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Faults
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NASA Sci Files segment exploring faults and how they contribute to eartquakes.
Ready, R.J.?
00:00:00
Hey, guys. I'm here at the San Andreas Fault,
00:00:04
near where the epicenter of the 1906 San Francisco earthquake occurred.
00:00:08
Hi, guys. You must be the treehouse detectives. How can I help you?
00:00:12
Our friends in Virginia felt a vibration the other day,
00:00:15
and they wanted to find out if it was an earthquake.
00:00:18
They said we needed to learn more about faults.
00:00:20
Well, a fault is a weak zone in the Earth's crust
00:00:22
where the rock layers have broken and slipped apart.
00:00:24
Would you like to see the San Andreas Fault?
00:00:27
R.J., be sure and get me on camera.
00:00:29
Okay.
00:00:31
So where's the fault line?
00:00:38
You can see it here.
00:00:40
See the line that goes up the wall?
00:00:42
Are there different kinds of faults?
00:00:47
Yes, there's three kinds of faults.
00:00:49
One is called a normal fault, and that's when the fault is at an angle,
00:00:51
and the top block is called the hanging wall,
00:00:54
and that moves down relative to the lower block called the foot wall.
00:00:57
And this happens where there's extension in the crust and it pulls apart.
00:01:00
Is there an abnormal fault?
00:01:03
Well, it's not really an abnormal fault,
00:01:05
but there is a fault that's opposite of a normal fault,
00:01:07
and that's when the hanging wall block moves up relative to the foot wall block.
00:01:09
And this happens where there's crustal compression,
00:01:13
and those faults are called reverse faults or thrust faults.
00:01:16
What's the last type of fault?
00:01:19
Well, the last kind of fault is called a strike-slip fault,
00:01:20
and that's like where we are now on the San Andreas Fault.
00:01:22
We learned that the Earth's lithosphere is broken up into plates,
00:01:25
and the plates' movement is what causes earthquakes.
00:01:28
But I don't get it. Are plates and faults the same thing?
00:01:30
Well, moving plates grind and scrape against each other at their edges,
00:01:33
and those edges we call plate boundaries,
00:01:37
and plate boundaries are usually made up of many faults.
00:01:39
Are there different kinds of plate boundaries like there are different kinds of faults?
00:01:42
Yes, there's also three of those.
00:01:46
Divergent boundaries are where the crust is being pulled apart.
00:01:48
These can form new crusts or cause rift valleys and even make volcanoes.
00:01:51
The pulling apart can happen at about two centimeters a year.
00:01:55
That's not very much. It must move really slowly.
00:01:58
Yeah, they do.
00:02:01
And a convergent boundary is where the plates crash head-on.
00:02:02
Oh, those boundaries move slowly too.
00:02:05
Yeah, they do. They only move a few centimeters a year,
00:02:07
and because it's slow, it can take millions of years for them to form.
00:02:10
And when the plates collide, sometimes you can get large mountain chains like the Himalayas.
00:02:13
Wow, now I'm starting to understand why the Earth is shaped the way it is.
00:02:18
The last boundary is called a transform boundary.
00:02:22
It's when plates slide past each other, like the San Andreas Fault here.
00:02:24
Does that mean California is not going to break off and fall into the ocean?
00:02:28
No, that's a common misconception.
00:02:31
Actually, Los Angeles may someday be next to San Francisco,
00:02:33
but that will probably take 10 million years.
00:02:36
That's a long time.
00:02:38
I don't think we have any boundaries in Virginia.
00:02:40
Do earthquakes occur anywhere else?
00:02:42
Yeah, a few earthquakes occur in the middle of plates, called interplate earthquakes.
00:02:44
And in 1886, there was a large earthquake in Charleston, South Carolina.
00:02:48
South Carolina is near Virginia.
00:02:52
Maybe they did have an earthquake.
00:02:54
Do you want to try making your own earthquake?
00:02:56
Will it knock houses down?
00:02:58
No, it won't be a real earthquake. It'll just be a simulation of a very small one.
00:02:59
Let's go.
00:03:03
I have a setup here that we're going to pretend is like the Earth's plates moving.
00:03:04
So you're going to turn the crank and apply stress to these blocks.
00:03:08
You're going to cause a force to be pulling them,
00:03:11
and this is going to be the equivalent of one plate,
00:03:13
and this is going to be the equivalent of another crustal plate.
00:03:15
And watch as you add more and more stress and see if you can get an earthquake.
00:03:18
RJ?
00:03:23
Wow, was that an earthquake?
00:03:29
Yeah.
00:03:31
Now that's my kind of earthquake.
00:03:32
This has really been helpful. Thank you.
00:03:34
Sure. Well, email me if you have any more questions.
00:03:36
Okay.
00:03:39
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- Idioma/s:
- Niveles educativos:
- ▼ Mostrar / ocultar niveles
- Nivel Intermedio
- Autor/es:
- NASA LaRC Office of Education
- Subido por:
- EducaMadrid
- Licencia:
- Reconocimiento - No comercial - Sin obra derivada
- Visualizaciones:
- 219
- Fecha:
- 28 de mayo de 2007 - 15:33
- Visibilidad:
- Público
- Enlace Relacionado:
- NASAs center for distance learning
- Duración:
- 03′ 40″
- 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:
- 22.10 MBytes
