CNN 2010-04-09（在线收听）

CARL AZUZ, CNN STUDENT NEWS ANCHOR: Hi, I'm Carl Azuz. You're tuned in to CNN Student News. Afghanistan, Iraq, D.C.: lot of ground to cover today. We start things off in West Virginia.

First Up: Coal Mine Disaster

AZUZ: Officials there are trying to figure out what caused the worst U.S. mining disaster in 25 years. It happened Monday afternoon at the Upper Big Branch South Mine: a massive blast inside the coal mine that killed at least 25 people, left four others trapped. Rescue workers are trying to drill their way into the mine, but they need to get 1,200 feet down inside of it, and that could take a while. Not only is the process slow, it's dangerous. Crews are having to deal with potentially harmful gases.

President Obama and other officials, including both of West Virginia's U.S. senators, have offered their thoughts and prayers to the families of the miners. They've also said they're determined to find out what happened and how it can be prevented in the future. One government official said, "Miners should never have to sacrifice their lives for their livelihood." This all happened inside a facility that does what's called longwall mining. Tom Foreman explains how that works and its potential dangers.

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TOM FOREMAN, CNN CORRESPONDENT: This is a type of mining that was actually pioneered in England several hundred years ago, but has really caught on in the past 30 years here because of new technology, primarily because mine owners have believed that this new technology might allow them to automate further, which would reduce the risk to miners and produce more coal.

So, let's check a little section of the land here. If we were to cut part of this out just like that, and we were able to move this aside, and say this is what it looks like underneath. This is from YouTube; a fellow put together a demonstration with what happens with longwall mining.

You may notice here -- this is a seam of coal -- and you'll see there had been little rooms cut in on the sides over here. This is the beginning of longwall mining. You cut off an area like this. You create a field, and this may be enormous. It's like 800 feet across here. It can be as much as a mile or more, along this way. And then, this is what happens: They start cutting away at the face of that. It's about eight feet tall. They cut, cut, cut, cut, cut. You can see a tremendous amount of coal would come out of it cutting it this way.

But I do want to point out that this video is a little bit deceptive, because what you don't see here is as they're cutting all that coal out, you're not creating a big giant room here. What you're doing is you're allowing it to all collapse in behind you as you cut. So, you're actually filling in all of this area with the mountainside collapsing behind you. And the actual working area is actually only about 15 feet or so from the face right up in here. So, this is the area we're looking at when we're focusing on this idea of longwall mining.

You have all of this space here. That grinding on the surface up front produces an enormous amount of coal dust. That's what you're seeing right there and that's the issue of ventilation here. What are the dangers if you have this kind of operation going on on the face of coal? You have this issue of coal dust building up. That's a potential threat because it is enormously explosive. You also have the threat of methane building up if it's not vented enough, also enormously explosive. And because of all the weight here and the width of this, you always have the danger of some kind of structural collapse.

Again, many people believe this is less likely to produce a structural collapse than the other method of cutting out little rooms and leaving pillars, but nonetheless, when you put all these together, this is the danger.