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Speaking. Chapter 3. Focus B 1.

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√ 01 Geography
√ 02 Geology




01 Geography





M: Good day, everyone. Today, we’re going to be looking at some

    of the effects the moon has on our lives. Can anyone tell me
    one such effect?
W1: Well, ummm, I’ve heard that full moons make people do crazy
    things.
M: Ha ha. Yes, I’ve heard that, too. Some statistics support that idea,
    but other studies refute it. In any case, you can debate that more
    in your psychology classes. But this is geography, so what physical
    effect does the moon have on our planet?
W1: Oh, OK then. Well, how about the tides? The moon’s gravitational pull causes the tides, right?
M: Right you are. That’s the information I was looking for, thank you.
    So, we know the moon causes tidal movement in the oceans, but
    can the moon cause rain? Do the moon and sun create tidal effects
    in the atmosphere as well as the oceans? In the past century, an
    air tide, or rather a kind of shifting of the atmosphere has been
   recognized. That, specifically, is what we’re going to discuss today.
    As always, you are more than welcome to ask any questions you
    have as we go along.
    The possibility of gravitational tides in the Earth’s atmosphere
    was first suggested by Sir Isaac Newton. Newton is most famous
    for what discovery? Anyone?
W2: Wasn’t he the gravity guy?
M: The gravity guy? Yes, I think you could say that. Newton was
    the first person to describe the force of gravity. Now, he came
    up with this theory on atmospheric tides while developing an
    explanation for ocean tides. Since 1918, scientists have been
    measuring air tides in the Northern Hemisphere, and although the
    changes in air pressure are small, their effects are not. Studies have
    shown that more cloudiness, rainfall, and storms are generated
    during certain lunar phases, such as the full moon.
    In fact, even before Newton set down his theories on tides, people
    were aware that lunar phases corresponded with the rise and
    fall of the ocean tides. More recently, we have found that the moon
    is even able to cause deformations in the solid crust of the Earth.
    So, much in the same way the moon affects tidal movement in
    certain ways, it also pulls on the Earth’s crust as well, causing it to
    move, too. Yes. Amazing, isn’t it? The ground we walk on every day
    isn’t necessarily as solid as it seems! Yes, there in the blue sweater?
W1: The textbook mentions that the moon can cause an atmospheric
    tide, and that it can create changes in air pressure. Is this an air
    tide, and is it true that these changes in air pressure can cause
    hurricanes?
M: Ah, as I was saying earlier, studies have shown an increase in
    storms corresponding to certain lunar phases. While we cannot
    yet explain this in full, it does appear that the moon has an
    influence on the weather. Whether they directly cause hurricanes
    or not, well, we’ll have to wait for further research to determine
    that with any certainty, I’m afraid.
    Let’s look more at what happens during a full moon, though.
    Researchers at the University of Arizona discovered that at the
    time of a full moon, the temperature of the lower four miles of
    the Earth’s atmosphere increases by a few hundredths of a degree.
    Now, a few hundredths of a degree may not sound like much to
    you, and you probably couldn’t feel the difference yourselves, but
    it is significant. These researchers suggest that the moon warms
    our atmosphere in two ways. First, the moon’s surface is heated
     by the sun and radiates thermal energy at the Earth. This energy
     is much less intense than the energy we get directly from the sun,
     but it is supplemented by a second phenomenon. The moon of
     course mirrors, or reflects, sunlight at the dark, or night, side of
     the Earth. However, the mirror effect is relatively slight because it
     reflects just 10 percent of the light of the sun. Nonetheless, as you
     all have experienced, I’m sure, that 10 percent is quite significant
     when compared to the zero percent reflected during a new moon.
T   he difference is night and day, so to speak, if you’ll forgive the
     pun. Anyhow, what I want you to take away from today’s lecture
    is the fact that the moon can affect our weather. While we still have
    much to learn, we may well be justified in blaming the moon for
    a rainy day!



