The Pangaea Pop-up - Michael Molina

泛大陆的出现 - 迈克尔·莫利纳

翻译人员: 静宁 张 校对人员: Chenwei CAO

Once upon a time,

很久以前

South America lived harmoniously alongside Africa

南美洲和非洲紧邻着

until a crack in the Earth

直到地球上出现一道裂缝

drove the two continents apart.

把两个大陆分开

This breakup began about 200 million years ago

这次分裂发生在大约 2 亿年前

during the separation of the supercontinent

当时被称为泛大陆的超级大陆

known as Pangaea.

开始分裂

Their proximity back then

两块大陆曾紧紧相邻

explains why the same plant fossils and reptile fossils,

解释了为什么相同的植物化石和爬行动物化石

like the Mesosaurus,

比如中龙化石

can be found on the South American east coast

会出现在南美东海岸

and African west coast.

和非洲西海岸

However, this evidence does not account

然而, 这个证据无法解释

for how the continents moved apart.

大陆是如何分离的

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

因此, 我们需要更加仔细地看看

at the earth below our feet.

我们脚下的地球

Though you may not realize it,

虽然你可能没有意识到

the ground below you is traveling across the Earth

但你脚下的陆地 正在地球上漂移

at a rate of about 10 cm/year,

大约以每年十厘米的速度漂移

or the speed at which your fingernails grow.

也就是你指甲生长的速度

This is due to plate tectonics,

这是由于板块构造

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

或大陆的大规模移动

The motion occurs within the top two layers

这种运动发生在

of the Earth's mantle,

地幔的最上面两层中

the lithosphere and asthenosphere.

也就是岩石圈和软流层

The lithosphere,

岩石圈

which includes the crust and uppermost mantle,

包括地壳和上地幔顶部

comprises the land around you.

也就是你脚下的陆地

Beneath the lithosphere

在岩石圈以下

is the asthenosphere

是软流层

the highly viscous but solid rock portion

它是上地幔中粘稠度高

of the upper mantle.

但又为固态岩石的部分

It's between 80 and 200 km

它在地表以下

below the Earth's surface.

80千米到200千米之间的地方

While the asthenosphere wraps around the Earth's core

软流层包裹着地核

as one connected region,

使之成为一个连续的整体

the lithosphere is separated on top

最上方的岩石圈

into tectonic plates.

被分为不同的板块

There are seven primary tectonic plates

如今我们知道 地球表面

that compose the shape of the planet we know today.

是由七个主要板块构成的

Like the other smaller tectonic plates,

和其他小板块一样

the primary plates are about 100 km thick

主要板块大约有100公里厚

and are composed of one or two layers:

由一或两层地壳组成：

continental crust and oceanic crust.

陆壳和洋壳

Continental crust forms the continents

陆壳构成陆地

and areas of shallow water close to their shores,

和靠近海岸的浅水地区

whereas oceanic crust forms the ocean basins.

而洋壳形成洋盆

The transition from the granitic continental crust

从花岗岩的陆壳到

to the basaltic oceanic crust

玄武岩质的洋壳的转变

occurs beyond the continentel shelf,

发生在大陆架以外的地方

in which the shore suddenly slopes down

在那里 海岸骤然

towards the ocean floor.

下降到洋底

The South American Plate is an example

南美洲板块就是这样一个

of a tectonic plate made of two crusts:

由陆壳和洋壳构成板块的例子：

the continent we know from today's map

我们从如今的地图中知道, 它由南美洲大陆

and a large region of the Atlantic Ocean around it.

和周围大部分的大西洋地区组成

Collectively comprising the lithosphere,

这些板块构成岩石圈

these plates are brittler and stiffer

比下面高温、粘稠的

than the heated, malleable layer of the asthenosphere below.

软流层更脆、更硬

Because of this,

正因为如此

the tectonic plates float on top of this layer,

构造板块互相独立的

independently of one another.

浮在软流层上

The speed and direction in which these tectonic plates move

这些板块移动的速度和方向

depends on the temperature and pressure

取决于下方软流层的

of the asthenosphere below.

温度和压强

Scientists are still trying to nail down

科学家们仍在努力研究

the driving forces behind this movement,

造成这一运动的驱动力是什么

with some theories pointing towards mantle convection,

一些理论认为是地幔的对流

while others are examining

而其他一些认为

the influence of the Earth's rotation

是由于地球自转

and gravitational pull.

还有引力作用的影响

Though the mechanics have not been sorted out,

虽然力学原因没有弄清

the scientific community agrees

但科学界一致同意

that our tectonic plates are moving

我们的构造板块在正移动

and have been for billions of years.

而且已经进行了数十亿年

Because these plates move independently,

因为这些板块各自移动

a fair amount of pushing and pulling

板块之间就会产生大量的

between the plates occurs.

推和拉的相互作用

The first type of interaction

其中第一种相互作用

is a divergent boundary,

是分离型板块边界

in which two plates move away from one another.

两个构造板块 向相反方向背离运动

We see this in the Mid-Atlantic Ridge

比如 南美洲和非洲之间的

between South America and Africa.

大西洋洋中脊就是这样

The next interaction is when two plates collide,

第二种相互作用类型是板块碰撞

known as a convergent boundary.

被称为 汇聚型板块边界

In this instance, the land is pushed upward

在这个例子中, 陆地被抬升

to form large mountain ranges,

形成大山脉

like the Himalayas.

比如喜马拉雅山

In fact, the Indian Plate is still colliding

事实上, 印度板块与欧亚板块

with the Eurasian Plate,

至今仍在对撞

which is why Mount Everest

这就是为什么珠穆朗玛峰

grows one cm/year.

每年升高一厘米

Finally, there's the transform boundaries,

最后一种类型, 是转换型板块边界

where two plates scrape past one another.

两个板块在水平方向相对滑动

The grinding of the transform boundary

这种转换型边界的摩擦

leads to many earthquakes,

造成了地震的频发

which is what happens

这就是发生在

in the 810 mile-long San Andreas Fault.

810 英里长的圣安德烈斯断层中的情况

The moving Earth is unstoppable,

地球的运动是不可阻挡的

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

虽然每年移动十厘米 看起来不大

over millions of years our planet will continue

而我们星球数百万年来的持续运动

to dramatically change.

将带来沧海桑田的变化

Mountains will rise,

山峦会上升

shorelines will recede,

海岸线会消退

islands will pop up.

岛屿会露出海面

In fact, one projected map shows

事实上, 一幅预期的地图显示

the cities of Los Angeles and San Francisco

洛杉矶和旧金山两个城市

on top of each other.

彼此将十分靠近

Maybe South America and Africa

也许南美洲和非洲

will come together again, too.

还会再次走到一起

Only time will tell.

只有时间能够证明