Strong 6.8-Magnitude Earthquake Hits Western Brazil

A strong earthquake with a preliminary magnitude of 6.8 has struck Brazil’s Amazon region, but damage is unlikely because it struck at a depth of nearly 600 kilometers (372 miles), seismologists say.

The earthquake, which struck at 2:25 p.m. local time on Saturday, was centered in the Amazon rainforest, about 89 kilometers (55 miles) west of Tarauacá in Acre state, or 739 kilometers (459 miles) northeast of Lima.

The U.S. Geological Survey measured the magnitude at 6.8 but said it struck at a depth of 575 kilometers (479 miles), making it a very deep earthquake. Peru’s seismological agency put the magnitude significantly higher, at 7.2.

Damage is unlikely because it struck far below the surface and in a remote area. Computer models from the UN estimate that nearly 5,300 people live within 50 kilometers (31 miles) of the earthquake epicenter.

Saturday’s earthquake was the strongest to hit Brazil since 2003, when a powerful 7.1-magnitude earthquake hit the same region. However, strong and deep earthquakes sometimes hit Peru in areas that are close to the border with western Brazil. They rarely cause damage.

How Climate Change Caused the World’s First Empire to Collapse

Not one smoke stack, vehicle, or petroleum of any form was mentioned in this scientific article. However, there does appear to be an assumption of rhythmic cycles.

Gol-e-Zard Cave lies in the shadow of Mount Damavand, which at more than 5,000 meters dominates the landscape of northern Iran. In this cave, stalagmites and stalactites are growing slowly over millennia and preserve in them clues about past climate events. Changes in stalagmite chemistry from this cave have now linked the collapse of the Akkadian Empire to climate changes more than 4,000 years ago.

Akkadia was the world’s first empire. It was established in Mesopotamia around 4,300 years ago after its ruler, Sargon of Akkad, united a series of independent city states. Akkadian influence spanned along the Tigris and Euphrates rivers from what is now southern Iraq, through to Syria and Turkey. The north-south extent of the empire meant that it covered regions with different climates, ranging from fertile lands in the north which were highly dependent on rainfall (one of Asia’s “bread baskets”), to the irrigation-fed alluvial plains to the south.

It appears that the empire became increasingly dependent on the productivity of the northern lands and used the grains sourced from this region to feed the army and redistribute the food supplies to key supporters. Then, about a century after its formation, the Akkadian Empire suddenly collapsed, followed by mass migration and conflicts. The anguish of the era is perfectly captured in the ancient Curse of Akkad text, which describes a period of turmoil with water and food shortages: “… the large arable tracts yielded no grain, the inundated fields yielded no fish, the irrigated orchards yielded no syrup or wine, the thick clouds did not rain.”

Drought and dust

The reason for this collapse is still debated by historians, archaeologists and scientists. One of the most prominent views, championed by Yale archaeologist Harvey Weiss (who built on earlier ideas by Ellsworth Huntington), is that it was caused by an abrupt onset of drought conditions which severely affected the productive northern regions of the empire.

Weiss and his colleagues discovered evidence in northern Syria that this once prosperous region was suddenly abandoned around 4,200 years ago, as indicated by a lack of pottery and other archaeological remains. Instead, the rich soils of earlier periods were replaced by large amounts of wind-blown dust and sand, suggesting the onset of drought conditions. Subsequently, marine cores from the Gulf of Oman and the Red Sea which linked the input of dust into the sea to distant sources in Mesopotamia, provided further evidence of a regional drought at the time.

Many other researchers viewed Weiss’s interpretation with skepticism, however. Some argued, for example, that the archaeological and marine evidence was not accurate enough to demonstrate a robust correlation between drought and societal change in Mesopotamia.

A new detailed climate record

Now, stalagmite data from Iran sheds new light on the controversy. In a study published in the journal PNAS, led by Oxford palaeoclimatologist Stacy Carolin, colleagues and I provide a very well dated and high resolution record of dust activity between 5,200 and 3,700 years ago. And cave dust from Iran can tell us a surprising amount about climate history elsewhere.

Gol-e-Zard Cave might be several hundred miles to the east of the former Akkadian Empire, but it is directly downwind. As a result, around 90% of the region’s dust originates in the deserts of Syria and Iraq.

That desert dust has a higher concentration of magnesium than the local limestone which forms most of Gol-e-Zard’s stalagmites (the ones which grow upwards from the cave floor). Therefore, the amount of magnesium in the Gol-e-Zard stalagmites can be used as an indicator of dustiness at the surface, with higher magnesium concentrations indicating dustier periods, and by extension drier conditions.

