是什麼造成了壯觀的夏威夷-天皇海山鍊(Hawaiian-Emperor seamount chain)變得如此彎折？

原始網址：www.sciencedaily.com/releases/2016/05/160511142351.htm

How the spectacular Hawaiian-Emperor seamount chain became so bendy

是什麼造成了壯觀的夏威夷-天皇海山鍊(Hawaiian-Emperor seamount chain)變得如此彎折？

The physical mechanism causing the unique, sharp bend in the Hawaiian-Emperor seamount chain has been uncovered in a collaboration between the University of Sydney and the California Institute of Technology (Caltech).

在雪梨大學和加州理工學院的合作之下，終於找出了可以用來解釋夏威夷-天皇海山鍊中獨一無二的急轉彎是如何形成的物理機制。

Led by a PhD candidate at the University of Sydney's School of Geosciences, researchers used the Southern Hemisphere's most highly integrated supercomputer to reveal flow patterns deep in the Earth's mantle -- just above the core -- over the past 100 million years. The flow patterns explain how the enigmatic bend in the Hawaiian-Emperor seamount chain arose.

在雪梨大學地質科學院的博士候選人領導之下，研究人員利用南半球效能最強的超級電腦展現出緊鄰地核正上方的深層地函過去1億年來的流動模式。這可以用來解釋夏威夷-天皇海山鍊中謎樣的轉折究竟是如何形成。

True to the old adage -- as above, so below -- the Sydney-US collaboration found the shape of volcanic seamount chains (chains of mostly extinct volcanoes), including Hawaii, is intimately linked to motion near the Earth's core.

如同一句古老格言所說：「如其在上，如其在下(As above, so below)。」雪梨跟美國大學的合作成果發現了包括夏威夷在內的海山鍊(排成鍊狀的火山，其中大都為死火山)，其形態跟地核附近的地函運動息息相關。

The findings of PhD candidate Rakib Hassan and fellow researchers including Professor Dietmar Müller from the University's EarthByte Group, are being published in Nature.

此篇刊登於《自然》的研究由博士候選人Rakib Hassan 進行，共同研究人員包括了雪梨大學地球位元團隊的成員之一， Dietmar Müller教授。

Mr Hassan explained: "Until now, scientists believed the spectacular 60° bend in the Hawaiian seamount chain -- not found in any other seamount chains -- was related to a change in plate motion combined with a change in flow direction in the shallow mantle, the layer of thick rock between the Earth's crust and its core.

Hassan解釋：「目前為止科學家仍然認為出現在夏威夷海山鍊中十分引人注目的60度彎曲，這項未在其他海山鍊中出現的特徵，跟板塊運動方向以及淺層地函流向的改變有關。地函是位在地球地核跟地殼中間，厚度相當厚的岩石。」

"These findings suggest the shape of volcanic seamount chains record motion in the deepest mantle, near the Earth's core. The more coherent and rapid the motion deep in the mantle, the more acute its effects are on the shape of seamount chains above," he said.

「這項發現也告訴我們海底火山鍊的型態紀錄了地核附近的深層地函是如何運動。地函深部的運動越一致且迅速，對上方海山鍊型態造成的影響就會越劇烈。」他說。

Although solid, the mantle is in a state of continuous flow, observable only over geological timescales. Vertical columns of hot and buoyant rock rising through the mantle from near the core are known as mantle plumes. Volcanic seamount chains such as Hawaii were created from magma produced near the surface by mantle plumes. Moving tectonic plates sit above the mantle and carry newly formed seamounts away from the plume underneath -- the oldest seamounts in a chain are therefore furthest away from the plume.

地函雖為固體，但它其實處於持續緩緩流動的狀態，不過這樣的運動只能從地質時間尺度來看才能觀察到。稱作地函柱(mantle plume)的高熱且上湧的柱狀岩石會從將近地核處往上升並穿過地函，它在接近地表處產生的岩漿會形成像夏威夷這類的海底火山鍊。在地函上方移動的板塊會將新形成的海山帶離下方的地函柱，造成海山鍊中最老的海山會離地函柱最遠。

"We had an intuition that, since the north Pacific experienced a prolonged phase where large, cold tectonic plates uninterruptedly sank into the mantle, the flow in the deepest mantle there would be very different compared to other regions of the Earth," Mr Hassan said.

