Shadowing Practice: There's a Giant Hole In Earth's History - Learn English Speaking with Video

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Hey, 42 here.

If you've ever found yourself flipping furniture as you search frantically for your car keys, you'll know how easy it is to misplace something.

Maybe you lost your phone, your wallet, or the will to live.

But of all these, the biggest mystery is how we lost a billion years of history.

This is far more serious than when you found your keys in the bread bin, because there's a colossal blank spot in our planet's past,

and nobody's quite sure where we put it.

To put things into perspective, a billion years is almost a quarter of Earth's existence

and yet there's a billion year gap in the fossil record that geologists call the Great Unconformity.

Let's dig a little deeper, shall we?

Speaking of which, if you ran outside right now and started to dig, you'd uncover older layers of rock the deeper you got.

First, you'd find an Alanis Morissette tape from the 90s.

Maybe a disco ball from the 70s.

But eventually, you'd excavate some Roman coins and other assorted artifacts.

So, why is it that both human and natural remains sink deeper into the Earth as time passes?

Well, the Earth's surface is constantly being littered with fine particles like sand and dust.

This sediment accumulates in an agonisingly slow process called deposition.

Then, in another process called cementation, these mineral particles gradually bind together until, a few million years later,

and sedimentary rock is formed.

Then, another layer of rock forms on top of that, then another, and another, and so on, until the ground beneath your feet is like a trifle.

A rock trifle with millions of layers made over millions of years.

And not a single one of them contains custard.

What a tragedy.

But during all this sedimentation and cementation, animals are doing their usual party trick of dying.

All the soft, squidgy bits get eaten or decomposed, but sometimes the harder bits, like bones, shell and husk, get covered in dust.

slowly succumbing to the sedimentation, thus becoming encased in rock.

Over time, water penetrates this rocky tomb, which dissolves the biological remains within.

Eventually, minerals fill that void and form a fossil, which of course is just a rock replica of the creature that once resided there.

Importantly though, that fossil is frozen in time, enshrined in the sedimentary rock from the era in which the animal lived.

Much of our understanding of the history of the planet

and life itself has come through studying the sequence of sedimentary rock layers and the treasures they've trapped through time.

Often the different layers, called strata, are clear and distinct, with each revealing something unique about the age it was formed in.

The stupendously fun pastime of studying strata is called stratigraphy

and one of its guiding principles is the law of superposition

which states that

if undisturbed the lower down the rock layer the older the rock not exactly rock it's science

but it does mean that generally

when you're looking at a cross section of geologic formations you

get a fairly neat picture of the passage of time but unfortunately history isn't so predictable.

Whilst new layers of sedimentary rock are being formed in one location, in another conditions can change, and sedimentation just stops.

Wind and water erosion can move particles elsewhere, effectively deleting part of a geologic record.

After a while, sedimentation might resume in that location, but these temporary interruptions will forever leave a gap in that rock's record,

and sometimes that gap, called a hiatus, can be millions of years long.

It's like hitting pause, rewind, and then record again whilst in a very long conversation.

In the final recording there will be missing parts that are irrecoverable

and if these parts are integral to the meaning of said conversation then the whole thing will no longer make any sense.

When these hiatuses happen it creates a noticeable difference in the angle, colour, and texture of the new rock that sits on top,

as can be seen here and here.

Geologists call this feature an unconformity.

It was Danish man Neil Steensen, considered the father of stratigraphy, who first sketched an unconformity.

back in 1669, but it was a Scottish farmer called James Hutton who discovered the first significant unconformity.

Whilst walking near Sicca Point in Scotland in 1787, he noticed a striking difference between the lower and upper rock formations,

and so he coined the name for it, Hutton's Unconformity.

If that name sounds a little rude to you, but you're not really sure why, join the club.

anyway the grayish lower layer of rock is made up of deep sea deposits from around 425 million years ago

but the reddish upper layer was deposited by rivers and streams about 345 million years ago

that's a hiatus of about 80 million years it was on the back of this discovery

that hutton helped develop some major theories about the movement of tectonic plates

and the forces that shaped the face of the earth.

Some geologists call Sicker Point a geologic shrine,

which tells you how incredibly strange both this formation and geologists actually are.

However, the most unusual unconformity was found in 1869, when John Wesley Powell was observing a strange mound.

Whilst traversing the Grand Canyon, he noticed a vertical rock formation butting up against horizontal formations.

Channeling the supreme creativity of his geologist predecessors, he named it Powell's Unconformity.

But since then, it's been more commonly referred to as Powell's Great Unconformity.

And there are two striking reasons why it's deserving of a great.

