토플독해(Delta's Toefl Reading Sections)

Questions 7-10

 

A hot spot is a giant underground caldron of molten rock in one of the world's many volcanically active areas. The steamy geysers, thermal pools, and mud pots of Yellowstone National Park owe their origins to hot spots.

 

Annually, more than 200 geysers erupt in Yellowstone, making this one of the most interesting places in the world for geologists. Over 100 geysers lie within the Upper Geyser Basin, a one-square-mile area near Old Faithful, the most famous geyser in the world. The Yellowstone hot spot was created around ten million years ago, and the center of the park is still volcanically active, with molten rock only a mile or two beneath the Earth's surface.

 

When rain and melted snow seep down through tiny cracks in the Earth, the water eventually reaches underground chambers of lava-heated rock. The rock heats the water, and the boiling water and steam often make their way back up to the surface in the form of a geyser, a thermal pool, or a mud pot.

 

In a geyser, water trapped in an underground chamber heats up beyond the boiling point and forms steam. Since steam takes up 1,500 times more space than water, pressure builds up, eventually forcing the superheated water to burst to the surface as a geyser. A thermal pool is formed when the water from the hot spot reaches the surface before cooling off. If the water does not make it all the way to the surface, steam and gases may dissolve rocks and form a bubbling mud pot instead. (260 words)

 

______ min. ______ sec.

 

7. Where do hot spots occur?

 

Ⓐ In rocky regions near the equator

Ⓑ Below the ground near active volcanoes

Ⓒ About a mile above a volcano's crater

Ⓓ In the center of ancient volcanoes

 

8. According to the passage, why is Yellowstone National Park an interesting place for geologists?

 

Ⓐ There are 100 square miles of hot spots.

Ⓑ Over 200 geysers miles of hot spots.

Ⓒ There are more than 100 different kinds of geysers.

Ⓓ More than 200 types of rock are found there.

 

9. How do hot spots contribute to the formation of geysers?

 

Ⓐ Hot spots melt all of the snow falling into a volcano's crater.

Ⓑ Water is trapped in an underground chamber and cannot escape.

Ⓒ Hot rocks create boiling water, steam, and pressure underground.

Ⓓ Water from hot spots rises to the surface before it cools off.

 

10. When do mud pots form?

 

Ⓐ When steam and gases dissolve rocks near the surface

Ⓑ When underground water exceeds the boiling point

Ⓒ When snow melts in Yellowstone's geyser basins Ⓓ When superheated water bursts to the surface