The stalagmites have the additional advantage that they can be dated very precisely using uranium-thorium chronology. Combining these methods, our new study provides a detailed history of dustiness in the area, and identifies two major drought periods which started 4,510 and 4,260 years ago, and lasted 110 and 290 years respectively. The latter event occurs precisely at the time of the Akkadian Empire’s collapse and provides a strong argument that climate change was at least in part responsible.

The collapse was followed by mass migration from north to south which was met with resistance by the local populations. A 180km wall – the “Repeller of the Amorites” – was even built between the Tigris and Euphrates in an effort to control immigration, not unlike some strategies proposed today. The stories of abrupt climate change in the Middle East therefore echo over millennia to the present day.

JUST IN: Researchers Find Deep Ocean Getting Colder

A pair of researchers, one with the Woods Hole Oceanographic Institution, the other Harvard University, has found evidence of deep ocean cooling that is likely due to the Little Ice Age. In their paper published in the journal Science, Jake Gebbie and Peter Huybers describe their study of Pacific Ocean temperatures over the past 150 years and what they found.

The model showed that the Pacific Ocean cooled over the course of the 20th century at depths of 1.8 to 2.6 kilometers. The amount is still not precise, but the researchers suggest it is most likely between 0.02 and 0.08° C. That cooling, the researchers suggest, is likely due to the Little Ice Age, which ran from approximately 1300 until approximately 1870. Prior to that, there was a time known as the Medieval Warm Period, which had caused the deep waters of the Pacific to warm just prior to the cooling it is now experiencing.

Prior research has suggested that it takes a very long time for water in the Pacific Ocean to circulate down to its lowest depths. This is because it is replenished only from the south, which means it takes a very long time for water on the surface to make its way to the bottom – perhaps as long as several hundred years. That is what Gebbie and Huber found back in 2012. That got them to thinking that water temperature at the bottom of the Pacific could offer a hint of what surface temperatures were like hundreds of years ago.

To find out if that truly was the case, the researchers obtained data from an international consortium called the Argo Program – a group of people who together have been taking ocean measurements down to depths of approximately two kilometers. As a comparative reference, the researchers also obtained data gathered by the crew of the HMS Challenger – they had taken Pacific Ocean temperatures down to a depth of two kilometers during the years 1872 to 1876. The researchers used the data from both projects to build a computer model meant to mimic the circulation of water in the Pacific Ocean over the past century and a half.

Astronomers Detect an Intense Luminous Gamma-Ray Flare

An international group of astronomers has detected an intense and extremely luminous gamma-ray flare from one of high-redshift blazars known as DA 193. The new detection, reported in a paper published December 18 on arXiv.org, is an uncommon finding as such bright flares are rarely observed from high-redshift sources.

Blazars, classified as members of a larger group of active galaxies that host active galactic nuclei (AGN), are the most numerous extragalactic gamma-ray sources. Their characteristic features are relativistic jets pointed almost exactly toward the Earth. In general, blazars are perceived by astronomers as high-energy engines serving as natural laboratories to study particle acceleration, relativistic plasma processes, magnetic field dynamics and black hole physics.

Studies show that high-redshift blazars (with redshifts above 2.0) hosting massive black holes and the most powerful relativistic jets are the most luminous ones. Finding and observing new blazars at high redshifts could be crucial for providing insights into many phenomena of the universe, including the evolution and space density of massive black holes.

A team of researchers led by Vaidehi S. Paliya of DESY research center in Zeuthen, Germany, investigated one such high-redshift blazer. They used the Large Area Telescope (LAT) on board NASA’s Fermi Gamma-ray Space Telescope and other instruments to characterize physical properties DA 193 – a blazar observed close to the galactic anti-center at a redshift of approximately 2.36. These observations resulted in the detection of significant gamma-ray emission from this object.

“In this work, we present the results of our study on another high-redshift blazar DA 193 (also known as 0552+398; z = 2.363, Wills & Wills 1976; McIntosh et al. 1999) which we have found as a new gamma-ray emitting object through our detailed Fermi-LAT analysis,” the researchers wrote in the paper.

DA 193 underwent a significant GeV flare in the first week of 2018. According to the study, it was an extremely luminous gamma-ray flare with a luminosity of about 130 quindecillion erg/s.

The researchers note that such a GeV flare from a high-redshift blazar is a rare phenomenon. This is due to the fact that these blazars are generally faint in the gamma-ray band.

Notably, DA 193 has an extremely hard gamma-ray spectrum. “What makes this event a rare one is the observation of an extremely hard γ-ray spectrum (photon index = 1.7 ± 0.2), which is somewhat unexpected since high-redshift blazars typically exhibit a steep falling spectrum at GeV energies,” the paper reads.

