The volcanic eruption in Iceland, which began on Wednesday, is just such a reminder. As ash spews out across northern Europe, grounding all flights across Scandinavia and the UK, we begin to realise how powerless we humans are. But as volcanic eruptions go, the current fireworks on Iceland are small fry.

Scientists rank volcanoes according to how explosive they are, using the volcanic explosivity index (VEI), which goes from zero to eight. The measurement is based on how much material is thrown out of the volcano, how high the eruption goes and how long it lasts. Like the scale used to measure earthquake size, the VEI is logarithmic - meaning that a volcano with a VEI of five is 10 times more powerful than one with a VEI of four.

To volcanologists, Iceland is heaven. There are 30 active volcanic systems on the island and very frequent firework displays. Geologists believe that the reason for Iceland's explosive nature is because it sits over a "mantle plume" - a rising column of abnormally hot molten rock, originating at the edge of the Earth's core.

To make matters even more spectacular, this particular mantle plume has positioned itself under the mid-Atlantic ridge: the crack that runs down the middle of the Atlantic, where the ocean floor divides and continuously spews out fresh lava.

The US, however, is not happy with the Syrian transfer of missiles to Lebanon - and an expert says Israel will have to take action.

Profssor Eyal Zisser, head of the Dayan Center for Middle Eastern Studies in Tel Aviv University, told Arutz-7 that the news requires Israel to make some difficult decisions. "There's no question that the transfer of [these missiles] is an escalation," Zisser said. "These Scuds are more precise than those that Saddam Hussein launched at us in the Gulf War of 1991, and they have a longer range as well."

White House spokesman Robert Gibbs said the US has relayed its concern to the Syrian government, Senator John McCain raised the issue at the hearing on Iran on Wednesday, and Under Secretary of Defense Flournoy said the US is "very concerned" by these reports.

His comment drew a stern rebuke from his former rival in the presidential campaign. Obama was responding to a question Tuesday about how the summit would play into peace-making efforts in the Middle East when he addressed the downsides of - by virtue of America's world stature - being obligated to intervene in international conflicts.

"It is a vital national security interest of the United States to reduce these conflicts because whether we like it or not, we remain a dominant military superpower, and when conflicts break out, one way or another we get pulled into them," Obama said. "And that ends up costing us significantly in terms of both blood and treasure."

The remark got little attention in mainstream coverage of the summit, but was picked up on several conservative blogs, which panned the president for suggesting Americans had grown weary of superpower status.

"I understand that many may disagree with that conclusion and some may even view it as a criticism of prayer or those who pray," Crabb said in her opinion. "That is unfortunate. A determination that the government may not endorse a religious message is not a determination that the message itself is harmful, unimportant or undeserving of dissemination."

The opinion comes in a case filed by the Freedom From Religion Foundation, a Wisconsin-based group of self-described "atheists" and "agnostics." Crabb said her ruling is based on "relevant case law," and it does not prevent religious groups from organizing prayer services or prevent the President from discussing his views on prayer. "The only issue decided in this case is that the federal government may not endorse prayer in a statute," Crabb said.

On the holiday last year, President Obama issued a statement saying Americans have always "come together in moments of great challenge and uncertainty to humble themselves in prayer."

"In 1775, as the Continental Congress began the task of forging a new Nation, colonists were asked to observe a day of quiet humiliation and prayer," the statement said. "Almost a century later, as the flames of the Civil War burned from north to south, President Lincoln and the Congress once again asked the American people to pray as the fate of their Nation hung in the balance."

When Mr Obama declared that resolving the long-running Middle East dispute was a "vital national security interest of the United States," he was highlighting a change that has resulted from a lengthy debate among his top officials over how best to balance support for Israel against other American interests.

This shift, described by administration officials who did not want to be quoted by name when discussing internal discussions, is driving the White House's urgency to help broker a Middle East peace deal. It increases the likelihood that Mr Obama, frustrated by the inability of the Israelis and the Palestinians to come to terms, will offer his own proposed parameters for an eventual Palestinian state.

Mr Obama said conflicts like the one in the Middle East ended up "costing us significantly in terms of both blood and treasure" - drawing an explicit link between the Israeli-Palestinian strife and the safety of American soldiers as they battle Islamic extremism and terrorism in Iraq, Afghanistan and elsewhere.

Mr Obama's words reverberated through diplomatic circles in large part because they echoed those of General David H Petraeus, the military commander overseeing America's wars in Iraq and Afghanistan. In recent Congressional testimony, the general said that the lack of progress in the Middle East created a hostile environment for the United States. He has denied reports that he was suggesting that soldiers were being put in harm's way by American support for Israel.

