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Listen to an Academic Talk Test #010
Listen to an Academic Talk
1. What is the lecture mainly about?
A) The chemical composition of water
B) The formation of mountain ranges
C) A specific type of rock erosion
D) The effects of climate on road quality
2. According to the speaker, by how much does water expand when it freezes?
A) Around nine percent
B) Almost nineteen percent
C) Less than one percent
D) About ninety percent
3. In which environment would frost wedging be most effective?
A) A hot desert with very little rainfall
B) A tropical rainforest with constant high temperatures
C) A polar region where ice never melts
D) A mountain area with temperatures that cross freezing daily
4. What is the purpose of mentioning potholes?
A) To suggest a research topic for students
B) To provide a familiar example of a geological process
C) To criticize the methods used for road construction
D) To explain why road maintenance is expensive
Professor: Today we'll look at a surprisingly powerful force of mechanical weathering known as frost wedging.
This process happens when water gets into cracks and fissures in rocks.
When the temperature drops below freezing, that water turns to ice.
Now, the key fact here is that when water freezes, it expands by about nine percent.
This expansion exerts an enormous amount of pressure on the surrounding rock, widening the crack.
Then, when the ice thaws, water can seep even deeper into the newly widened crack.
This cycle of freezing and thawing, repeated over and over, can eventually split huge boulders apart.
You see this on a smaller scale with potholes on roads.
Over geological time, this simple process is a major factor in breaking down mountain ranges and creating the landscapes we see today.
This process happens when water gets into cracks and fissures in rocks.
When the temperature drops below freezing, that water turns to ice.
Now, the key fact here is that when water freezes, it expands by about nine percent.
This expansion exerts an enormous amount of pressure on the surrounding rock, widening the crack.
Then, when the ice thaws, water can seep even deeper into the newly widened crack.
This cycle of freezing and thawing, repeated over and over, can eventually split huge boulders apart.
You see this on a smaller scale with potholes on roads.
Over geological time, this simple process is a major factor in breaking down mountain ranges and creating the landscapes we see today.
Highlights
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