「既然北太平洋很長一段時間都處於低溫的大型板塊不斷往地函下沉的環境，直覺告訴我們在這裡地函最深處的運動必然會跟地球上其他地區大不相同。」 Hassan說。

One of the most contentious debates in geoscience has centred on whether piles of rock in the deep mantle -- to which plumes are anchored -- have remained stationary, unaffected by mantle flow over hundreds of millions of years.

地質科學中最眾說紛紜的爭論之一便聚焦於地函深處的岩石，也就是地函柱的根基所在，是否在數億年的時光中能固定在同一個地方，不受地函流動影響。

The new research shows the shapes of these piles have changed through time and their shapes can be strongly dependent on rapid, coherent flow in the deep mantle.

這項新研究顯示這些岩石的形狀會隨著時間變化，且跟深部地函一致且迅速的流動密切相關。

Between 50-100 million years ago, the edge of the pile under the north Pacific was pushed rapidly southward, along with the base of Hawaii's volcanic plume, causing it to tilt. The plume became vertical again once the motion of its base stopped; this dramatic start-stop motion resulted in the seamount chain's sharp bend.

在5000萬年到1億年前，在北太平洋之下這些岩石的邊界迅速地往南推進，夏威夷火山地函柱的根基也連帶著移動，使得整根地函柱傾斜。然而，一旦這個運動停止下來，地函柱便會再次回復直立的狀態。這種劇烈地停止及運動的交互發生，造成海山鍊發生急遽的轉彎。

Using Australia's National Computational Infrastructure's supercomputer Raijin, the team created high-resolution three-dimensional simulations of mantle evolution over the past 200 million years to understand the coupling between convection in the deep Earth and volcanism.

研究團隊利用澳洲國家計算基礎建設中心的超級電腦「雷神(Raijin)」創建了高解析度的三維模型，可以顯現過去2億年來地函的演化過程，並從中了解地球深部的對流跟火山活動之間的關聯。

Mr Hassan said the simulations were guided by surface observations -- similar to meteorologists applying past measurements to predict the weather.

Hassan先生說這項模擬是以地表的觀測結果為基礎來進行，這跟大氣學家利用過往累積的觀測結果來預報天氣之間有異曲同工之處。

"These simulations required millions of central processing unit (CPU) hours on the supercomputer over the course of the project," he said.

「在整個計畫執行的過程中，光是進行模擬就得花上超級電腦的中央處理器數百萬個小時。」他說。

Professor Müller concluded: "Our results help resolve a major enigma of why volcanic seamount chains on the same tectonic plate can have very different shapes.

Müller教授總結說：「我們的結果可以幫助科學家解答這個謎題：為什麼在同一座板塊中，不同海底火山鍊之間的型態可以如此截然不同。」

"It is now clear that we first need to understand the dynamics of the deepest 'Underworld', right above the core, to unravel the history of volcanism at Earth's surface," said Professor Müller.

「我們現在相當明瞭首先要了解『地底世界』的最深處，也就是緊鄰地核處發生了何種動力過程，才能闡明地表火山活動為何會擁有這樣的歷史。」 Müller教授說。

Watch the animation here https://youtu.be/Xy5kHjAHXec

連結此網址來觀看動畫https://youtu.be/Xy5kHjAHXec

引用自：University of Sydney. "How the spectacular Hawaiian-Emperor seamount chain became so bendy." ScienceDaily. ScienceDaily, 11 May 2016. 

地球早期空氣的重量不到現在大氣的一半

原始網址：www.sciencedaily.com/releases/2016/05/160509115114.htm

Early Earth's air weighed less than half of today's atmosphere

地球早期空氣的重量不到現在大氣的一半

The idea that the young Earth had a thicker atmosphere turns out to be wrong. New research from the University of Washington uses bubbles trapped in 2.7 billion-year-old rocks to show that air at that time exerted at most half the pressure of today's atmosphere.

地球幼年時擁有厚重大氣層的想法現在看來似乎是錯的。華盛頓大學進行的新研究利用了27億年前困在岩石中的氣泡，顯示當時空氣造成的壓力頂多只有現今大氣的一半而已。

The results, published online May 9 in Nature Geoscience, reverse the commonly accepted idea that the early Earth had a thicker atmosphere to compensate for weaker sunlight. The finding also has implications for which gases were in that atmosphere, and how biology and climate worked on the early planet.

