'Polar Wander:' Earth's Outer Layers May Be Drifting Over Molten Core

By: Charles Q. Choi, OurAmazingPlanet Contributor
Published: 10/08/2012 12:35 PM EDT on OurAmazingPlanet

The entire outermost part of Earth may be wandering over the planet's whirling molten core, new research suggests.

Knowing whether the Earth's outer layers are roaming in this manner is key to understanding the big picture of how the planet's surface is evolving overall, scientists added.

At various times in Earth's history, the planet's solid exterior — its crust and mantle layers — has apparently drifted over the planet's spinning core. To picture this, imagine that a peach's flesh somehow became detached from a peach's pit and was free to move about over it.

This movement of the Earth's outer layers is known as "true polar wander." It differs from the motion of the individual tectonic plates making up Earth's crust, known as tectonic drift, or the motions of Earth's magnetic pole, called apparent polar wander.

'Hot spot' landmarks

Past research suggested the Earth experienced true polar wander during the early Cretaceous period that lasted from 100 million to 120 million years ago. Determining when, in which direction and at what rate true polar wander is taking place depends on having stable landmarks against which one can observe the motion of Earth's outer shell, much like one can tell a cloud is moving by seeing if its position has changed relative to its surroundings.

Volcanic "hot spots," or areas of recurrent volcanism, are one potential landmark. Geologists have suggested these are created by mantle plumes, giant jets of hot rock buoying straight upward from near the Earth's core. Mantle plumes are thought to create long island chains such as the Hawaiian Islands as they sear tectonic plates drifting overhead.

Scientists have treated hot spots as stationary features for decades. The idea was that material surrounding the mantle plumes roil about to form structures known as convection cells that kept the plumes straight and fixed in place. [50 Amazing Volcano Facts]

Later on, however, researchers began suggesting that mantle plumes could move about slightly, caught as they are in the flowing mantle layer under the crust. "From this point of view, the plumes are expected to move, bend and get distorted by the 'mantle wind,' resulting in hot spot drift over geologic time," said researcher Pavel Doubrovine, a geophysicist at the University of Oslo in Norway.

By allowing hot spot positions to meander slowly, Doubrovine and his colleagues have devised computer simulations that better match observations of the chains of islands created by each hot spot.

"Estimating hot spot drift in the geological past is not a trivial task," Doubrovine told OurAmazingPlanet. "It requires substantial modeling efforts."

The scientists then compared the way the Earth's outermost layers drifted in relation to the planet's axis of spin. The Earth's magnetic field is aligned with the core's axis of rotation, and researchers can tell how Earth's magnetic field was oriented in the past by analyzing ancient rock. Magnetic minerals in molten rock can behave like compasses, aligning with Earth's magnetic field lines, an orientation that gets frozen in place once the rock solidifies.

Current wandering

Using their simulations and the magnetic field rock record, the scientists identified three new potential instances of true polar wander over the past 90 million years. These include two cases in which the Earth's solid outermost layers traveled back and forth by nearly 9 degrees off Earth's axis of spin from 40 million to 90 million years ago. Moreover, the researchers suggest that Earth's outer shell has been undergoing true polar wander for the past 40 million years, slowly rotating at a rate of 0.2 degrees every million years.

Researchers suspect true polar wander is caused by shifting of matter within the mantle, due, for instance, to variations in temperature and composition. However, "we don't know yet what specific tectonic events may have triggered the specific episodes of true polar wander that we identified," Doubrovine said.

These new details regarding true polar wander could help shed light on what triggers it. In the future, the researchers plan to look even further in the past at how the planet's outermost layers have changed. Doubrovine and his colleagues Bernhard Steinberger and Trond Torsvik detailed their findings online Sept. 11 in the Journal of Geophysical Research — Solid Earth.

from: Huffington Post

Mount Lokon spews ash clouds in seventh eruption since Sept

ONE of Indonesia's most active volcanoes has erupted again, spewing clouds of ash, an official has said. 
 

News.com - The 1580 metre (5,214 feet) Mount Lokon on northeast Sulawesi island erupted at 2pm local time on Sunday with thunderous sounds heard as far as five kilometres away.