The king, in Washington for President Barack Obama's nuclear summit, gave his warning after Israel claimed that Syria had handed over Scud missiles in its armoury to the Lebanon-based Hizbollah. His comments, which were made to a private meeting of the US Congressional Friends of Jordan caucus were said to be "sobering".

Syria yesterday denied the allegation that it has provided Hizbollah with long-range Scud missiles, which would allow them to target Israel's cities. The country's foreign ministry said the claims would be used as a pretext by Israel to raise tension prior to a possible attack on Hizbollah.

"For some time now, Israel has been running a campaign claiming that Syria has been supplying Hizbollah with Scud missiles in Lebanon," a foreign ministry statement released yesterday said. "Syria strongly denies these allegations which are an attempt by Israel to raise tensions in the region."

However, the statement did not appear to rule out an alternative possibility being raised by defence sources, that Damascus has allowed Hizbollah control of or access to Scud missiles still currently in Syria. Officials in Syria have warned that it would join in any war involving Israel, Lebanon and Hizbollah.

After a series of crushing earthquakes in the early hours of Wednesday morning, the largest being recorded by the Chinese Earthquake Administration at magnitude 7.1, a four-storey shopping centrecomplex collapsed and caught fire, incinerating most of its occupants.

Elsewhere in Jiegu, the death toll had reached 617 on Thursday, with a further 9,110 injured, 1,000 seriously. Among the dead were 66 children from three local schools. Makeshift hospitals had been set up, but medicine was still in transit on Thursday and doctors told the Chinese state media there was little they could do other than amputate.

Jiegu lies on the Tibetan plateau, more than 12 hours from the nearest major airport, but China immediately mobilised the full might of its resources, summoning rescue workers from across the country.

President Obama told delegates from 47 nations at the Nuclear Security Summit on Tuesday that it would be a "catastrophe for the world" if al-Qaeda or another terrorist group got a nuclear device, because so many lives would be lost and it would be so hard to mitigate damage from the blast.

A 10-kiloton nuclear explosion would level buildings within half a mile of ground zero, generate 900-mph winds, bathe the landscape with radiation and produce a plume of fallout that would drift for hundreds of miles, the guide says. It was posted on the Internet and sent to local officials.

The document is designed to help local officials craft plans for responding to a nuclear blast. The prospect is anything but far-fetched, says Rick Nelson of the Center for Strategic and International Studies. "Do I think in my lifetime I'll see the detonation of a nuclear device? I do."

The man who 'broke' the Bank of England (and who is still able to earn a cool $3.3 billion in a year) said the same strategy of borrowing and spending that had got us out of the Asian crisis could shunt us towards another crisis unless tough lessons are learned.

Soros, who worked as a porter to pay for his studies at the London School of Economics after emigrating from Hungary, warned us to heed the lesson that modern economics had got it wrong and that markets are not inherently stable.

"The success in bailing out the system on the previous occasion led to a superbubble, except that in 2008 we used the same methods," he told a meeting hosted by The Economist at the City of London's modern and impressive Haberdashers' Hall. "Unless we learn the lessons, that markets are inherently unstable and that stability needs to the objective of public policy, we are facing a yet larger bubble."

"We have added to the leverage by replacing private credit with sovereign credit and increasing national debt by a significant amount."

Up to 5,000 flights could have been affected by the end of Thursday. Planes have been grounded in the UK, Ireland, the Netherlands, Belgium, Denmark, Norway, Sweden and Finland. France is also preparing to close its main airports. Eurocontrol, which covers 38 nations across Europe, said the ash ejected by the volcano underneath the Eyjafjallajoekull glacier in Iceland would continue to move in a south-easterly direction.

Experts have warned that the tiny particles of rock, glass and sand contained in the ash cloud could be sufficient to jam aircraft engines. Mr Flynn, Eurocontrol's assistant head of operations, said the extent of the disruption was "greater than we've ever seen before in the EU" and warned that the problem could persist for a further 48 hours.

"The meteorological situation is such that the volcanic ash is progressing very slowly eastwards but there is not a lot of wind... so it is very slow and very dense," he told the Reuters news agency.

The restrictions silenced Heathrow airport, the world's second busiest, and stranded tens of thousands of passengers around the world. Norway, Denmark, Sweden, Belgium and the Netherlands all later shut down their airspace entirely, while there was also major disruption in Finland, France, Germany and Spain.