以往被廣為接受的想法中認為早期地球擁有厚重的大氣層並遮蔽了陽光，但刊登在5月9日《自然—地質科學》(Nature Geoscience)線上版的研究結果卻顛覆了這個說法。這項發現對於了解地球早期的空氣成分、氣候運作方式和生物的行為，也都具有相當的啟發。

"For the longest time, people have been thinking the atmospheric pressure might have been higher back then, because the sun was fainter," said lead author Sanjoy Som, who did the work as part of his UW doctorate in Earth and space sciences. "Our result is the opposite of what we were expecting."

「一直以來人們都因為當時的陽光較現今微弱，而認為那時的大氣壓力會比較高。」第一作者Sanjoy Som說。這是他於華盛頓大學攻讀地球與太空科學博士學位時進行的研究中的一部分。「然而我們的成果卻跟我們預設的恰好相反。」

The idea of using bubbles trapped in cooling lava as a "paleobarometer" to determine the weight of air in our planet's youth occurred decades ago to co-author Roger Buick, a UW professor of Earth and space sciences. Others had used the technique to measure the elevation of lavas a few million years old. To flip the idea and measure air pressure farther back in time, researchers needed a site where truly ancient lava had undisputedly formed at sea level.

華盛頓大學地球與太空科學教授Roger Buick，同時也是本文的共同作者，在幾十年前就已經想到說可以把岩漿冷卻後困在其中的氣泡作為「古氣壓計」，來測量地球年輕時大氣的重量。其他的研究通常用這項技術測定數百萬年前岩漿噴發時位於的海拔高度。但本篇研究的人員則反向利用這個概念來得知過去的大氣壓力，為了執行這個想法，他們需要一處年代十分久遠的熔岩，其生成位置必須要位於海平面的高度。

Their field site in Western Australia was discovered by co-author Tim Blake of the University of Western Australia. There, the Beasley River has exposed 2.7 billion-year-old basalt lava. The lowest lava flow has "lava toes" that burrow into glassy shards, proving that molten lava plunged into seawater. The team drilled into the overlying lava flows to examine the size of the bubbles.

他們的野外工作地點是由共同作者，西澳大學的Tim Blake 發現。稱作Beasley River的這個地方有27億年前的玄武岩熔岩出露。他們發現熔岩流在地勢最低處的「熔岩趾(lava toe)」具有玻璃質孔洞，證實了這片熔岩流曾經流進海水當中。研究團隊接著在上方的熔岩流上鑽孔，以檢視氣泡的大小。

A stream of molten rock quickly cools from top and bottom, and bubbles trapped at the bottom are smaller than those at the top. The size difference records the air pressure pushing down on the lava as it cooled, 2.7 billion years ago.

熔岩流動時會從上而下快速地冷卻，造成困於底部的氣泡會比頂端的要小。它們的尺寸差距即成為了27億年前，熔岩冷卻當下大氣對它施加壓力大小的紀錄。

Rough measurements in the field suggested a surprisingly lightweight atmosphere. More rigorous x-ray scans from several lava flows confirmed the result: The bubbles indicate that the atmospheric pressure at that time was less than half of today's.

在野外粗略的估計就顯示出當時大氣重量輕的令人驚訝。在以更加精確的X光掃描了數個熔岩流樣品後確立了以下結論：氣泡指出當時的大氣壓力比現在的一半還要低。

Earth 2.7 billion years ago was home only to single-celled microbes, sunlight was about one-fifth weaker, and the atmosphere contained no oxygen. But this finding points to conditions being even more otherworldly than previously thought. A lighter atmosphere could affect wind strength and other climate patterns, and would even alter the boiling point of liquids.

27億年前的地球僅有一些單細胞生物生存於此，而陽光比現在弱了將近8成，大氣也完全沒有氧氣。但這個發現指出當時的地球可能比之前認為的更像外星世界。較稀薄的大氣會影響風的強度以及其他氣候模式，甚至還會改變液體的沸點。

"We're still coming to grips with the magnitude of this," Buick said. "It's going to take us a while to digest all the possible consequences." Other geological evidence clearly shows liquid water on Earth at that time, so the early atmosphere must have contained more heat-trapping greenhouse gases, like methane and carbon dioxide, and less nitrogen.

