本篇文章共分 4 段，將大陸漂移理論從魏格納的提出、霍姆斯的補充、全球地形上的證據，到古氣候所提供的證據一一加以說明陳述，以支持其重要性。

本篇考題英文原文與對應之中文翻譯整理如下。練習作答解題時若有對語意不清楚之處，請仔細查閱對照，以提升閱讀理解能力。

Alfred Wegener's Theory of Continental Drift 阿爾弗雷德-魏格納的大陸漂移理論

1. 大陸漂移理論的提出

   In 1912, the German geologist Alfred Wegener proposed that Earth's continents are mobile rafts of lighter crust that have shifted over time by plowing their way through the denser crust of the oceans. The theory, called continental drift, was partly motivated by the apparent fit, like puzzle pieces, of the coastlines of South America and Africa. Wegener first presented his theory of continental drift at a meeting and in a paper, and then as a book, The Origin of Continents and Oceans, published in 1915. He continued to write updated versions of this work until his death in an ill-fated expedition to Greenland in 1930. Wegener maintained that Earth is composed of concentric shells of increasing density from crust to core. The outermost shell is not continuous but made of continental blocks of lighter rock called sial (an acronym for silica- and aluminum-rich rock) floating in the denser sima (silica- and magnesia-rich rock) underlying the oceans. All the continents had been joined in the supercontinent of Pangaea. As the continent broke up, the pieces moving apart left bits behind, explaining the presence of nonvolcanic islands and island chains, according to Wegener. Where the moving pieces collided, mountains formed. They were thrust up either by the plowing of the continents through the sima, as in the case of the Andes, or by the colliding of two blocks of sial, as in the case of the Himalayas. As for the force driving continental drift, Wegener initially invoked Polfluchtkraft—a force causing flight from the poles as a result of Earth’s rotation—and later the tidal force resulting from the gravitational attraction between Earth and the Moon and Sun.

   1912 年，德國地質學家阿爾弗雷德．魏格納提出，地球上的大陸是由較輕的地殼組成的移動筏子，隨著時間的推移，它們在海洋較密的地殼中像犁般移動而發生了變化。這一理論被稱為大陸漂移，其部分動機是南美洲和非洲的海岸線像拼圖一樣明顯的吻合。魏格納首先在一次會議上和一篇論文中提出了他的大陸漂移理論，後來又寫成了一本書，《大陸和海洋的起源》，於 1915 年出版。他繼續撰寫這部作品的更新版本，直到 1930 年他在格陵蘭島的探險中不幸去世。魏格納認為，地球是由從地殼到地核的密度不斷增加的同心殼組成的。最外層的殼不是連續的，而是由被稱為矽鋁層 (sial)（富含矽和鋁的岩石的縮寫）的較輕岩石構成的大陸塊漂浮在海洋下面的密度較高的矽鎂層 (sima)（富含矽和鎂的岩石）所組成。所有的大陸都在盤古大陸這個超級大陸上結合在一起。據魏格納說，隨著大陸的解體，移動的碎片留下了一些更小的碎片，解釋了非火山島和島鏈的存在。在這些移動的碎片碰撞的地方，形成了山脈。它們要麼是被大陸犁過西瑪而推起，如安第斯山脈的情況，要麼是被兩塊西瑪的碰撞而推起，如喜馬拉雅山脈的情況。至於驅動大陸漂移的力量，魏格納最初援引了 Polfluchtkraft—一種由於地球自轉而導致從兩極飛出的力量，後來又援引了地球與月球和太陽之間的引力所產生的潮汐力。

2. 霍姆斯的補充

   One of the most influential geologists to join the mobilist camp, as the drifters school became known, was Arthur Holmes. Holmes recognized the importance of radioactive heat—which had recently been discovered—and realized that there must be a mechanism to remove it from Earth’s interior. That mechanism, he argued, is convection—the rising of less dense material and the sinking of more dense material. He went on to propose that the mantle (the part of Earth’s interior below the outer crust and above the core) convects in large, circulating patterns, and that this motion carries the continents across Earth’s surface. He also related crustal movement and mantle convection to the evolution of mountain belts. Wegener adopted Holmes's mechanism in the last rendition of his theory. Holmes, for his part, presented his grand concept of a dynamic Earth in his influential and popular text Principles of Physical Geology, published in 1944.

