of years, Africa moved so far north that none of the plate's seabed was left in the western Mediterranean. All that remained were the rocks of the continent itself, which were lighter than the seabed and wouldn't subduct, Wortel said.

But the two plates have continued to converge, building up tectonic stresses. Part of this stress was taken up by the buckling of the Eurasian plate into the Alps, Caucasus, and Zagros mountain ranges. (Related: "Alps Glaciers Gone by 2050, Expert Says.")

Now, based on the locations and motions of recent earthquakes along the plate borders, Wortel and colleagues think subduction is starting up again—but this time with Europe being thrust under Africa.

The new subduction zone, announced at a recent meeting of the European Geosciences Union in Vienna, is an exciting find, Wortel said, because such regions tend to exist for long time periods, geologically speaking.

Earthquake Risk Underestimated in the Med?

Last 24h: Euro-Med earthquakes

Other scientists are intrigued by the possible subduction zone—but they remain cautious.

"I didn't hear the talk, but it's perfectly plausible," Seth Stein, a geophysics professor at Northwestern University in Evanston, Illinois, said in an email. For instance, other parts of the Mediterranean region—such as mainland Italy—have seen tectonic changes in the past two million years, he said.

Still, deciphering these changes is a very complex process, said Chris Goldfinger, director of the Active Tectonics and Seafloor Mapping Laboratory at Oregon State University in Corvallis.

"I'd have to spend a week with the data to have any opinion that was worth anything," he said by email.

Study leader Wortel added that the formation of a subduction zone is a slow process: "These processes happen at the time scale of several million years," he said.

For example, he said, most established subduction zones are marked by giant undersea trenches. A similar trench should eventually form in the Mediterranean—but certainly not overnight.

Wortel does believe that the new data may mean the earthquake risk in the western Mediterranean has been underestimated—and may be increasing. (See related pictures of the aftermath of a magnitude 6 earthquake in Italy in 2009.)

"It is usually not considered to be a region of enormous seismic activity—not of the giant magnitude we experienced in Japan last month," Wortel said.

That may simply be due to historical complacency. "Even though something has not occurred in a hundred years, it does not mean there is no risk."

In fact, he noted, 70,000 people were killed in Messina, Italy, in 1908 when a magnitude 7.1 earthquake produced a tsunami with waves reported at 40 feet (12 meters) high.

And one of the most devastating earthquakes in European history occurred somewhere west of the Strait of Gibraltar in 1755, sending a giant wave into Lisbon, Portugal, and killing—by some estimates—as many as a hundred thousand people.

Portugal

1755 Lisbon earthquake

The estimated magnitude of 8.7 makes the 1755 earthquake 20 times stronger than the 1906 San Francisco earthquake.

It generated a 5- to 10-meter-high (16- to 33-foot-high) tsunami wave, which swept across the coasts of Spain, southern Portugal and Morocco, devastating most of the ports and dragging people and debris out to sea.

Shaking was felt in France, Italy, and North Africa. The quake was reported to have lasted for as long as ten minutes.

The disaster was a setback to a powerful trading nation—Lisbon may have been the richest city in Europe at the time—and caused an important shift in the balance of power of the era.

Text – National Geographic