「我們仍然在釐清這會帶來多大的影響。」Buick說。「要整理出所有可能發生的效應得花上我們一段時間。」其他的地質證據顯示當時地表已經擁有液態水，因此早期大氣勢必要含有更多可以關住熱量的溫室氣體，像是甲烷、二氧化碳以及少量的氮氣。

The new study is an advance on the UW team's previous work on "fossilized raindrops" that first cast doubt on the idea of a far thicker ancient atmosphere. The result also reinforces Buick's 2015 finding that microbes were pulling nitrogen out of Earth's atmosphere some 3 billion years ago.

華盛頓大學團隊繼先前以「雨滴化石」的研究而首度對遠古大氣相當濃厚的說法拋出質疑後，這篇研究更進一步地鞏固了他們的論述。結論也支持了Buick於2015年發現將近30億年前的微生物，會從地球大氣中吸收氮氣的研究。

"The levels of nitrogen gas have varied through Earth's history, at least in Earth's early history, in ways that people just haven't even thought of before," said co-author David Catling, a UW professor of Earth and space sciences. "People will need to rewrite the textbooks."

「直到不久前才有人去仔細思考在整個地球歷史，或者至少是在地球歷史的早期，氮氣在大氣中的濃度是如何變化的。」共同作者，華盛頓大學的地球與太空科學家David Catling說。「人們需要為此而重新編撰教科書。」

The researchers will next look for other suitable rocks to confirm the findings and learn how atmospheric pressure might have varied through time.

研究人員接下來的目標是放在尋找其他符合條件的岩石，以驗證他們的發現並且試著去了解大氣壓力隨著時間可能是如何變化的。

While clues to the early Earth are scarce, it is still easier to study than planets outside our solar system, so this will help understand possible conditions and life on other planets where atmospheres might be thin and oxygen-free, like that of the early Earth.

雖然關於早期地球樣貌的是如此稀少，但是跟研究太陽系之外的行星一比還是簡單許多，因此這或許有助於我們了解跟早期地球相似，大氣層稀薄且不含氧氣的其他行星上的環境條件以及生命形式可能的樣貌。

Som is CEO of Seattle-based Blue Marble Space, a nonprofit that focuses on interdisciplinary space science research, international awareness, science education and public outreach. He currently does astrobiology research at NASA's Ames Research Center in California.

Som是Blue Marble Space組織的執行長，此非營利組織位於西雅圖，主要業務著重於跨領域太空科學研究、國際關懷事務、科學教育及推廣ㄧ。他目前於加州NASA艾姆斯研究中心從事有關天體生物學的研究。

引用自：University of Washington. "Early Earth's air weighed less than half of today's atmosphere." ScienceDaily. ScienceDaily, 9 May 2016. 

地球化學偵探利用實驗室模擬來回推過去

原文網址：www.sciencedaily.com/releases/2016/04/160428151836.htm

Geochemical detectives use lab mimicry to look back in time

地球化學偵探利用實驗室模擬來回推過去

New work from a research team led by Carnegie's Anat Shahar contains some unexpected findings about iron chemistry under high-pressure conditions, such as those likely found in the Earth's core, where iron predominates and creates our planet's life-shielding magnetic field. Their results, published in Science, could shed light on Earth's early days when the core was formed through a process called differentiation--when the denser materials, like iron, sunk inward toward the center, creating the layered composition the planet has today.

由卡內基實驗室的Anat Shahar領導的研究團隊最新發表的工作成果中，包含了某些意料之外的發現：有關於鐵的化學性質在高壓環境之下的行為。地核可能即屬這種環境，此處的成分以鐵為主，並由此產生了保護地球生命的磁場。他們刊登在期刊《科學》(Science)的成果，或許可以闡明當地球年幼時，地核經由「分異作用」(differentiation)而形成時的細節。當這種作用發生時，像鐵這類密度較高的物質會往下沉至地球中心，使得今日的地球成分呈現層狀分布。

Earth formed from accreted matter surrounding the young Sun. Over time, the iron in this early planetary material moved inward, separating from the surrounding silicate. This process created the planet's iron core and silicate upper mantle. But much about this how this differentiation process occurred is still poorly understood, due to the technological impossibility of taking samples from the Earth's core to see which compounds exist there.

