Preparation for the Toefl listening section with examples and exercises. Please use the subtitles at first as this will help you improve your vocabulary and general understanding. As you progress you will be able to understand without the subtitles.
Lesson 19 Dialogue
Based on what you hear in the toefl listening section, you should be able to decide what logically might happen next, or be able to reason what the speaker means – what is implied – by saying or asking something. For this type of question, it’s the opinions, feelings, thoughts of the speaker you need to be able to understand and not just the factual information. It’s a difficult type, but it’s also not used very often.
Example: Transcript of the passage you would HEAR:
Narrator: Listen to part of a lecture in an Earth science class.
Professor: Can any of you tell me exactly what a geyser is? If you can’t, don’t worry – geysers are a relatively overlooked phenomenon – in my opinion, anyway… especially compared to geological wonders like volcanoes or glaciers.
In simple terms, a geyser is an opening in the earth’s surface that erupts intermittently, releasing groundwater that’s been what we call geothermally heated. It’s very possible that geysers are low-profile because there are so few of them in the world to study – less than 700 worldwide – and they all exist in about a dozen concentrated groups. There are so few of them because special chemical and geological conditions must exist for a geyser to form.
First off… underground, there’s got to be a series of channels or chambers in the shape of a “tube,” or “neck,” pointing upward, towards the earth’s surface. Geologists have created 6 major geyser models, varying significantly in shape. Some of them look similar to… tree roots, with long necks and a series of water caverns at their bases. Others look more similar to a series of “lungs” with a channel in the center and caverns of water connecting to this channel. However, nearly all of them are similar in that they have relatively wide cavernous areas deep underground, where water can gather. Then, as the neck of the geyser nears the surface, it constricts. A geyser [emphasis] must have this constriction to form; it is the choke point which forces the superheated water of a geyser into an observable fountain.
Secondly… the groundwater I mentioned seeps into these channels, which are pretty deep – deep as in hundreds of feet below the surface. There, the water [emphasis] must come into direct contact with, or at least within close range of magma. You remember what magma is, right? Molten… extremely hot… liquid rock found beneath the earth’s surface. So… once the groundwater fills the geyser’s channels, which have been left empty by the last eruption, it is superheated by the magma.
Then, steam bubbles form in the upper region of the geyser channel, where the boiling point of the water is lower because there’s lower pressure. A chain reaction then occurs: water at the top boils off, allowing water beneath it to rise. This water itself boils off and it in turn is replaced by water beneath it. Water then at lower and lower levels rises and boils off. Eventually, the water near the very bottom of the channel also boils, resulting in a mixture of water and steam finally erupting through the geyser’s surface vent. The entire process can be likened to a pressure cooker with a very small hole in the top lid. Once the entire pot of water comes to a boil, water shoots up and out through the hole.
Now, the water you see venting from the geyser is usually centuries old: scientists estimate that it takes a minimum of 500 years for water to seep down deep enough to become heated by magma.
But none of this would be possible without the third necessary condition to form a geyser… and this is where a little bit of chemistry comes in: the groundwater must also interact with rock that contains silica – or the dioxide form of silicon. Why? Well, silica is soluble in hot water, and as it dissolves its chemistry changes. As the groundwater containing the silica rises toward the Earth’s surface, some of the chemically altered silica is deposited on the inner walls of the channels, forming a… coating called sinter… also known as geyserite. This coating smoothes the high-pressure release of water and steam upward through the channels… forcefully… to the Earth’s surface. The sinter is what turns the rocky channel into a “pipe” that reaches from deep within the earth up to the surface. If it weren’t for the sinter, the pressure would be released through cracks and holes in the walls of the geyser channels.
There’s no real consistency to when geysers erupt – some do so regularly… others are more unpredictable. Some eject only minor amounts of water and steam a few feet in the air; others for hundreds of feet! Remember how I said that many geysers are found in clusters? Well, over 60% of the world’s geysers are right here in the U.S. – in Yellowstone Park, which of course is home to possibly the most famous geyser of them all, Old Faithful.
Question for the toefl listening section: What does the professor imply about geysers?
A. They are an untapped source of geothermal energy.
B. Large ones tend to erupt less predictably than small ones.
C. They deserve more attention than they receive.
D. They are similar to volcanoes in some ways.
Explanation: (C) is the correct answer. At the start of her lecture, the professor says she believes that geysers are “… a relatively overlooked phenomenon… especially when compared to geological wonders like volcanoes or glaciers.” Lots of people know about volcanoes and glaciers, but not many know about geysers. She explains why geysers aren’t well known, but it’s also clear from her entire lecture that geysers are very interesting and deserve to be known better than they are. Choice (A) is incorrect. The professor only mentions that when geysers erupt, they release groundwater that’s been geothermally heated. She never suggests that geysers could be an energy source. Choice (B) is incorrect. The size of a geyser being a factor of how frequently they erupt is not talked about. The professor does say, “There’s no real consistency to when geysers erupt – some do so regularly… others are more unpredictable.” Choice (D) is not mentioned.
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