   加入移動論陣營，也就是一般人所熟知的漂移學派，的最有影響力的地質學家之一是阿瑟．霍姆斯。霍姆斯看出最近發現的放射性熱的重要性，並意識到一定有一種機制可以將其從地球內部移出。他認為，這種機制就是對流—亦即密度較小的物質上升，密度較大的物質下沉。他進一步提出，地幔（地球內部低於地殼、高於地核的部分）以大型的循環模式對流，這種運動帶著大陸穿過地球的表面。他還將地殼運動和地幔對流與山脈帶的演變聯繫起來。魏格納在他的理論的最後一個版本中採用了霍姆斯的機制。霍姆斯則在他 1944 年出版的有影響力的通俗讀物《物理地質學原理》中提出了他關於動態地球的宏偉概念。

3. 漂移理論的地理證據

   Although it was eventually supplanted by the theory of plate tectonics, Wegener’s theory of continental drift influenced science because it explained disparate observations, because it was placed in the context of existing theories, and because it offered a coherent view of Earth's evolution. For example, Wegener showed not only that the coastlines on opposite sides of the Atlantic fit together, but that geologic features on the different continents fit as well. He asserted that the Appalachians, which can be traced northward through the Canadian Maritime Provinces, match the Caledonian Mountains in Scotland and Norway. He marshaled evidence from the distributions of fossil and living species to argue that land bridges joining continents were less likely than a single continent. The example commonly cited is that of Mesosaurus, a shoreline scavenger reptile that lived in the Permian period and is found as fossils in rocks on both sides of the South Atlantic Ocean. Mesosaurus was thought not to be a great swimmer, certainly not able to cross an ocean.

   雖然它最終被板塊構造理論所取代，但魏格納的大陸漂移理論影響了科學，因為它解釋了不同的觀察結果，因為它被置於現有理論的背景中，因為它對地球的演變提供了一個連貫的觀點。例如，魏格納不僅證明大西洋兩岸的海岸線形狀兩相匹配，而且不同大陸上的地質特徵也密切匹配。他斷言，阿帕拉契山脈可以通過加拿大濱海省向北追溯，與蘇格蘭和挪威的喀里多尼亞山脈相匹配。他從化石和生物物種的分佈中收集證據，認為連接各大陸的陸橋比單一大陸的可能性要小。通常引用的例子是中龍，這是一種生活在二疊紀的海岸清道夫爬行動物，在南大西洋兩岸的岩石中都能找到化石。中龍被認為不擅長游泳，當然不可能穿越海洋。

4. 漂移理論的氣候證據

   Wegener also found supporting evidence in ancient climates. Mounting observations indicated that the past climate of many regions was much different from the present climate. In the tropics, geologists had found sand and gravel left by ancient glaciers, and in rainy regions they had located prehistoric deserts. Then there was the discovery, by a British expedition, of plant fossils only 600 kilometers (370 miles) from the South Pole. Particularly puzzling was evidence suggesting that widely different climates in different regions had occurred at the same time, so one could not account for different climates by claiming simply that the whole of Earth was once hotter or once cooler than now. Wegener solved this dilemma by showing that observations of paleoclimate could be explained if the positions of the continents had shifted relative to those of the poles.

   魏格納還在古代氣候中找到了支持證據。大量的觀察顯示，許多地區過去的氣候與現在的氣候有很大的不同。在熱帶地區，地質學家發現了古代冰川留下的沙子和礫石，在多雨地區，他們找到了史前沙漠。然後，一組英國探險隊發現了距離南極僅 600 公里（370 英里）的植物化石。特別令人困惑的是，有證據指出，不同地區大不相同的氣候是在同一時間發生的，因此人們不能簡單地聲稱整個地球曾經比現在更熱或更冷，來解釋不同的氣候。魏格納解決了這個難題，他指出，如果大陸的位置相對於兩極的位置發生了變化，就可以解釋古氣候的觀察。