地球是由環繞在幼年太陽周遭的物質聚積而成。隨著時間流逝，這些初生行星物質中的鐵會逐漸往內部移動，而跟周圍的矽酸鹽分離開來。這種作用使得地球擁有鐵質核心以及位於上方的矽酸鹽質地函。但有關於這種分異作用的更多細節究竟是如何進行，卻還是所知甚少。這是因為技術上的限制使我們不可能從地核取得樣品，觀察存在於此的到底是什麼物質。

Seismic data show that in addition to iron, there are "lighter" elements present in the core, but which elements and in what concentrations they exist has been a matter of great debate. This is because as the iron moved inward toward the core, it interacted with various lighter elements to form different alloyed compounds, which were then carried along with the iron into the planet's depths.

地震波資料顯示除了鐵之外，地核內部還有其他較「輕」的元素，但是這些元素的真實身分以及濃度多寡仍然眾說紛紜。這是因為當鐵往下沉至地核的旅途中，它會跟周遭各式各樣的較輕元素交互作用，而產生許多種不同的合金，接著它們會夥同鐵一起進入地球深處。

Which elements iron bonded with during this time would have been determined by the surrounding conditions, including pressure and temperature. As a result, working backward and determining which iron alloy compounds were created during differentiation could tell scientists about the conditions on early Earth and about the planet's geochemical evolution.

在這段時期鐵會跟什麼樣的元素結合跟它們所處的環境條件有關，像是溫度和壓力。因此，反過來研究並找出在分異作用進行時形成的合金種類，可以告訴科學家早期地球的環境條件，以及地球的化學性質如何演變。

The team--including Carnegie's Jinfu Shu and Yuming Xiao--decided to investigate this subject by researching how pressures mimicking the Earth's core would affect the composition of iron isotopes in various alloys of iron and light elements. Isotopes are versions of an element where the number of neutrons differs from the number of protons. (Each element contains a unique number of protons.)

包括Jinfu Shu和Yuming Xiao這兩位卡內基科學家的研究團隊決定研究這道難題。他們用的方法是模擬鐵和輕元素的不同合金中，鐵的同位素成分會如何受地核內部壓力高低影響。同位素是隸屬同一種元素但中子數不同的版本，這點與質子數並不相同(每一種元素都有各自獨一無二的質子數)。

Because of this accounting difference, isotopes' masses are not the same, which can sometimes cause small variations in how different isotopes of the same element are partitioned in, or are "picked up" by, either silicate or iron metal. Some isotopes are preferred by certain reactions, which results in an imbalance in the proportion of each isotope incorporated into the end products of these reactions--a process that can leave behind trace isotopic signatures in rocks. This phenomenon is called isotope fractionation and is crucial to the team's research.

由於在中子數目上的差異，同位素的質量也各不相同，這種微小的差異有時會導致矽酸鹽或金屬鐵在分配(partition)，也就是「揀選」同一元素的同位素時會有些許的不同。特定反應會偏好某些種類的同位素，這會導致每一種同位素的比例在各個反應終產物中的分配並不均衡。這種過程可以在岩石當中留下可供追循的同位素訊號。對此團隊的研究來說，這種稱作同位素分餾(isotope fractionation)的現象相當重要。

Before now, pressure was not considered a critical variable affecting isotope fractionation. But Shahar and her team's research demonstrated that for iron, extreme pressure conditions do affect isotope fractionation.

在此之前，科學家並不認為壓力是影響同位素分餾的重要因素。但Shahar 和她的團隊在研究中顯示，對鐵而言，極端的壓力環境確實會影響同位素分餾。

More importantly, the team discovered that due to this high-pressure fractionation, reactions between iron and two of the light elements often considered likely to be present in the core--hydrogen and carbon--would have left behind an isotopic signature in the mantle silicate as they reacted with iron and sunk to the core. But this isotopic signature has not been found in samples of mantle rock, so scientists can exclude them from the list of potential light elements in the core.

更重要的是，研究團隊發現由於高壓分餾作用的進行，兩種常被視為可能出現在地核中的輕元素—氫和碳，在跟鐵產生反應並往下沉至地核的過程中，會在地函矽酸鹽內留下某種同位素訊號。然而目前為止還尚未在地函岩石的樣品當中找到這種同位素訊號，因此科學家可以將氫和碳從可能出現在地函的輕元素名單上剔除。

Oxygen, on the other hand, would not have left an isotopic signature behind in the mantle, so it is still on the table. Likewise, other potential core light elements still need to be investigated, including silicon and sulfur.

