Questões de Concurso

(1º§)Archaeologists have long assumed that the ancient society that erected the colossal Moai figures on Chile's Rapa Nui, better known as Easter Island, collapsed many centuries ago. Now, a new study indicates that the islanders' civilization was still going strong when Europeans arrived in 1722.

(2º§)The island was settled in the 13th century by Polynesians, and is known __ the famed Easter Island "heads" (many of the bodies have been buried by erosion over the centuries).

(3º§)The research, which appears in the Journal of Archaeological Science, contests the accepted timeline that the Easter Island society was already in decline by the year 1600 and its massive stone statues left to fall into disrepair.

(4º§)Conducting radiocarbon dating on 11 sites __ Easter Island, the authors determined the timeline of each monument's construction. Their findings indicate that Easter Islanders were still actively building new Moai figures, and maintaining existing ones, up until at least 1750.s of fresh water-a precious resource. As well as moments to their ancestors, it turns out they may have also served a more utilitarian purpose.

(5º§)Further supporting these results are historical documents __ the island's first European visitors. Written accounts from the Dutch explorers who arrived in 1722 found that the monuments were in active ritual use, with no signs of decline, and the same goes for the Spaniards who landed in 1770. It was only in 1774 that James Cook found the giant statues in ruins and the figures knocked over.

(6º§)"The way we interpret our results and this sequence of historical accounts is that the notion of a pre-European collapse of monument construction is no longer supported," lead author Robert DiNapoli told Archaeology & Arts.

(7º§)"Once Europeans arrive on the island, there are many documented tragic events due to disease, murder, slave raiding and other conflicts," added co-author Carl Lipo. "The degree to which [the Rapa Nui people's] cultural heritage was passed on-and is still present today through language, arts, and cultural practices-is quite notable and impressive. I think this degree of resilience has been overlooked due to the collapse narrative and deserves recognition."

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(1º§)Archaeologists have long assumed that the ancient society that erected the colossal Moai figures on Chile's Rapa Nui, better known as Easter Island, collapsed many centuries ago. Now, a new study indicates that the islanders' civilization was still going strong when Europeans arrived in 1722.

(2º§)The island was settled in the 13th century by Polynesians, and is known __ the famed Easter Island "heads" (many of the bodies have been buried by erosion over the centuries).

(3º§)The research, which appears in the Journal of Archaeological Science, contests the accepted timeline that the Easter Island society was already in decline by the year 1600 and its massive stone statues left to fall into disrepair.

(4º§)Conducting radiocarbon dating on 11 sites __ Easter Island, the authors determined the timeline of each monument's construction. Their findings indicate that Easter Islanders were still actively building new Moai figures, and maintaining existing ones, up until at least 1750.s of fresh water-a precious resource. As well as moments to their ancestors, it turns out they may have also served a more utilitarian purpose.

(5º§)Further supporting these results are historical documents __ the island's first European visitors. Written accounts from the Dutch explorers who arrived in 1722 found that the monuments were in active ritual use, with no signs of decline, and the same goes for the Spaniards who landed in 1770. It was only in 1774 that James Cook found the giant statues in ruins and the figures knocked over.

(6º§)"The way we interpret our results and this sequence of historical accounts is that the notion of a pre-European collapse of monument construction is no longer supported," lead author Robert DiNapoli told Archaeology & Arts.

(7º§)"Once Europeans arrive on the island, there are many documented tragic events due to disease, murder, slave raiding and other conflicts," added co-author Carl Lipo. "The degree to which [the Rapa Nui people's] cultural heritage was passed on-and is still present today through language, arts, and cultural practices-is quite notable and impressive. I think this degree of resilience has been overlooked due to the collapse narrative and deserves recognition."

777281144

(1º§)Archaeologists have long assumed that the ancient society that erected the colossal Moai figures on Chile's Rapa Nui, better known as Easter Island, collapsed many centuries ago. Now, a new study indicates that the islanders' civilization was still going strong when Europeans arrived in 1722.

(2º§)The island was settled in the 13th century by Polynesians, and is known __ the famed Easter Island "heads" (many of the bodies have been buried by erosion over the centuries).

(3º§)The research, which appears in the Journal of Archaeological Science, contests the accepted timeline that the Easter Island society was already in decline by the year 1600 and its massive stone statues left to fall into disrepair.

(4º§)Conducting radiocarbon dating on 11 sites __ Easter Island, the authors determined the timeline of each monument's construction. Their findings indicate that Easter Islanders were still actively building new Moai figures, and maintaining existing ones, up until at least 1750.s of fresh water-a precious resource. As well as moments to their ancestors, it turns out they may have also served a more utilitarian purpose.