"Lokon has been quite active the past few months. This was the seventh biggest eruption since mid-September," government vulcanologist Farid Bina told AFP from the volcano's monitoring post in North Sulawesi province.

"It produced a loud sound like thunder. But we cannot detect the height of the eruption as thick clouds covered its peak," he said, adding that muddy rains fell in surrounding areas.

There was no plan to upgrade the volcano's alert level despite the series of eruptions, he said, adding that the nearest village of 250 people was outside the 2.5 kilometre danger zone.

The volcano experienced its biggest recent eruption in July 2011, when more than 5200 people were evacuated as it sent huge clouds of ash as high as 3500 metres into the sky.

Since then Mount Lokon has erupted and spewed clouds of ash about 600 times.

The volcano's last deadly eruption was in 1991, when it killed a Swiss tourist.

The Indonesian archipelago has dozens of active volcanoes and straddles major tectonic fault lines known as the "Ring of Fire" between the Pacific and Indian oceans.

The country's most active volcano, Mount Merapi in central Java, killed more than 350 people in a series of violent eruptions last year.

Fuse lit in Middle East: Escalation of tensions in Gaza, clashes intensify between Syria and Turkey

October 8, 2012 – ISRAEL – Israeli warplanes responded immediately, striking a number of rocket-launching squads as they fired toward Israel, according to the military, and hitting several facilities belonging to Hamas, the Islamic group that controls Gaza, which the military said were being used to store weapons. Ashraf al-Qedra, a spokesman for the Health Ministry in Gaza, said that five Palestinians were injured in Monday’s strikes, one of them seriously. The latest flare-up began with the missile strike on Sunday against two men who Israel said were members of jihadist groups involved in terrorist activity against Israel. Some Palestinian news outlets identified the two men as members of radical Salafist groups. Gaza medical officials said that the two, who were struck while riding on a motorcycle, were critically wounded, and that at least eight passers-by were also injured. A spokeswoman for the Israeli military said that up to 30 mortar shells had fallen inside Israel on Monday morning, and the military said that a number of rockets also struck Israeli territory near the Gaza border. The armed wings of Hamas and Islamic Jihad, a smaller militant group, claimed responsibility for the rocket and mortar fire, saying that they were aiming at Israeli military bases near the border. A spokesman for the military wing of Hamas, known only by his nom de guerre, Abu Obeida, said that Monday’s attacks were meant as “a message” that “the Palestinian resistance will not allow unilateral aggression” from Israel. He warned of “stronger, expanded responses” if the Israeli raids continued. Most of the rockets and mortars fell in uninhabited areas in Israel, but the military said that some buildings were damaged. Several goats were killed in a petting zoo in an Israeli communal farm near the border, according to the news Web site Ynet. Israelis were marking the last day of the Sukkot holiday on Monday, and schools and offices were closed. Israelis near the Gaza border were advised to remain close to bomb shelters and protected areas. The Education Ministry in Gaza said that four schools in southeast Gaza were evacuated because of Israeli shelling in the area. Hamas has largely adhered to an informal, if fragile, cease-fire with Israel and has acted in the past to rein in smaller groups, but this was the second time in less than four months that Hamas joined in firing rockets at Israel. –NY Times

 (Reuters) - Turkish President Abdullah Gul said on Monday the "worst-case scenarios" were now playing out in Syria and Turkey would do everything necessary to protect itself, as its army fired back for a sixth day after a shell from Syria flew over the border.
Gul said the violence in Turkey's southern neighbor, where a revolt against President Bashar al-Assad has evolved into a civil war that threatens to draw in regional powers, could not go on indefinitely and Assad's fall was inevitable.
"The worst-case scenarios are taking place right now in Syria ... Our government is in constant consultation with the Turkish military. Whatever is needed is being done immediately as you see, and it will continue to be done," Gul said.
"There will be a change, a transition sooner or later ... It is a must for the international community to take effective action before Syria turns into a bigger wreck and further blood is shed, that is our main wish," he told reporters in Ankara.

