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Layers of the Earth

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Subido el 28 de mayo de 2007 por EducaMadrid

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NASA Sci Files segment exploring the many layers of the earth and how these relate to earthquakes.

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Hi, Dr. D. Hi, guys. What's up? 00:00:00
We felt our treehouse shake this morning and wanted to know what happened. 00:00:06
Yeah, I felt something, too. 00:00:09
We think that it might have been an earthquake, but we can't prove it yet. 00:00:11
Have you ever been in an earthquake? 00:00:15
Yes, I have, but it didn't feel the same as what I felt this morning. 00:00:17
See, I told you it wasn't an earthquake. 00:00:21
Wait a minute. All earthquakes don't feel the same. 00:00:24
To begin understanding earthquakes, you have to know something about the structure of the Earth. 00:00:26
That makes sense. What can you tell us? 00:00:31
Come on, let me show you. 00:00:33
Okay. 00:00:35
Let me cut this peach in half. 00:00:37
Okay, be careful. 00:00:39
I will, thanks. 00:00:40
This will be our Earth. 00:00:42
Only, it's a lot smaller. 00:00:44
It's called a scale model. 00:00:46
The pit is like the core of the Earth. 00:00:48
The Earth's core is about half of its diameter. 00:00:50
What's it made of? 00:00:52
We've never been there, but we think it's made of iron and nickel. 00:00:53
The inner part of the core is solid, and the outer part is liquid. 00:00:56
It is so dense, if we had a gallon jug full of the Earth's core material, it would weigh over 100 pounds. 00:01:00
Wait, Dr. D, you lost me. 00:01:06
How do we know how big the core is and what it's made of if we've never been there? 00:01:08
Well, it's just a guess. 00:01:12
You're kidding. 00:01:14
Well, actually, it's a pretty good guess, based upon a lot of evidence. 00:01:16
One of the biggest clues we have to the structure of the Earth comes from our study of earthquakes. 00:01:19
So we're using earthquakes to help us understand earthquakes? 00:01:24
That's right. 00:01:28
The part of the peach that you eat is called the Earth's mantle. 00:01:29
It's not as dense as the core, but it's more dense than what's on the outside. 00:01:32
What's the outside called? 00:01:36
It's called the crust. 00:01:38
Just like the crust of a bread. 00:01:39
Very good. 00:01:41
Like the skin of a peach, the Earth's crust is very thin. 00:01:42
The crust under the oceans is typically between 5 and 10 kilometers thick. 00:01:45
It's made of a dark, dense rock called basalt. 00:01:49
The continental crust is between 30 and 70 kilometers thick. 00:01:52
It's made of a lighter, less dense rock, like this granite. 00:01:56
Is there a reason why the Earth is layered like this? 00:01:59
It's because of density. 00:02:02
Watch us experiment over here. 00:02:04
I'm going to put this green-tinted water and this salad oil into this graduated cylinder and shake them up. 00:02:07
Let's see what happens. 00:02:17
The salad oil is on top, and then the water. 00:02:29
Let's put in some motor oil. 00:02:32
It turns out, the least dense, which is motor oil, floats on the top. 00:02:36
And the most dense, water, sinks to the bottom. 00:02:42
It's just like the early history of the Earth, when it was all liquid. 00:02:45
Earth, liquid, strange. 00:02:48
But what does this have to do with earthquakes? 00:02:51
When the Earth cooled, the crust's upper mantle became rigid and brittle. 00:02:53
They broke into about 12 segments, which we call plates. 00:02:57
These plates float on the more dense, but flexible, mantle below. 00:03:00
Kind of like this egg white. 00:03:04
These plates are in continual movement. 00:03:06
Wow, this is too weird. 00:03:08
Why don't we feel them moving? 00:03:10
They move about as fast as your fingernails grow, which is only a few centimeters per year. 00:03:12
But we have fossil evidence of this movement, which we call plate tectonics. 00:03:16
Are fossils also clues to understanding earthquakes? 00:03:20
Yes. 00:03:23
But Dr. D, aren't there other things that could cause vibrations? 00:03:25
Well, yes, that's a good question. 00:03:28
Anything that makes a very loud sound can make things shake a little. 00:03:30
I watched fireworks on the 4th, and some were so big, I did feel a vibration. 00:03:33
Oh no, I'm late for an appointment. 00:03:38
Why don't you take a little and discuss this amongst yourselves? 00:03:40
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Idioma/s:
en
Niveles educativos:
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Autor/es:
NASA LaRC Office of Education
Subido por:
EducaMadrid
Licencia:
Reconocimiento - No comercial - Sin obra derivada
Visualizaciones:
251
Fecha:
28 de mayo de 2007 - 15:33
Visibilidad:
Público
Enlace Relacionado:
NASAs center for distance learning
Duración:
03′ 50″
Relación de aspecto:
4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
Resolución:
480x360 píxeles
Tamaño:
23.19 MBytes

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