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  • Once upon a time,

    很久很久以前

  • South America lived harmoniously alongside Africa

    南美洲就祥和的靠在非洲旁邊

  • until a crack in the Earth

    直到地球的一個裂縫

  • drove the two continents apart.

    將兩大洲分離

  • This breakup began about 200 million years ago

    這裂縫始於2億年前

  • during the separation of the supercontinent

    超級大陸分離期

  • known as Pangaea.

    這個超級大陸也叫盤古大陸

  • Their proximity back then

    當初兩大洲的鄰近位置

  • explains why the same plant fossils and reptile fossils,

    可以解釋為何某些相同植物化石和

  • like the Mesosaurus,

    諸如中龍類的爬行類動物的化石

  • can be found on the South American east coast

    同時分佈在南美洲的東岸

  • and African west coast.

    和非洲的西岸

  • However, this evidence does not account forhow the continents moved apart.

    然而這項證據並不能

  • For that, we'll need to take a close look

    顯示兩大洲的分裂方式

  • at the earth below our feet.

    因此,我們必須更仔細的觀察

  • Though you may not realize it,

    我們腳下的陸地

  • the ground below you is traveling across the Earth

    或許你沒發現

  • at a rate of about 10 cm/year,

    你腳底下的陸地正在地球表面移動

  • or the speed at which your fingernails grow.

    並以每年10公分的速度在移動

  • This is due to plate tectonics,

    相當於你指甲生長的速度

  • or the large-scale movement of Earth's continents.

    這些移動是因為板塊的構造

  • The motion occurs within the top two layers of the Earth's mantle,

    或是地球各大洲劇烈的移動所造成的

  • the lithosphere and asthenosphere.

    這些移動發生於地幔的最上兩層:

  • The lithosphere, which includes the crust and uppermost mantle,

    岩石圈和軟流圈

  • comprises the land around you.

    岩石圈

  • Beneath the lithosphere

    包含了地殼和地涵的上層

  • is the asthenosphere

    構成了你周遭的陸地

  • the highly viscous but solid rock portion of the upper mantle.

    岩石圈底下

  • It's between 80 and 200 km below the Earth's surface.

    便是軟流圈

  • While the asthenosphere wraps around the Earth's core as one connected region,

    軟流圈具有高度的黏性,亦是上部地幔的固體石頭部分

  • the lithosphere is separated on top into tectonic plates.

    他的深度介於地球表面下方 80 至 200 公里之間

  • There are seven primary tectonic plates

    軟流圈以一個完整的形式包覆地核的外圍

  • that compose the shape of the planet we know today.

    然而,岩石圈卻在上方分開成一塊塊的板塊

  • Like the other smaller tectonic plates,

    我們現在所知道的地球

  • the primary plates are about 100 km thick

    是由七塊主要的板塊所構成

  • and are composed of one or two layers:

    這些主要板塊的厚度和其他較小的板塊一樣

  • continental crust and oceanic crust.

    約莫是100公里厚

  • Continental crust forms the continents

    而這些板塊是以單層或雙層的形式組成的

  • and areas of shallow water close to their shores,

    稱為「大陸地殼或海洋地殼」

  • whereas oceanic crust forms the ocean basins.

    大陸地殼形成了各大洲

  • The transition from the granitic continental crust

    以及岸邊的淺水地帶

  • to the basaltic oceanic crust

    而海洋地殼則構成了海洋盆地

  • occurs beyond the continental shelf,

    花崗岩質的大陸地殼和

  • in which the shore suddenly slopes down

    玄武岩質的海洋地殼的分界線

  • towards the ocean floor.

    位於大陸棚的後方

  • The South American Plate is an example

    在大陸棚的後方

  • of a tectonic plate made of two crusts:

    海岸急速下降到海底

  • the continent we know from today's map

    南美洲板塊便是一例

  • and a large region of the Atlantic Ocean around it.

    由兩個地殼組成的板塊

  • Collectively comprising the lithosphere,

    其中一個是我們所知道的南美洲

  • these plates are brittler and stiffer

    另一個,則是周圍一部份的大西洋

  • than the heated, malleable layer of the asthenosphere below.