"We will review further Met Office information, and at 0230 BST tomorrow we will advise the arrangements that will be in place through to 1800 BST tomorrow. However, be aware that the situation cannot be said to be improving with any certainty as the forecast affected area appears to be closing in from east to west. We continue to work closely with airports, airlines, and the rest of Europe to understand and mitigate the implications of the volcanic eruption."

The statement from the Israeli prime minister's anti-terror office took the unusual step of calling on families of Israelis visiting the Sinai to establish contact with them.

The commander of the anti-terror office, Brigadier General Nitzan Nuriel, acknowledged that there had been rumors that Israelis have been kidnapped in the Sinai. "We don't work according to rumors," he Israel TV. "We work according to firm intelligence." He said it would "take some time" to disprove the rumors, which circulated all day Tuesday.

"It is very possible that at this moment, there is a terror cell that has the intention and has a plan in operation to kidnap an Israeli and bring him to Gaza," he said. Palestinian militants in Gaza have been holding an Israeli soldier captive for more than three years. In unusually strong wording, the Israeli anti-terror office called "on all Israelis residing in Sinai to leave immediately and return home. Families of Israelis residing in Sinai are asked to contact them and update them on the travel warning."

And their alleged plan ended in disaster when the Polish pilots made one final and disastrous attempt to land, killing Mr Kaczynski, his wife, and 94 others on board the plane. 'One version of events says that the plane approached the airport four times, because every time the Russians refused it permission to land - they wanted to send the plane with the president to an airport in Moscow or Minsk,' Mr Gorski claimed in an interview published in the newspaper Nasz Dziennik.

'They came up with some dubious reasons: that there was fog over the airport, and that the navigation system didn't work as it was under renovation, and that airport had a short landing strip.' The claims were made as shocking new details emerged of the final minutes of the flight before it crashed into a Russian forest on Saturday morning. One of the Russian air traffic controllers involved in the tragedy said he believes the Polish air force pilot Arkadiusz Protasiuk, 36, was under severe pressure 'to land at any cost' so that the president would not miss the commemoration of the death of 22,000 Poles slaughtered by Stalin.

But he claims there were also serious language problems between the control tower at the military airport near Smolensk and the crew as the aircraft began its descent, and final approach, 'without our permission'. The crew failed to report to the ground their altitude readings, said Colonel Anatoly Muraviev, a former pilot. He believes the captain 'was desperate to land because of the high ranking passengers he was carrying. It killed both the crew and the passengers.'

It was known that Mr Kaczynski once fired a flight crew when they refused to land at Tbilisi - and flew to another airport, he said. 'Now try to imagine yourself in chief pilot's shoes. Fear, false shame, thinking that going to another airport is a disgrace - all this led to the fact that the crew died and killed all the others. I am a former pilot myself, I understand all this very well.'

Cardinal Tarcisio Bertone had said homosexuality, not celibacy, lay behind the child sex abuse scandals. The cardinal, the Vatican's foreign minister, was speaking in Chile, where his comments were also condemned. Cardinal Bertone was attempting to defuse the scandals currently afflicting the Catholic Church, which are largely cases of priests molesting children, mainly boys, the BBC's David Willey reports from Rome. He added that some "surprising" initiatives regarding the sex abuse scandal would soon be revealed but did not elaborate.

Visiting the Chilean capital Santiago on Monday, Cardinal Bertone told a news conference: "Many psychologists, many psychiatrists have demonstrated that there is no relationship between celibacy and paedophilia but many others have demonstrated, I was told recently, that there is a relationship between homosexuality and paedophilia. That is true. I have the documents of the psychologists. That is the problem."

A Chilean communist MP, Hugo Gutierrez, told AFP news agency: "Celibacy does more damage to a human being than homosexuality, which is a freely made choice. I'm shocked by these words from a senior dignitary of the Church." Aurelio Mancuso, former president of a Italian gay rights association Arcigay, said: "The truth is that Bertone is clumsily trying to shift attention to homosexuality and away from the focus on new crimes against children that emerge every day."

Chinese TV showed wrecked buildings and people scrabbling through debris, as the government began a rescue misssion. Yushu is hundreds of miles from an airport, and it is thought rescue crews may take time to reach the quake zone. "Soldiers have been dispatched to save the people buried in the collapsed houses," local official Huang Limin was quoted as saying by China's state news agency Xinhua.

The region, which is home to ethnic Mongolians and Tibetan farmers and herdsmen, is dotted with coal, tin, lead and copper mines. China's Sichuan province, which neighbours Qinghai, suffered a huge earthquake in 2008, when thousands of schoolchildren were among the 87,000 people killed or missing. Five million people also lost their homes, and officials estimated rebuilding work would take at least three years.