跟读练习: The World Before Plate Tectonics - 通过YouTube学习英语口语
C1
Around 2 billion years ago, Earth was a very different place.
74 句
如果句子过短或过长，请点击 Edit 进行调整。
1
Around 2 billion years ago, Earth was a very different place.
2
Pretty much everything was more extreme than it is today, from ocean chemistry, to slimy life on land, to the position of landmasses. Things were generally… a little weird.
3
The oceans would have been inhospitable to most animal life today, because they were very low in oxygen but really high in sulfur.
4
Meanwhile, on land, there wasn’t much life to speak of, except for microbial organisms, like cyanobacteria and possibly lichens.
5
Even the temperature inside the Earth was more extreme than it is today.
6
But the world for these early living things was also kind-of...boring.
7
The climate was remarkably stable; there wasn’t much glacial activity, and the sun was 5 to 18% less powerful than it is today.
8
Even the rocks under the microbes were fairly stable.
9
Modern plate tectonics, the movement of rock plates on top of Earth’s mantle, hadn’t gotten started yet.
10
The mantle was just too hot, so it bound the continental plates together into a supercontinent.
11
And the plates were flimsy and thin.
12
Because this time in Earth’s history was so stable, geologists once called it the Boring Billion - the billion years from about 1.8 billion to 800 million years ago.
13
But the fact is, this period was anything but boring. In fact, it set the stage for our modern version of plate tectonics - and probably for the rise of life as we know it.
14
Today, Earth’s plate tectonics cycle is active.
15
The plates move around, forming mountains as they smash together, shallow seas when they rift apart, and even volcanoes when they slide under each other.
16
Plate movement is responsible for some of Earth’s most noticeable features, including the Himalayas, the East African Rift valley, and the Pacific Ring of Fire.
17
They’re so important that it’s almost hard to imagine what the planet looked like before plate tectonics.
18
To figure that out, we have to go back to when Earth was first settling down from its formation, back at the end of the Archean Eon, almost 3 billion years ago.
19
Unfortunately for geologists, a lot of the rock record has been continuously recycled and destroyed through subduction, where one slab of rock slides under another and dives down into the mantle, where it melts.
20
That means evidence of the oldest rocks is really limited, because they’ve been ripped apart, smashed together, and eroded away.
21
But the Archean rocks that did manage to survive on Earth’s surface are spread out all over the world, in places like North America, Australia, Africa, and Eastern Europe - and some are more than 3 billion years old!
22
And that presented a puzzle to geologists who wanted to find out when modern plate tectonics started, and what it looked like.
23
Since subduction is one of the main drivers behind today’s plate tectonics, they looked for evidence of subduction as a sign of the beginning of ancient plate tectonics.
24
So scientists slowly pieced together evidence from the few surviving rock slabs, as well as computer models, to start to understand the Archean.
25
You see, geologists can look at minerals in a rock to figure out how deep a piece of land went into Earth’s interior, and how hot it got.
26
And they found that starting around 2.78 billion years ago, in the late Archean, there is solid evidence that Earth’s lithosphere was busy.
27
There were supercontinents breaking apart and forming, mountain-building episodes, and metamorphism, where rocks are transformed by high heat and pressure.
28
Now, that certainly sounds a lot like plate tectonics, but does it really count as the first example of plate tectonics? Well, geologists have opinions about that.
29
It didn’t work the same way as the modern version of plate tectonics because Earth’s mantle was hotter than it is today -- about 250 degrees celsius hotter.
30
The mantle reached peak temperatures in the Archean, and has been slowly cooling since then. 2.8 billion years ago, the mantle was still holding on to more heat than it is today.
31
Those high mantle temperatures made the crust thin, weak, and easy to deform - like cookies straight out of the oven. The metamorphic rock record shows that if there was subduction into the mantle, the sinking crust stayed pretty shallow, unlike today.
32
It was a different “flavor” of subduction. That’s why some geologists don’t think this really counts as the first evidence of plate tectonics.
33
But these early movements of the lithosphere helped separate the crust into plates.
34
Those plates crammed together in one spot, leading to the formation of the supercontinent Nuna by 1.8 billion years ago.
35
Welcome to the so-called Boring Billion.
36
Remember, all of this was over a billion years before the Cambrian explosion. So with the exception of some microbes, there was no life on land: it was confined to the ocean.
37
And the ocean was very different than it is now.
38
2 billion years ago, it’s likely that most of the ocean was very low in oxygen.
39
But what it did have in abundance was hydrogen sulfide. And by 1.6 billion years ago that combination created a condition known as euxinia, which is toxic to most eukaryotes -- organisms that have an enclosed nucleus in each cell.
40
But the prokaryotes, simpler life forms that don’t have an enclosed nucleus, made the best of their strange environment.
41
Microscopic life forms like archaea were perfectly happy. And so were bacteria, like cyanobacteria, which were photosynthetic and could metabolize the abundant sulfur in the ocean.
42
Also there were purple and green sulfur bacteria, which are brightly-colored photosynthetic microbes that can form squishy mats in aquatic environments.
43
They sound like they belong in a scifi movie, but they’re very real, and still around today.
44
So most of the life found in the Boring Billion was prokaryotic. And with all this sulfur in the environment, researchers think this period was the stinkiest time on Earth!
45
But to geobiologists - scientists who study the interactions between the biosphere and Earth’s physical processes - this period was never boring, because it marked the beginning of complex eukaryotic life.