另一方面，氧並不會在地函留下同位素訊號，因此它仍然列於名單上。類似地，其他可能出現在地函，像是矽和硫之類的輕元素還有待調查。

"What does this mean? It means we are gaining a better understanding of our planet's chemical and physical history," Shahar explained. "Although Earth is our home, there is still so much about its interior that we don't understand. But evidence that extreme pressures affect how isotopes partition, in ways that we can see traces of in rock samples, is a huge step forward in learning about our planet's geochemical evolution."

「這意味著什麼？這代表說我們對我們星球的化學和物理發展史有了更深一層的認識。」Shahar如此解釋。「雖然地球是我們的家園，但我們對它的內部仍有諸多不瞭解之處。然而，現在我們有了證據顯示極度的高壓會影響同位素分餾作用，而我們可以從岩石樣本中看到這種作用留下來的痕跡。對了解我們星球的地球化學是如何演變來說，這是相當重大的進展。」

引用自：Carnegie Institution for Science. "Geochemical detectives use lab mimicry to look back in time." ScienceDaily. ScienceDaily, 28 April 2016. 

地球最老礦物源自何方？

原文網址：www.sciencedaily.com/releases/2016/04/160428173233.htm

Origin of Earth's oldest crystals

地球最老礦物源自何方？

New research suggests that the very oldest pieces of rock on Earth -- zircon crystals -- are likely to have formed in the craters left by violent asteroid impacts that peppered our nascent planet, rather than via plate tectonics as was previously believed. Rocks that formed over the course of Earth's history allow geologists to infer things such as when water first appeared on the planet, how our climate has varied, and even where life came from. However, we can only go back in time so far, as the only material we have from the very early Earth comes in the form of tiny, naturally zircon crystals.

最新的研究提出地球上最老的岩石碎片—即鋯石的晶體，可能是小行星群猛烈轟炸初生地球後，在留下來的隕石坑內部形成，而非先前認為的是由板塊運動產生。在地球歷史漫漫軌跡中形成的諸多岩石可以讓地質學家從中推論出種種事物，像是地球上何時出現第一滴水，我們的氣候如何變化，甚至是生命的源頭。然而，至今我們僅能追溯自唯一從地球相當早期遺留下來的物質，也就是這些自然產生的微小鋯石結晶形成之時。

Naturally then, the origin of these crystals, which are approximately the width of a human hair and more than four billion years old (the Earth being just over four and a half billion years old), has become a matter of major debate. Fifteen years ago these crystals first made headlines when they revealed the presence of water on the surface of the Earth (thought to be a key ingredient for the origin of life) when they were forming.

自然而然地，這些僅約人髮寬，年代超過40億年的礦物起源為何，之後便成為一項眾說紛紜的議題。15年前，這些礦物因為顯示出在它們形成的時候地球表面已經有水(被認為是生物起源所需的關鍵要素之一)而首度聲名大噪。

Ten years ago, a team of researchers in the US1 argued that the ancient zircon crystals probably formed when tectonic plates moving around on the Earth's surface collided with each other in a similar fashion to the disruption taking place in the Andes Mountains today, where the ocean floor under the Pacific Ocean is plunging under South America.

10年前，一群來自US1的研究人員聲稱這些古老的鋯石結晶可能形成於板塊在地球表面移動而彼此碰撞時，就像今日太平洋底部的海床俯衝至南美洲之下，而在安地斯山脈內部發生的劇烈變動一般。

However, current evidence suggests that plate tectonics -- as we know it today -- was not occurring on the early Earth. So, the question remained: Where did the crystals come from?

然而，現有的證據顯示出我們今日熟悉的板塊構造運動在地球早期還尚未發生。因此問題仍然懸而未解：這些結晶究竟來自何方？

Recently, geologists suggested these grains may have formed in huge impact craters produced as chunks of rock from space, up to several kilometres in diameter, slammed into a young Earth. To test this idea, researchers from Trinity College Dublin decided to study a much younger impact crater to see if zircon crystals similar to the very old ones could possibly have formed in these violent settings.

最近，地質學家提出的一則新說法認為由半徑最高可達7公里，從太空來的岩石群重擊年幼地球時，所產生的巨大撞擊坑中形成了這些礦物顆粒。為了證實他們的想法，都柏林聖三一大學的研究人員決定研究年輕許多的撞擊坑，以觀察在這種嚴酷的環境當中，是否會產生跟那些相當古老的鋯石十分相似的鋯石結晶。

In the summer of 2014, with the support of the Irish Reseach Council (IRC) and Science Foundation Ireland (SFI), the team collected thousands of zircons from the Sudbury impact crater, Ontario, Canada -- the best preserved large impact crater on Earth and the planet's second oldest confirmed crater at almost two billion years old.