Trying to determine what caused such an intense and luminous flare from DA 193, the astronomers suggest that a change in the behavior of the underlying electron population could be responsible for the observed event. The team intends to use LAT for further continuous monitoring of the gamma-ray sky in order to find more powerful blazars showcasing luminous flares like DA 193. Studying such events could lead to a better understanding of radiative processes powering relativistic jets in blazars.

NASA’s New Horizons Just Made the Most Distant Flyby in Space History

NASA’s unmanned New Horizons spacecraft is closing in on its historic New Year’s flyby target, the most distant world ever studied, a frozen relic of the solar system some four billion miles (6.4 billion kilometers) away. The cosmic object, known as Ultima Thule, is about the size of the US capital, Washington, and orbits in the dark and frigid Kuiper Belt about a billion miles beyond the dwarf planet, Pluto.

The spacecraft’s closest approach to this primitive space rock comes January 1 at 12:33 am ET (0533 GMT). Until then, what it looks like, and what it is made of, remain a mystery.

“This is a time capsule that is going to take us back four and a half billion years to the birth of the solar system,” said Alan Stern, the principal investigator on the project at the Southwest Research Institute, during a press briefing Friday. A camera on board the New Horizons spacecraft is currently zooming in on Ultima Thule, so scientists can get a better sense of its shape and configuration—whether it is one object or several.

“We’ve never been to a type of object like this before,” said Kelsi Singer, New Horizons co-investigator at the Southwest Research Institute. About a day prior, “we will start to see what the actual shape of the object is,” she said. The spacecraft entered “encounter mode” on December 26, and is “very healthy,” added Stern.

Communicating with a spacecraft that is so far away takes six hours and eight minutes each way – or about 12 hours and 15 minutes round trip.

New Horizons’ eagerly awaited “phone home” command, indicating if it survived the close pass – at a distance of just 2,200 miles (3,500 kilometers) is expected January 1 at 10:29 am (1529 GMT). Until then, the New Horizons spacecraft continues speeding through space at 32,000 miles (51,500 kilometers) per hour, traveling almost a million miles per day.
And NASA scientists are eagerly awaiting the first images.

“Because this is a flyby mission, we only have one chance to get it right,” said Alice Bowman, missions operations manager for New Horizons. The spacecraft, which launched in 2006, captured stunning images of Pluto when it flew by the dwarf planet in 2015.

No Tsunami Threat To Hawaii From Alaska Earthquake

The Pacific Tsunami Warning Center said a magnitude 6.1 earthquake that struck Alaska today poses no local threat of a tsunami.

 

A earthquake magnitude 6.1 (ml/mb) has struck on Sunday, 116 km SE of Cold Bay, Alaska (72 miles). Exact location, longitude -161.4719° West, latitude 54.4279° North, depth = 26.92 km.

The 6.1-magnitude earthquake has occurred at 15:35:37 / 3:35 pm (local time epicenter). A tsunami warning has been issued near Cold Bay in Alaska (Does not indicate if a tsunami actually did or will exist).

Bali Volcano Shoots New Burst Of Ash; Flights Unaffected

A volcano on Indonesia’s tourist island of Bali shot a new burst of hot ash into the air early Sunday in the latest of the country’s several eruptions within a week.

Mount Agung erupted for about three minutes, spewing white clouds of smoke and ash more than 700 meters (2,300 feet) into the air, the Volcanology and Geological Mitigation Agency said in a statement.

The eruption of the 3,031-meter (9,940-foot) volcano didn’t prompt evacuations, and its alert status remains at the second-highest level. The agency warned tourists to stay away from the danger zone in a 4-kilometer (2.5-mile) radius around the crater.

Agency spokesman Sutopo Purwo Nugroho said that white dust from the eruption blanketed several villages close to the mountain slope in Karangasem district.

Ngurah Rai International Airport spokesman Arie Ahsanurrohim said that flights were operating normally. Authorities said the air around Denpasar, the Bali provincial capital, is clear from ash.

More than 140,000 people had fled the area around the mountain in late September after its alert status was raised to the highest level, indicating an eruption may be imminent. The alert status was lowered two weeks later, allowing for the return of those displaced from government shelters.

An eruption in 1963 killed about 1,100 people. Agung lies about 70 kilometers (45 miles) northeast of Bali’s tourist hotspot of Kuta.

It is among more than 120 active volcanoes in Indonesia, which is prone to volcanic eruptions and earthquakes because of its location on the so-called “Ring of Fire” — a series of fault lines stretching from the Western Hemisphere through Japan and Southeast Asia.

Last week, Anak Krakatau in Indonesia’s Sunda Straits erupted and collapsed into the sea, causing a tsunami that killed 431 people on Java and Sumatra. More than 46,600 were displaced.