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Listen to an Academic Talk Test #064
Listen to an Academic Talk
1. What is the professor's main purpose?
A) To explain how fossils are formed
B) To describe a specific geological process
C) To discuss the composition of volcanic ash
D) To compare different types of rocks
2. What condition is necessary for petrification to begin?
A) The wood must be exposed to oxygen
B) The tree must be very old when it dies
C) The wood must be buried by sediment
D) The temperature must remain very high
3. What can be inferred from the talk?
A) Petrified wood is not a common type of fossil
B) The petrification process happens relatively quickly
C) Petrified wood contains no original organic material
D) Scientists can learn about ancient trees from petrified wood
4. Why does the professor mention seeing the cellular structure under a microscope?
A) To emphasize the accuracy of the mineral replacement
B) To explain how difficult it is to study petrified wood
C) To suggest that all petrified wood looks the same
D) To describe a common classroom activity
Professor: Today I want to talk about how wood can turn into rock. This amazing natural process is called petrification, and it results in what we know as petrified wood. It's essentially a type of fossil. This happens when a tree is buried under sediment, like volcanic ash or mud, shortly after it dies. This burial is crucial because it protects the wood from decay due to oxygen and organisms. Over millions of years, water rich in dissolved minerals, especially silica, seeps through the sediment and into the wood. As the original wood cells slowly rot away, these minerals are deposited in their place, creating a perfect stone replica of the original wood. Sometimes the replication is so precise that you can see the tree's original cellular structure under a microscope. This gives us a detailed record of ancient forests.
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