評論
打印
When Continents Collide: The History Of Our Planet
大陸相撞：我們星球的歷史
It was one of the Earth's momentous times. Continents collided. Volcanoes erupted. Ocean currents shifted. Species ran amok.
這是地球意義非凡的時刻之一。大陸板塊碰撞，火山噴發，洋流變化，各種物種橫行。
Twenty million years ago, North and South America were arranged in nearly the same positions as they are today. The big difference being, they were separated by a deep open channel called the Central American Seaway. There was no Panama and no need for a Panama Canal because there was clear sailing from the Atlantic to the Pacific.
兩千萬年前，南北美洲與今天相比位置相差無幾。最大的迥異之處在于，它們被一條稱作中美航道的深邃廣闊的海峽分開。當時沒有巴拿馬，也沒有巴拿馬運河存在的必要，因為當時有從大西洋到太平洋的暢通的航道。
But the Earth is a geologically active planet with shifting crustal plates. During the time period between twenty and three million years ago, the Pacific Plate collided with the Caribbean Plate, pushing magma to the surface to make islands in the sea, and eventually creating a land bridge between the two continents. The movement not only changed the land, it disrupted ocean currents, opened a door to species migrations and probably altered the world's climate.
但地球是一個地殼板塊不停運動，地質十分活躍的星球。在兩千萬年前到三千萬年前的這段時間里，太平洋板塊與加勒比海板塊發生碰撞，使得巖漿噴發出地表在海 洋中形成島嶼，并最終形成了連接上述兩塊大陸的陸地橋梁。這一運動不光改變了陸地，同時也改變了洋流，為物種遷移提供條件，并很可能改變了地球的氣候。
When the land bridge closed, equatorial waters could no longer mix. The Atlantic became saltier and the Pacific more dilute, creating a gradient that moves water in a giant loop around the globe today. Warm Atlantic water that used to pass through the gap moved northward, becoming the Gulf Stream. Scientists believe these changes created a warmer Europe and contributed to our recent cyclic ice ages.
當陸地橋梁合攏的時候，赤道附近的水域無法再相通。大西洋變得鹽度更大，而太平洋恰恰相反，這就形成梯度，成為今天的全球洋流大循環。溫暖的大西洋海水之 前流經海峽，如今只能向北流動，形成墨西哥灣暖流。科學家相信這些變化使得歐洲更加溫暖，并影響了我們最近一次周期性冰河世紀的到來。
The land bridge also opened the way for species to cross from one continent to the other. Deer, horses, raccoons, bears and the camel ancestors of llamas moved south across the bridge. Anteaters, porcupines, opossums and armadillos moved north.
陸地橋梁同時也為物種在大陸之間的遷移創造條件。鹿，馬，浣熊，熊和美洲駝的駱駝祖先通過這座“橋”來到南美洲。食蟻獸、豪豬、負鼠、犰狳 則一路向北。
Unfortunately, many large South America species couldn't compete with the North American animals and became extinct, changing the ecology of an entire continent.
不幸的是，許多大型的南美洲物種無力同北美洲遷移過來的動物競爭，從而滅絕，這改變了整個大陸的生態系統。
