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Listen to an Academic Talk Test #009
Listen to an Academic Talk
1. What is the main topic of the lecture?
A) The differences between the three main rock types
B) The process of tectonic plate movement
C) The commercial uses of marble and slate
D) The formation process of metamorphic rocks
2. According to the professor, how does limestone become marble?
A) By being melted and then cooling slowly
B) By being eroded by wind and water
C) By being subjected to heat and pressure
D) By mixing with volcanic ash
3. What can be inferred about an area where a large amount of slate is found?
A) It was once covered by an ocean.
B) It has experienced very little geological change.
C) It was likely the site of a volcano.
D) It has been exposed to significant geological forces.
4. Why does the professor define the word "protolith"?
A) To introduce the starting material for a metamorphic rock
B) To contrast it with the final rock product
C) To highlight a term students often misuse
D) To give an example of an igneous rock
Professor: We've talked about igneous and sedimentary rocks. Today, we'll cover the third main type: metamorphic rocks. The word 'metamorphic' means 'to change form,' and that's exactly what these rocks do. They start out as some other type of rock—the original rock is called a protolith—which can be igneous or sedimentary.
This protolith is then subjected to intense heat and pressure, usually deep within the Earth's crust, often due to the movement of tectonic plates. This process changes the rock's mineral composition and texture without melting it.
A great example is the transformation of limestone into marble. Limestone is a sedimentary rock, but under high heat and pressure, its crystals realign and grow, forming the much harder rock we know as marble. Similarly, the rock shale transforms into slate. Studying these rocks helps geologists understand the powerful forces that have shaped our planet's history.
This protolith is then subjected to intense heat and pressure, usually deep within the Earth's crust, often due to the movement of tectonic plates. This process changes the rock's mineral composition and texture without melting it.
A great example is the transformation of limestone into marble. Limestone is a sedimentary rock, but under high heat and pressure, its crystals realign and grow, forming the much harder rock we know as marble. Similarly, the rock shale transforms into slate. Studying these rocks helps geologists understand the powerful forces that have shaped our planet's history.
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