Firstly, the unconformity actually spans an entire continent, stretching across Laurentia, which is the name for the ancient heart of North America.

Secondly, many other unconformities had been unearthed around the world at this point, but they mostly represented small gaps, on a planetary scale at least,

maybe tens of millions of years.

But the smallest time gap between the two rock layers in the Great Unconformity is a modest 250 million years.

And the biggest is over 1 .2 billion years.

That's right, that missing piece of prehistoric pie sandwiched between these two unassuming

rock formations represents up to 1 .2 billion years of missing history.

And we have no idea where it went.

But there's so much more to this rocky weirdness.

Since Powell's grand discovery, a few more formations have been found all over the world

that have the same time period plucked from their record.

Together, we collectively refer to these as the Great Unconformity.

It's a mystery that spans the entire planet and over a billion years of missing knowledge.

Take the Grand Canyon example.

Here, the 525 million year old Cambrian era Tapiet Sandstone sits

snugly on top of the 1 .7 billion -year -old Visnu Basement rocks, dating back to the Precambrian era.

Like I said, a time gap of 1 .2 billion years.

Weird, right?

Scuttle over to the Ozark Plateau in Missouri, where we see a similar site.

500 million -year -old sandstone sits suspiciously atop 1 .4 billion -year -old granite,

representing a 900 -million -year hiatus.

For the sake of all that is igneous, what's the metamorphic heck is going on here?

Well, some have suggested a theory to explain the great unconformity, and it's called the Snowball Earth Theory.

It refers to a time during the Cryogenian period, around 650 million years ago,

when the Earth's surface was thought to be covered by glaciers and ice sheets, like a giant snowball.

Glasses are capable of causing erosion on a massive scale as they grind across landscapes.

And it's been estimated that they collectively removed two to three miles from the Earth's surface.

Basically, the Earth had its face exfoliated.

Now, do you remember me saying that the younger rocks

that sit atop the Great Unconformity all around the world date back to a period called the Cambrian period.

Well, what's really interesting here is that the Cambrian period was when the biggest explosion of life in our planet's history took place.

During a tiny timeline of only 11 million years between.. approximately 541

and 530 million years ago the original ancestors of almost all

the life forms we currently know today sprang into existence for example this is when fish first appeared

100

there was life before this event sure but this short window was

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when mother nature downed a red bull snorted some cocaine and hit the big evolutionary boost button

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so how does all this relate to the snowball earth theory well

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when all these ice flows started to hit the ocean they

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deposited gargantuan quantities of nutrient -rich minerals into the water where

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the theory goes it was responsible for the aforementioned explosion of

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life over 1 billion years of sedimentary rock was just carved

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from the face of the planet by glaciers then plunged into evolution's breeding ground,

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the ocean, where the many minerals contained within acted as a catalyst for life as we know it today.

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So, in the end, it looks like we did lose a billion years of history down the back of the sofa, only the sofa in question turns out to be the bottom of the ocean.

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But Snowball Earth remains a theory, one that was only posed as recently as 1998 by Dr Paul Hoffman, And, if you ask me,

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two decades doesn't seem like enough time to definitively explain a billion years of missing history.

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Maybe someday new techniques or technologies will rock the geology world

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and enable us to fill in more of the missing gaps in our planet's very long, very empty history book.

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But, until then, the great unconformity will remain a great mystery.

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Vocabulario y notas de pronunciación para esta lección

Esta lección de conversación de nivel C1 se basa en el vídeo “There's a Giant Hole In Earth's History”. Las palabras que más se repiten: rock, unconformity, billion, layer, gap. Este vídeo tiene 114 frases y 1597 palabras para practicar shadowing. La parte hablada dura 11:46. El hablante mantiene un ritmo constante de unas 136 palabras por minuto, cómodo para el shadowing. Solo el 76 % de las palabras está entre las 3.000 más comunes del inglés, por lo que el vocabulario es exigente.

Vocabulario clave de este vídeo

Las 15 palabras más avanzadas del vídeo, con su pronunciación y significado:

