1.Listen to part of the lecture in the Astronomy class.

1.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".

2.Well what's under those clouds? What's the surface of the planet like?

3.Some questions about the surface are still unresolved, but we have learned a lot about it in past several years.

1.First of all, let me talk about how we've been able to get pasted those clouds.

2.First, there were Soviet modules that landed directly on the surface, and sent back some images of what was around them.

3.Second, we did some radar imaging from satellites from above.

4.Radar can get through the clouds.

5.So what have we learned?

6.Yes, Karen.

1.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.

1.Um, yeah, it's smooth in a lot of places but that's not, um, that's not the whole picture.

2.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.

3.Well, one of the most interesting features on the surface are in fact, the shield volcanoes.

1.Shield volcanoes formed when magma comes out of the ground, in the same spot over and over again.

2.Remember, magma is hot molten rock that's underground, and it's called lava when it reaches the surface.

3.Uh, so the lava builds up and hardens and a volcano forms.

1.Now the lava on Venus is thin, it spreads out easily.

2.So shield volcanoes have very gentle sloping sides.

3.They are called "shield volcanoes" because viewed from above, they kind of resemble shields, you know, like a warriors' shield.

1.But what's particularly interesting about these volcanoes is that most of the volcanoes here on Earth are not shield volcanoes.

2.Instead, they are other volcano types like strata volcanoes for example, which are the result of tectonic plate movement.

1.Remember tectonic plates?

2.Underneath the Earth's crust, there are a number of the shifting slabs or plates that are slowly moving.

3.And in the zones on the edges of the plates where different plates meet and interact, that's what we get most of the Earth's volcanoes.

1.On Venus, however, volcanoes are not clustered in discrete zones like they are on the Earth.

2.Instead, they are more or less randomly scattered over the Venus' surface.

3.Well, that's significant.

4.Venus has mostly shield volcanoes, and they are randomly scattered that indicates that Venus doesn't have moving tectonic plates, and that's a big difference compared to the Earth.

5.Here on Earth, moving tectonic plates are a major geological elements,just crucial for the whole surface dynamics, right?

1.So why doesn't the Venus have them?

2.Well, there are a few theories.

3.Um, one of them is that this has to do with the fact that Venus has no surface water that's needed to kind of lubricate the movement of the plates, you know, like oceans on Earth.

4.Yeah, I forgot to spell that out, Venus has no surface water.

1.Wait a second.

2.Did you say we have the shield volcanoes on Earth? Can you give us an example?

1.Sure, the volcanos on the Hawaii islands in the Pacific Ocean are the shield volcanoes.

2.They are formed over a hot spot magma.

3.So while on Earth's we have several types of volcanoes, on Venus, there is mostly the one type.

1.Uh, Eric?

2.Are the volcanoes on the Venus still active?

1.Well, that's an interesting question.

2.There is still some discussion on that point, but here is what we do now.

3.First, the level of sulfur dioxide gas above Venus's clouds shows large and very frequent fluctuations.

4.It's quite possible that these fluctuations, the huge increase and decrease of sulfur dioxide happening again and again.

5.It's quite possible that this is due to volcanic eruptions, because volcanic eruptions often emit gases.

6.If that's the case, volcanism could very well be the root cause of Venus's thick cloud cover.

7.And also we have observed bursts of radio energy from the planet's surface.

8.These bursts are similar to what we see when volcanos erupt on the Earth.

9.So this two suggests ongoing volcanic activity.

10.But although this is an intriguing evidence, no one has actually observed a Venus' volcano erupting yet, so we can't be positive.