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.

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