Palabra	Pronunciación	Significado
geologist sustantivo	/d͡ʒiˈɑːlədʒɪst/	geólogo, geóloga
sedimentary adjetivo	/ˌsɛd.əˈmɛn.tə.ɹi/	sedimentario
hiatus sustantivo	/haɪˈeɪtəs/	pausa, hiato
snowball sustantivo	/ˈsnoʊbɔl/	bola de nieve, bola nival
mineral sustantivo	/ˈmɪn.ə.ɹəl/	mineral
geologic adjetivo	/ˌd͡ʒi.əˈlɑdʒ.ɪk/	geológico
particle sustantivo	/ˈpɑɹtək(ə)l/	partícula
fossil sustantivo	/ˈfɑsl̩/	fósil
stratigraphy sustantivo	/stɹəˈtɪɡ.ɹəfi/	estratigrafía
stratum sustantivo	/ˈstɹeɪ.təm/	estrato
trifle sustantivo	/ˈtɹaɪfəl/	sopa inglesa
sandstone sustantivo	/ˈsændˌstoʊn/	arenisca
glacier sustantivo	/ˈɡleɪ.ʃɚ/	glaciar, helero
atop	/əˈtɒp/	encima de
erosion sustantivo	/ɪˈɹəʊʒən/	erosión

Phrasal verbs que vas a escuchar

Palabra	Significado
make over verbo	reformar

Gramática en este vídeo

Las estructuras que más usa el hablante, con las palabras exactas del vídeo:

Estructura	En el vídeo
Voz pasiva be + participio pasado — importa lo que ocurre, no quién lo hace	being littered · is formed · is frozen
Present perfect have/has + participio pasado — una acción pasada que sigue importando ahora	you've ever found · has come · it's been
Oraciones de relativo who / which + oración — información extra sobre una persona o cosa	Laurentia, which is · one that was

Pronunciación a tener en cuenta

El hablante usa 10 contracciones y formas reducidas, como you'd, you're, doesn't. Dilas en su forma corta, tal como las oyes.

Los sonidos de “sh” y “zh”: glacier /ˈɡleɪ.ʃɚ/, erosion /ɪˈɹəʊʒən/, enshrine /ɪnˈʃɹaɪn/, grayish /ˈɡɹeɪ.ɪʃ/, interruption /ˌɪntəˈɹʌpʃən/
Palabras largas — cuida el acento: geologist /d͡ʒiˈɑːlədʒɪst/, sedimentary /ˌsɛd.əˈmɛn.tə.ɹi/, geologic /ˌd͡ʒi.əˈlɑdʒ.ɪk/, stratigraphy /stɹəˈtɪɡ.ɹəfi/, accumulate /əˈkjuːmjʊˌleɪt/

Sonidos difíciles para hispanohablantes:

s + consonante al inicio — sin añadir una “e” delante: snowball /ˈsnoʊbɔl/, stratigraphy /stɹəˈtɪɡ.ɹəfi/, stratum /ˈstɹeɪ.təm/, span /spæn/, scuttle /ˈskʌt.l̩/
/v/ — no es /b/: los dientes tocan el labio inferior: definitively /dɪˈfɪnɪtɪvli/, dissolve /dɪˈzɑlv/, excavate /ˈɛk.skə.veɪt/, traverse /tɹəˈvɝs/, evolutionary /ˌiː.vəˈluː.ʃən.ɛɹ.i/
/z/ — sonora, no /s/: agonizingly /ˈæɡ.ə.naɪ.zɪŋ.li/, decompose /ˌdiːkəmˈpəʊz/, dissolve /dɪˈzɑlv/, superposition /ˌs(j)uː.pə(ɹ).pəˈzɪʃ.ən/, deposition /ˌdɛp.əˈzɪʃ.ən/

Cómo practicar con este vídeo

Escucha el vídeo entero una vez sin hablar y anota las palabras que no conoces.
Haz shadowing frase por frase a velocidad normal, repitiendo cada una hasta que tu ritmo coincida con el del hablante.
Grábate y compara con el original, prestando atención a palabras como geologist, sedimentary, hiatus.

¿Qué es la Técnica de Shadowing?

Shadowing es una técnica de aprendizaje de idiomas respaldada por la ciencia, desarrollada originalmente para la formación de intérpretes profesionales y popularizada por el políglota Dr. Alexander Arguelles. El método es simple pero poderoso: escuchas audio en inglés nativo y lo repites en voz alta de inmediato, como una sombra que sigue al hablante con solo 1-2 segundos de retraso. A diferencia de la escucha pasiva o los ejercicios de gramática, el shadowing obliga a tu cerebro y músculos de la boca a procesar y reproducir simultáneamente patrones de habla reales. Las investigaciones muestran que mejora significativamente la precisión de la pronunciación, la entonación, el ritmo, el habla conectada, la comprensión auditiva y la fluidez al hablar, convirtiéndola en una de las metodologías más efectivas para la preparación del IELTS Speaking y la comunicación en inglés en el mundo real.

Técnica de shadowing: lee la guía completa paso a paso →

Shadowing Practice: There's a Giant Hole In Earth's History - Learn English Speaking with Video

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