【正文】 alachian Mountain Range is, of course, thousands of kilometers to the east of the Grand Canyon. Sounds pretty unbelievable, right? Of course, the obvious question is how did that sand end up so far west? The theory is that huge rivers and wind carried the sand west where it mixed in with the sand that was already there. Well, this was a pretty revolutionary finding. Um… and it was basically because of Uranium Lead Dating. Why? Well, as everyone in this class should know, we usually look at the grain type within sandstone, meaning the actual particles in the sandstone, to determine where it came from. You can do other things too, like look at the wind or water that brought the grains to their location and figure out which way it was flowing. But that‘s only useful up to a point, and that‘s not what these two geologists did. UraniumLead Dating allowed them to go about it in an entirely different way. What they did was: they looked at the grains of Zircon in the sandstone. Zircon is a material that contains radioactive Uranium, which makes it very useful for dating purposes. Zircon starts off as molten magma, the hot larva from volcanoes. This magma then crystallizes. And when Zircon crystallizes, the Uranium inside it begins to change into Lead. So if you measure the amount of Lead in the Zircon grain, you can figure out when the grain was formed. After that, you can determine the age of Zircon from different mountain ranges. Once you do that, you can pare the age of the Zircon in the sandstone in your sample to the age of the Zircon in the mountains. If the age of the Zircon matches the age of one of the mountain ranges, then it means the sandstone actually used to be part of that particular mountain range. Is everybody with me on that? Good. So, in this case, UraniumLead Dating was used to establish that half of the sandstone in the samples was formed at the same time the granite in the Appalachian Mountains was formed. So because of this, this new way of doing UraniumLead Dating, we‘ve been able to determine that one of our major 托福聽力文本 詞匯注解（ TPO1TPO26） 張志軍 北京 7 assumptions about the Grand Canyon was wrong. Like I said before, UraniumLead Dating has been with us for a while. But, um… until recently, in order to do it, you really had to study many individual grains. And it took a long time before you got results. It just wasn39。reini?m] n. 鈾 [39。ve been talking about in class. Student Oh! OK, yeah, so like when he was teaching them astronomy, he didn39。ve been pretty cold during the winters. And it also looks like they made their tools near the fire. There tends to be a lot of obsidian flakes and chips in the hearth ashes, but no chimney. The smoke just went out the same hatchway that people used for going in and out themselves. So there would have been an open fire inside the house with only one hole in the roof to let the smoke out. You and I would have found it a bit too smoky in there. You can see on the walls, which they plastered and decorated with paintings. They ended up with a layer of black soot on them, and so did people‘s lungs. The bones found in the graves show a layer of soot on the inside of the ribs. And that‘s another unusual feature of Catalhoyuk, the burial sites. The graves have all been found under the houses, right under the floors. And it maybe this burial custom that explains why the houses were packed in so tightly without streets. I mean, you might think it was for protection or something, but there has been no evidence found yet of any violent attack that would indicate that kind of danger. It maybe they wanted to live as near as possible to their ancestors‘ graves and be buried near them themselves. But it makes a good point. Based on excavations, we can know the layout of the houses and the location of the graves, but we‘re only guessing when we tried to say why they did it that way. That‘s 托福聽力文本 詞匯注解（ TPO1TPO26） 張志軍 北京 11 the way it is with archaeology. You are dealing with the physical remains that people left behind. We have no sure access to what they thought and how they felt about things. I mean it‘s interesting to speculate. And the physical artifacts can give us clues, but there is a lot we can‘t really know. So, for instance, their art. They painted on the plastered walls and usually they painted hunting scenes with wild animals in them. Now they did hunt and they also raised cereal crops and kept sheep, but we don‘t know why so many of the paintings are of hunting scenes. Was it supposed to have religious or magical significance? That‘s the kind of thing we can only guess at based on hopefully, further excavation of Catalhoyuk will yield more clues. But we‘ll probably never know for sure. [?ɑ:ki39。?gjul?] , 長(zhǎng)方形的 , 直角的 [39。s not about the time it takes for Eastern marmots to grow. It‘s when the food is available. That is when it‘s not covered in snow and there is no frost covering the grass and, umm, vegetative parts of a plant‘s herbs and the flowers the marmots like to eat. So growing season refers to the availability of the food they eat, OK? So now how would you describe the Eastern marmots‘ social habits? Student Well, they are really territorial, and loners, and just so aggressive even with other Eastern marmots. And their mating ritual is just so impersonal. Professor Uhha? Now when they emerge in the spring from hibernation, the mating process begins. For them, well, they e together to mate and then they go their separate ways. Then about six to eight weeks after birth, the offspring leave their mothers. Student Really? Just six weeks? Is that possible for the offspring to make it on their own so young? Professor Well, it‘s not as if they aren39。t have to rely on each other too much and they really don39。t?wei] n. 艙口 , 地窯口 , 天窗