(5º§)Further supporting these results are historical documents __ the island's first European visitors. Written accounts from the Dutch explorers who arrived in 1722 found that the monuments were in active ritual use, with no signs of decline, and the same goes for the Spaniards who landed in 1770. It was only in 1774 that James Cook found the giant statues in ruins and the figures knocked over.

(6º§)"The way we interpret our results and this sequence of historical accounts is that the notion of a pre-European collapse of monument construction is no longer supported," lead author Robert DiNapoli told Archaeology & Arts.

(7º§)"Once Europeans arrive on the island, there are many documented tragic events due to disease, murder, slave raiding and other conflicts," added co-author Carl Lipo. "The degree to which [the Rapa Nui people's] cultural heritage was passed on-and is still present today through language, arts, and cultural practices-is quite notable and impressive. I think this degree of resilience has been overlooked due to the collapse narrative and deserves recognition."

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(1º§)Volcanoes can impact climate change. During major explosive eruptions huge amounts__volcanic gas, aerosol droplets, and ash are injected into the stratosphere. Injected ash falls rapidly from the stratosphere -- most of it is removed within several days to weeks -- and has little impact on climate change. But volcanic gases like sulfur dioxide can cause global cooling, while volcanic carbon dioxide, a greenhouse gas, has the potential to promote global warming.

(2º§)The most significant climate impacts from volcanic injections into the stratosphere come from the conversion of sulfur dioxide to sulfuric acid, which condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols increase the reflection of radiation from the Sun back into space, cooling the Earth's lower atmosphere or troposphere.

(3º§)Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to three years. The climactic eruption of Mount Pinatubo on June 15, 1991, was one of the largest eruptions of the twentieth century and injected a 20-million ton (metric scale) sulfur dioxide cloud into the stratosphere at an altitude of more than 20 miles. The Pinatubo cloud was the largest sulfur dioxide cloud ever observed in the stratosphere since the beginning of such observations by satellites in 1978. It caused what is believed to be the largest aerosol disturbance of the stratosphere in the twentieth century, though probably smaller than the disturbances from eruptions of Krakatau in 1883 and Tambora in 1815. Consequently, it was a standout in its climate impact and cooled the Earth's surface for three years following the eruption, by as much as 1.3 degrees F at the height of the impact.

(4º§)The large 1783-1784 Laki fissure eruption in Iceland released a staggering amount more sulfur dioxide than Pinatubo (approximately 120-million ton vs. 20). Although the two eruptions were significantly different__length and style, the added atmospheric SO2 caused regional cooling of Europe and North America by similar amounts for similar periods of time.

(5º§)Carbon dioxide (CO2) is a greenhouse gas and is the primary gas blamed for climate change. While sulfur dioxide released in contemporary volcanic eruptions has occasionally caused detectable global cooling of the lower atmosphere, the carbon dioxide released in contemporary volcanic eruptions has never caused detectable global warming of the atmosphere. In 2010, human activities were responsible for a projected 35 billion metric tons (gigatons) of CO2 emissions. All studies to date of global volcanic carbon dioxide emissions indicate that present-day subaerial and submarine volcanoes release less than a percent of the carbon dioxide released currently by human activities. While it has been proposed that intense volcanic release of carbon dioxide in the deep geologic past did cause global warming, and possibly some mass extinctions, this is a topic of scientific debate at present.

(6º§)Published scientific estimates of the global CO2 emission rate for all degassing subaerial (on land) and submarine volcanoes lie in a range from 0.13 gigaton to 0.44 gigaton per year. The 35-gigaton projected anthropogenic CO2 emission for 2010 is about 80 to 270 times larger than the respective maximum and minimum annual global volcanic CO2 emission estimates.

(7º§)There is no question that very large volcanic eruptions can inject significant amounts of carbon dioxide into the atmosphere. The 1980 eruption of Mount St. Helens vented approximately 10 million tons of CO2 into the atmosphere in only 9 hours. However, it currently takes humanity only 2.5 hours to put out the same amount. While large explosive eruptions like this are rare and only occur globally every 10 years or so, humanity's emissions are ceaseless and increasing every year.

(8º§)There continues to be efforts to reduce uncertainties and improve estimates of present-day global volcanic CO2 emissions, but there is little doubt among volcanic gas scientists that the anthropogenic CO2 emissions dwarf global volcanic CO2 emissions.

(9º§)For additional information about this subject, please read the American Geophysical Union's Eos article "Volcanic Versus Anthropogenic Carbon Dioxide" written__USGS scientist Terrence M. Gerlach.

https://www.usgs.gov/programs/VHP/