2014年夏季，在愛爾蘭研究學會和愛爾蘭科學基金會的協助之下，研究團隊從加拿大安大略省的索德柏立(Sudbury)撞擊坑中採集了數以千計的鋯石。這個撞擊坑是地球上被研究得最為透徹的大型撞擊坑，同時也是已確認年代的撞擊坑中第二古老者，年代將近20億年。

After analysing these crystals at the Swedish Museum of Natural History in Stockholm, they discovered that the crystal compositions were indistinguishable from the ancient set.

在斯德哥爾摩的瑞典自然史博物館中詳盡分析這些晶體後，他們發現這些晶體的成分幾乎無法跟那些古老的鋯石區分開來。

PhD Researcher in Trinity's School of Natural Sciences, Gavin Kenny, is first author of the article which explains these findings, and which has just been published in leading international journal, Geology.

此篇論文的第一作者，聖三一大學自然科學院的博士後研究員 Gavin Kenny解釋了他們剛刊登於國際頂尖期刊《地質》(Geology)上的新發現。

He said: "What we found was quite surprising. Many people thought the very ancient zircon crystals couldn't have formed in impact craters, but we now know they could have. There's a lot we still don't fully understand about these little guys but it looks like we may now be able to form a more coherent story of Earth's early years -- one which fits with the idea that our planet suffered far more frequent bombardment from asteroids early on than it has in relatively recent times."

他說：「我們發現的事物相當令人驚訝。許多人認為年代十分久遠的鋯石不可能在撞擊坑中形成，但現在我們知道其實它們可以。對於這些小傢伙我們還有許多尚未完全了解的地方，但現在看起來我們可以將地球早年的故事拼湊得更加完整。我們的發現跟現行的想法相當符合，認為早期地球飽受小行星的頻繁轟炸，與較為近期相比頻率高出許多。」

Gavin Kenny recently travelled to the annual Lunar and Planetary Science Conference (LPSC) in Houston, Texas, to present these findings to the space science community.

Gavin Kenny近日前往於休士頓舉行的年度月球和行星科學會議，向天文學社群發表他們的發現。

He added: "There was a lot of enthusiasm for our findings. Just two years ago a group2 had studied the likely timing of impacts on the early Earth and they suggested that these impacts might explain the ages of the ancient zircons. They were understandably very happy to see that the chemistry of the zircons from the Canadian impact crater matched the oldest crystals known to man."

他補充說：「有很多人對我們的新發現抱持著熱切關注。就在兩年前有另外一個團隊研究了同樣形成於早期地球，年代相近的撞擊坑，並提出這些撞擊事件或許可以用來解釋遠古鋯石的年代。可以想見他們會很樂意看到從加拿大的撞擊坑中取得的鋯石，其化學成分跟這些人類所知最古老的晶體竟然如此吻合。」

引用自：Trinity College Dublin. "Origin of Earth's oldest crystals." ScienceDaily. ScienceDaily, 28 April 2016. 

在引發地震的過程中雨水或許扮演了重要腳色

原文網址：www.sciencedaily.com/releases/2016/04/160427094859.htm

Rainwater may play an important role in process that triggers earthquakes

在引發地震的過程中雨水或許扮演了重要腳色

It's the rain's Fault

都是雨水惹的禍(斷層，兩者英文皆為fault)

Rainwater may play an important role in the process that triggers earthquakes, according to new research.

根據新的研究顯示，在引發地震的過程中雨水或許扮演了重要腳色。

Researchers from the University of Southampton, GNS Science (New Zealand), the University of Otago, and (Germany), identified the sources and fluxes of the geothermal fluids and mineral veins from the Southern Alps of New Zealand where the Pacific and Australian Plates collide along the Alpine Fault.

來自南安普敦大學、紐西蘭地質與核子科學研究所、奧塔哥大學以及德國波茨坦地質科學研究中心的研究人員，發現了紐西蘭南阿爾卑斯山脈的地熱流體和礦脈的來源與流量。紐西蘭的阿爾卑斯斷層為太平洋板塊跟印澳板塊聚合碰撞之處。

From careful chemical analyses, they discovered that fluids originating from the mantle, the layer below Earth's crust, and fluids derived from rainwater, are channelled up the Alpine Fault.