46
For example, in China there are rock formations that contain fossils of eukaryotes that date back 1.7 billion to 1.4 billion years ago!
47
The majority of these organisms lived in water, including protists and other early eukaryotes, So life on the early supercontinent, with limited plate movement, was doing okay. But it was still all microbes and slimy mats, trying to survive in sulfur-rich water.
48
So how did we get from there to here, or even to the Cambrian explosion?
49
Well, life needed Earth to shake things up.
50
And that didn’t happen in the Boring Billion, at least not enough to make a huge difference.
51
The old flavor of softer, squishier plate tectonics continued, with minor, shallow subduction around Nuna and the next supercontinent, Rodinia.
52
Plates on the outside of the supercontinent were mostly stagnant, but started sinking into the mantle, which was beginning to cool.
53
Then, probably no later than 750 million years ago, during the breakup of Rodinia, the cooler mantle meant that the plates weren’t continuously melting and sticking together.
54
Separate slabs of rock could interact, forming rift valleys and subduction zones.
55
Some geologists say this was the beginning of modern plate tectonics, because they have clear evidence of deep subduction.
56
For example, they’ve found metamorphic minerals that could only have formed at high pressure, deep in Earth’s mantle.
57
And that would’ve been impossible under the earlier type of plate tectonics, when the plates stayed shallower and softer.
58
So, experts are still debating whether the earlier period of subduction really “counts” as the beginning of plate tectonics. And some say that there was even older evidence of tectonic movement, as far back as 4 billion years ago!
59
But there’s one thing that they all agree on: plate tectonics helped shape the planet into the habitable world we know today.
60
As supercontinents like Rodinia broke up into separate plates, the slabs jostled each other, smashing together or moving apart.
61
When two plates separate from each other, oceanic ridges form - underwater mountain ranges where hot magma constantly comes out and cools, becoming part of the plates. This process is called seafloor spreading.
62
Today, seafloor spreading is occuring in several ocean basins, and oceanic ridges are some of the best places to find hydrothermal activity, where water interacts with hot, fresh, ocean crust.
63
These vents are hotspots for biodiversity, especially because they are so rich in iron and silica, important fertilizers for many life forms.
64
And moving plates can constantly create new habitats and destroy others, which promotes rapid diversification of life.
65
Researchers have shown that biodiversity increases really fast when there’s more continental fragmentation.
66
Plus, the arrangement of the continents can impact ocean circulation, climate, carbon cycling, and many of the other processes that help shape life on Earth.
67
So it turns out that the Boring Billion wasn’t really boring at all! Earth was just settling down and getting ready for its next big move.
68
And today, we’re the only planet known to have this type of plate tectonics.
69
So, while the movement of continental plates can be destructive, it might’ve also been pretty important for pushing life past the squishy microbe stage to create the lush, complex diversity of living things that we know today.
70
If you’re a fan of Eons, then you’ll love the new PBS three-part natural history series: Prehistoric Road Trip!
71
Get ready for an epic adventure through dinosaur country to discover the mysterious creatures and bizarre ecosystems that have shaped Earth as we know it. With popular YouTube personality Emily Graslie as host and guide, you’ll travel thousands of miles to visit some of the most active and dynamic fossil sites in the world.
72
Prehistoric Road Trip premieres Wednesdays, June 17th-July 1st at 10/9c. Streaming is available across platforms, including pbs.org and the video app – find out more at the link in the description.
73
No-so-boring high fives to this month’s Eontologists: Lucan Curtis-Mahoney, Sean Dennis, Jake Hart, Jon Davison Ng, Patrick Seifert, and Steve! Become an Eonite at pateron.com/eons and get exclusive access to our Discord and the Eonites Only Podcast - hosted by me!
74
And thank you for joining me today in the Konstantin Haase studio. Subscribe at youtube.com/eons for more adventures in deep time.
下载应用
AI 为你说出的每个句子打分
TRENDING
热门
上下文与背景
在这段视频中，讲述了地球在大约20亿年前的状况，以及板块构造运动如何影响地球的演变。尽管这一时期被称为“无聊的亿年”，但实际上，它为现代板块构造的形成铺平了道路。通过了解这些历史背景和科学概念，英语学习者可以获得更丰富的词汇和表达，以便在日常交流中使用。
日常交流中的五个重要短语
- 地球的历史（The history of Earth）
- 生命的起源（The origin of life）
- 板块运动（Plate movement）
- 古老的岩石（Ancient rocks）
- 微生物的生存（Survival of microorganisms）
逐步影子跟读指南
要提高你的英语发音，通过看YouTube学英语的视频进行影子跟读是一个有效的方式。以下是如何使用这段视频进行英语影子跟读的简单步骤：
- 观看视频：首先，完整观看视频，理解叙述的内容和科学概念。
- 分段播放：将视频分成小段落，反复播放每段。听懂后再尝试复述。
- 跟随模仿：用你的声音来模仿讲解者的语调和发音。此时可以集中在提升发音质量，使用提高英语发音的技巧。
- 渐进式练习：随着练习的深入，逐渐提高跟读的速度，最终要能够流畅地复述原内容。
- 利用资源：使用字典查找不明白的单词，或观看其他视频以了解更多相关背景知识，进行更深层次的学习。
通过这些方法，结合shadowspeak的练习和探索，你将会在英语口语表达和理解方面取得显著的进步！
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。