分享成功
Listen to part of the lecture in the Astronomy class.
Um, many people have been fascinated about Venus for centuries because of its thick cloud cover, this so-called "planet of mystery and all of that".
Well what's under those clouds? What's the surface of the planet like?
Some questions about the surface are still unresolved, but we have learned a lot about it in past several years.
First of all, let me talk about how we've been able to get past those clouds.
First, there were Soviet modules that landed directly on the surface, and sent back some images of what was around them.
Second, we did some radar imaging from satellites from above.
Radar can get through the clouds.
So what have we learned?
Yes, Karen.
Well, I remember reading that there is not really a lot going on, that the surface of Venus is just flat and smooth in a lot of places.
Um, yeah, it's smooth in a lot of places but that's not, um, that's not the whole picture.
In other areas, you've got canyons, ripped valleys, meteor craters, uh, lava domes, these lava formations that look like giant pancakes, and also volcanoes.
Well, one of the most interesting features on the surface are in fact, the shield volcanoes.
Shield volcanoes formed when magma comes out of the ground, in the same spot over and over again.
Remember, magma is hot molten rock that's underground, and it's called lava when it reaches the surface.
Uh, so the lava builds up and hardens and a volcano forms.
Now the lava on Venus is thin, it spreads out easily.
So shield volcanoes have very gentle sloping sides.
They are called "shield volcanoes" because viewed from above, they kind of resemble shields, you know, like a warriors' shield.
But what's particularly interesting about these volcanoes is that most of the volcanoes here on Earth are not shield volcanoes.
nstead, they are other volcano types like strata volcanoes for example, which are the result of tectonic plate movement.
Remember tectonic plates?
Underneath the Earth's crust, there are a number of the shifting slabs or plates that are slowly moving.
草莓小菇凉:说的非常好，十分有道理，棒棒棒！
06-08 15:44:55