Turkey's armed forces have bolstered their presence along the 900-km (560-mile) border with Syria in recent days and have been responding in kind to gunfire and shelling spilling across from the south, where Assad's forces have been battling rebels who control swathes of territory.
Turkey's Chief of Staff, General Necdet Ozel, travelled to the southern city of Adana to inspect the region patrolled by Turkey's 2nd Army, which protects the border with Syria, the military said on its website.

U.N. Secretary-General Ban Ki-moon said the escalation of the conflict along the Turkey-Syria border, as well as the impact of the crisis on Lebanon, were "extremely dangerous".
"The situation in Syria has dramatically worsened. It is posing serious risks to the stability of Syria's neighbors and the entire region," he told a conference in Strasbourg, France.
Ban said U.N. and Arab League envoy Lakhdar Brahimi would be heading back to the region this week.

MILITARY MOVEMENTS
The exchanges with Turkey mark the most serious cross-border violence in Syria's revolt against Assad, which began in March last year with peaceful protests for reform and has evolved into a civil war with sectarian overtones.

"From now on, every attack on us will be responded to immediately. Every attack that targets our sovereignty, our security of life and property will find its response," Turkish government spokesman Bulent Arinc said after a cabinet meeting.

Parliament last week authorized the deployment of Turkish troops beyond its borders although government officials said the move was meant as a deterrent rather than a "war mandate".
"Turkey will decide itself when the situation necessitates acts mentioned in the motion the parliament passed last week. Nobody should think war will follow a parliament approval ... but we are more sensitive about our independence and sovereignty than most countries," Arinc said.

Turkey's Dogan news agency said some 25 warplanes had been sent to a military base in Diyarbakir, the largest city in the southeast, and reported military sources as saying this was in connection with Syria and cross-border anti-terror operations.

It said a large number of F-16 fighter planes landed at the base on Monday afternoon. Local sources confirmed there was heightened activity at the base but said this was related to operations against Kurdish militant bases in northern Iraq, not Syria.

Separately, a convoy of military vehicles, including tanks loaded on trucks, travelled to the town of Akcakale on Monday to be deployed on the border, Dogan reported.
Fighting further inside Syria also intensified on Monday.

Syrian government forces advanced for the first time in months into the rebel-held Khalidiya district in the besieged central city of Homs.

"They have occupied buildings that we were stationed in and we had to evacuate," a rebel fighter told Reuters by Skype.

Skirmishes on the Syrian side of the border have been escalating and it is unclear who fired the shells that have crossed into Turkey.

Damascus has said it fired into Turkey accidentally, but has failed to live up to pledges made last week, after a Syrian shell killed five civilians in Akcakale, to ensure no more ordnance flies across the border.

Turkey launched its latest retaliatory strike on Monday after a mortar bomb fired from Syria landed in countryside in the Turkish province of Hatay some 150-200 m (yards) inside the district of Hacipasa, a Turkish official told Reuters.

TRUCKS PATROLLING
Further east, Syrian rebel sources in Raqqa province, which borders Akcakale, said they had seen five Turkish army trucks full of soldiers patrolling the border.

NATO member Turkey was once an ally of Assad's but turned against him after his violent response to the uprising, in which activists say 30,000 people have died.

Turkey has nearly 100,000 Syrian refugees in camps on its territory, has given sanctuary to rebel leaders and has led calls for Assad to quit. Its armed forces are far larger than Syria's.
Turkish Foreign Minister Ahmet Davutoglu said at the weekend that a potential leader in an interim Syrian government could be Vice-President Farouq al-Shara.

Reports in August said Shara, a former foreign minister who was appointed vice president six years ago, had tried to defect to neighboring Jordan, but Syrian state media subsequently said he had never considered leaving.

"The opposition is inclined to accept these names. Farouq al-Shara has the ability to understand the system of the last 20 to 30 years," Davutoglu told the state broadcaster TRT.
"Farouq al-Shara did not get involved in the recent incidents, the massacre, in a very wise and conscientious attitude. But perhaps there is nobody who knows the system better than al-Shara."

(Reporting by John Irish in Paris, Mert Ozkan in Ankara, Daren Butler in Istanbul and Mariam Karouny in Beirut; Writing by Nick Tattersall; Editing by Michael Roddy)