經過審慎的化學分析之後，他們發現源自地殼下方的地函流體以及從降雨而來的液體，會在阿爾卑斯斷層中彼此連通。

By calculating how much fluid is flowing through the fault zone at depth, the researchers showed for the first time that enough rainwater is present to promote earthquake rupture on this major plate boundary fault.

經由計算會有多少的液體流經斷層帶深部後，研究人員首次呈現出在這條大型板塊邊界斷層帶中，具有相當含量的雨水能夠促使斷層破裂並產生地震。

Lead researcher Dr Catriona Menzies, from Ocean and Earth Science at the University of Southampton, said: "Large, continental-scale faults can cause catastrophic earthquakes, but the trigger mechanisms for major seismic events are not well known. Geologists have long suspected that deep groundwaters may be important for the initiation of earthquakes as these fluids can weaken the fault zones by increasing pressures or through chemical reactions.

此篇研究的第一作者，南安普敦大學的海洋和地球科學博士Catriona Menzies說：「大型斷層帶可能會引起毀滅性的地震，但我們對於大型地震的觸發機制仍未具有全面性的了解。地質學家長久以來便猜測深層地下水對地震的引發而言相當重要。這是因為液體會增強水壓或是產生化學反應而弱化斷層帶。」

"Fluids are important in controlling the evolution of faults between earthquake ruptures. Chemical reactions may alter the strength and permeability of rocks, and if enough fluid is present at sufficiently high pressures they may aid earthquake rupture by 'pumping up' the fault zone."

「斷層在一次次破裂而引發地震的演化過程中，液體具有相當重要的控制地位。化學反應或許會改變岩石的強度以及滲透性，另外，若有相當多的液體在斷層帶中而產生夠高的水壓，這些液體或許能將其『抬起』而助長地震破裂發生。」

The Alpine Fault is a major strike-slip fault, like the San Andreas, that fails in very large (Magnitude 8+) earthquakes around every 300 years. It last ruptured in 1717 AD and consequently it is under intense scientific scrutiny because it is a rare example of a major fault that is late in the strain-build up before rupture.

阿爾卑斯斷層跟聖安地列斯斷層一樣是條大型平移斷層。它大約每300年就會發生一次相當大型(規模8以上)的地震，而上一次破裂發生在西元1717年。因為如此，它成為可能正在破裂邊緣，應力正不斷累積的罕有大型斷層例子，使得現在有許多科學監測活動正在進行。

Dr Menzies said: "We show that the Alpine Fault acts as a barrier to lateral fluid flow from the high mountains of the Southern Alps towards the Tasman Sea in the west. However, the presence of mantle-derived fluids indicates that the fault also acts as a channel for fluids, from more than 35 km depth, to ascend to the surface.

Menzies博士說：「我們的結果顯示出地下水在從南阿爾卑斯的高山地區往西方的塔斯曼海側向流動時，阿爾卑斯斷層具有阻斷的作用。然而，斷層中具有源自地函的流體的這件事指出，它同時也可以作為液體流通的管道。來自深度超過地下35km處的液體，能夠經此而上升至地表。」

"As well as mantle derived fluids, our calculations indicate that 0.02-0.05 per cent of surface rainfall reaches around six kilometres depth but this is enough to overwhelm contributions from the mantle and fluids generated during mountain-building by metamorphic reactions in hot rocks. This rainwater is then focused onto the fault, forced by the hydraulic head of the high mountains above and the sub-vertical fluid flow barrier of the Alpine Fault."

「除了來自地函的液體之外，我們的計算指出地表的降雨有百分之0.02至0.05可以到達地下6公里深。即使如此，這些量已遠遠超過地函來的液體，以及在造山運動時熾熱岩石經由變質作用而產生的液體。在上方高山造成的水頭，以及近乎垂直的阿爾卑斯斷層作為液體流動的屏障作用下，這些雨水會集中於斷層上。」

Funding for this research, published in Earth and Planetary Science Letters, was provided by the Natural Environmental Research Council (NERC), Deutsche Forschungsgemeinschaft, and GNS Science (New Zealand).

此篇刊登於期刊《地球和行星科學通訊》的研究，資金來自於自然環境研究委員會、德國研究學會和 紐西蘭地質與核子科學研究所。

引用自：University of Southampton. "Rainwater may play an important role in process that triggers earthquakes." ScienceDaily. ScienceDaily, 27 April 2016.