    這些板塊包含了岩石圈

  • Because of this,

    且相較於下方可塑性強的軟流圈

  • the tectonic plates float on top of this layer,

    更為堅硬和脆弱

  • independently of one another.

    因此

  • The speed and direction in which these tectonic plates move

    這些板塊比差分開的

  • depends on the temperature and pressure

    漂浮在軟流圈之上

  • of the asthenosphere below.

    這些板塊

  • Scientists are still trying to nail downthe driving forces behind this movement,

    根據下方軟流圈的不同壓力和溫度

  • with some theories pointing towards mantle convection,

    而有不同的移動方向和移動速率

  • while others are examining

    科學家仍試圖確定

  • the influence of the Earth's rotation

    促使這些運動發生的作用力

  • and gravitational pull.

    有些理論將矛頭指向地幔對流

  • Though the mechanics have not been sorted out,

    而有些則是繼續觀察

  • the scientific community agrees

    地球的轉動和引力

  • that our tectonic plates are moving and have been for billions of years.

    是否為這些作用力的源頭

  • Because these plates move independently,

    雖然當中的原理尚未被分析出來

  • a fair amount of pushing and pulling

    但是科學界仍一致同意

  • between the plates occurs.

    我們所身處的板塊已經流動了幾十億年了

  • The first type of interaction

    由於這些板塊是獨自的運動

  • is a divergent boundary,

    因此極為龐大的交互作用

  • in which two plates move away from one another.

    便發生於這些板塊之間

  • We see this in the Mid-Atlantic Ridge

    第一種交互作用力

  • between South America and Africa.

    是使相鄰兩板塊相離的斥力

  • The next interaction is when two plates collide,

    是使相鄰兩板塊相離的斥力

  • known as a convergent boundary.

    我們在南美洲和非洲之間的

  • In this instance, the land is pushed upward

    大西洋中脊便可看見此現象

  • to form large mountain ranges,

    下一個交互作用力發生於兩板塊碰撞時

  • like the Himalayas.

    又被稱為是聚合力

  • In fact, the Indian Plate is still colliding

    在這撞擊的一瞬間

  • with the Eurasian Plate,

    陸地被往上推擠並形成山脈

  • which is why Mount Everest

    而喜馬拉雅山便是一例

  • grows one cm/year.

    其實印度板塊現仍正與歐亞板塊

  • Finally, there's the transform boundaries,

    發生擠壓

  • where two plates scrape past one another.

    這也是為什麼珠穆朗瑪

  • The grinding of the transform boundary

    以每年1公分的速率生長著

  • leads to many earthquakes,

    最後則是兩板塊

  • which is what happens

    平行擦過的剪力

  • in the 810 mile-long San Andreas Fault.

    剪力的摩擦作用

  • The moving Earth is unstoppable,

    造成很多的地震

  • and, while a shift of 10 cm/year may not seem like a lot,

    而長 810 英里聖安地列斯斷層

  • over millions of years our planet will continue

    便是一例

  • to dramatically change.

    地球的移動是不會停止的

  • Mountains will rise,

    雖然每年10公分的些微變化看似不是很多

  • shorelines will recede,

    但是幾百萬年後的地球

  • islands will pop up.

    仍會有著巨大的改變

  • In fact, one projected map shows

    山脈會一個個隆起

  • the cities of Los Angeles and San Francisco

    海岸線會倒退

  • on top of each other.

    島嶼一個個出現

  • Maybe South America and Africa

    事實上 一個虛擬地圖顯示

  • will come together again, too.

    洛杉磯和舊金山

  • Only time will tell.

    相疊在一起的樣貌

Once upon a time,

很久很久以前

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B2 中高級 中文 美國腔 TED-Ed 板塊 地殼 南美洲 地球 大陸

【TED-Ed】不斷在運動的地球 (The Pangaea Pop-up - Michael Molina)

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    Kevin Tan 發佈於 2018 年 01 月 12 日
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