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Listen to an Academic Talk Test #049
Listen to an Academic Talk
1. What is the main purpose of the lecture?
A) To compare different types of volcanoes
B) To explain a cause of volcanic activity
C) To describe the geography of the Hawaiian Islands
D) To discuss the theory of tectonic plates
2. According to the professor, what is a key feature of a geological hotspot?
A) It moves along with the tectonic plate.
B) It creates earthquakes but not volcanoes.
C) It is found only at plate boundaries.
D) It remains in a fixed location.
3. What would a geologist likely conclude about an island in the Hawaiian chain?
A) The islands in the northwest are the youngest.
B) A new island will probably form to the southeast.
C) The entire chain of islands formed at one time.
D) The movement of the Pacific Plate has stopped.
4. Why does the professor mention the Hawaiian Islands?
A) To illustrate the effects of a hotspot
B) To show a place where tectonic plates meet
C) To question a long-held geological theory
D) To describe the most dangerous type of volcano
Professor: So, we know that most earthquakes and volcanoes occur where tectonic plates meet. But what about volcanoes that pop up in the middle of a plate, far from any boundary? The Hawaiian Islands are a perfect example. These were formed by what we call hotspot volcanism.
A hotspot is a fixed point deep in the Earth's mantle where a plume of extremely hot material rises and melts the rocky crust above it, creating a volcano. The crucial point is that the hotspot itself is stationary, but the tectonic plate above it is constantly moving.
So, as the Pacific Plate has drifted slowly to the northwest, it has passed over the Hawaiian hotspot. This process formed a chain of volcanic islands. The oldest, inactive islands are in the northwest, while the youngest and most active island, Hawaii itself, is currently right over the hotspot. This gives geologists a fantastic tool for tracking plate movement over millions of years.
A hotspot is a fixed point deep in the Earth's mantle where a plume of extremely hot material rises and melts the rocky crust above it, creating a volcano. The crucial point is that the hotspot itself is stationary, but the tectonic plate above it is constantly moving.
So, as the Pacific Plate has drifted slowly to the northwest, it has passed over the Hawaiian hotspot. This process formed a chain of volcanic islands. The oldest, inactive islands are in the northwest, while the youngest and most active island, Hawaii itself, is currently right over the hotspot. This gives geologists a fantastic tool for tracking plate movement over millions of years.
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