02 Geology.





W: Today, I’ll begin with the basics about minerals. It’s important

    that you supplement this information by reading chapter 3 in
    your textbook because I’m sticking only to the bare bones here.
    All right...it’s essential to remember that both chemical composition
    and crystal structure together define a mineral. Some students
    find that surprising. They think that crystals are pure --- are just one
    element. That may be true for some crystals, but not all. Minerals
    range in composition from pure elements and simple salts to very
    complex silicates with thousands of known forms. So to define
    a mineral, we have to figure its composition. What all is in it?
    Now, here is a useful tip that may save you a point or two on the
    next exam. Organic compounds are usually excluded from the
    category mineral. Got that? If it’s organic, don’t classify it as a
    mineral. In fact, there are five main criteria for calling something a
    mineral. Let’s go through those criteria. First of all, it must be in a
    solid state, not liquid, gas, or plasma. Minerals are solid. Second, it
    must be naturally occurring. In other words, it can’t be man-made.
    Third, it has to be inorganic. Like I said, if it’s organic, it’s not a
    mineral. So, third --- oh, sorry --- we’re on number four now. Fourth,
    for something to be a mineral, it needs to have a fixed composition,
    which means the chemical composition is the same everywhere it
    is found and every time it is found. Mineral X found in my backyard
    is going to have the same composition as Mineral X found in
    Australia. Finally, our fifth criterion is that a mineral must be
    either an element or a compound; so it cannot be a mixture of
    a chemical compound and an element. Don’t worry if that last
    one seems a bit vague at the moment. We’ll talk a lot more
    about that over the next couple of classes.
    Sometimes we get certain cases that satisfy all but one criterion.
    That’s close, but not a mineral. These things are usually classified as
    mineraloids. Pearls would be a good example. Pearls are solid. They
    occur naturally. They have a fixed composition, and they’re a
    compound. The only criterion they don’t meet is the “inorganic
    test.” Pearls are actually a mixture of organic and inorganic
    substances. So, because they have that extra organic stuff mixed
    in, we can’t classify them as minerals. Pearls should be called
    mineraloids.
    Now, here’s another interesting case. Two or more minerals may
    have the same chemical composition, but differ in crystal structure.
    These are known as polymorphs. A good example of a polymorph
    pair is pyrite and marcasite, which are both iron sulfide. Let’s create
    a simple analogy to help you grasp that concept in case you’re
    confused. Let’s say Michelangelo has one large piece of marble.
    He splits it in two. One piece, he carves into the shape of a horse,
    and the other piece into the shape of a woman. They are exactly
    the same in chemical composition, but nobody would really claim
    they’re the same after he’s finished. Think of pyrite and marcasite
    as two of nature’s sculptures, both made of iron sulfide!
     All right, let’s see if you’ve been listening (laughs). Here’s my
    question. How about frozen H2O...or ice in layman’s terms? Is
    it a mineral? Anybody? Yes, Sam?

M: Well, I’m not positive about this, but...in liquid state, it’s just a
   chemical compound, right? But as ice it becomes a mineral.
W: We’ve got the five criteria for minerals, right? Tell me about each
    one in terms of ice and we can check.
M: OK. Ice is a solid with crystalline structure, and it’s not a humanmade
    substance. Ice isn’t alive and never has been; it’s...how did
    you put it?...exactly the same everywhere you find it and every time
    you find it, or whatever; it’s a pure compound although it might
    have other elements suspended in it. Did I cover everything?
W: Well done, Sam. I’m glad somebody was listening (laughs). You’re
    absolutely right. Ice is a mineral.
M: Kind of strange though. Before this class, I never would have
    thought of ice as a mineral.
W: I agree that it’s odd to think of it as a mineral. That’s because
    most of the minerals around us seem like metals or rocks. Most
    people forget that minerals come in many states of matter and
    forms. That’s why we have those five criteria for determining
    whether or not a substance is a mineral. Also, we need to keep
    in mind that both chemical composition and crystal structure
     together define a mineral.

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