1 . The Best Caves in The World
Hang Son Doong, Vietnam
Natural caves don’t come much larger than Hang Son Doong, close to the border between Laos and Vietnam. This cave possesses the largest cross-section of any known cave on the planet, a vast area that is difficult to describe. Supposedly, a Boeing 747 could fly through without damaging its wings, but that doesn’t really do justice to the vastness of Hang Son Doong. The stalactites (钟乳石) here are pretty massive too, with some reaching up to 80 metres.
Waitomo Caves, New Zealand
Glowworms (萤火虫) are there, as far as the eye can see. Okay, not literally, but the Waitomo Cave system on New Zealand’s North Island is best-known for the fluorescent fauna that light up the walls, giving it the not-particularly-creative but completely acceptable “Glowworm Caves” nickname. They are more accessible than other caves on this list, with rafting and adventure tours available to those looking for something a little more thrilling.
Mammoth Cave, the USA
If you have certain expectations from somewhere called “Mammoth Cave”, that is entirely understandable. Mammoth Cave in Kentucky is the world’s longest known cave system, an incredible 420 miles of underground wonder. That’s twice as long as the next longest, by the way, although it isn’t unusual for the USA to go all out on such things.
Reed Flute (芦笛) Cave, China
Named after the reeds that grow outside, which are used to make flutes, obviously, the Reed Flute Cave’s walls are covered with inscriptions from centuries gone by—if evidence was needed that people have been paying attention to this place for a long old time. The inside part of the cave is also lit up by multicoloured lights, giving it a real otherworldly theme that adds weight to the nickname.
1. What is special about Hang Son Doong?| A．It was once a base of a factory. |
| B．It is the deepest cave in the world. |
| C．It has the highest stalactites in the world. |
| D．It owns the largest cross-section in the world. |
| A．Hang Son Doong. | B．Waitomo Caves. |
| C．Mammoth Cave. | D．Reed Flute Cave. |
| A．Vietnam. | B．New Zealand. | C．The USA. | D．China. |
2 . In the 1960s, while studying the volcanic history of Yellowstone National Park, Bob Christian-sen became puzzled about something that, strangely, had not troubled anyone before he couldn’t find the park’s volcano. It had been known for a long time that Yellowstone was volcanic in nature—that is what accounted for all its hot springs and other steamy features. But Christian-sen couldn’t find the Yellowstone volcano anywhere.
Most of us, when we talk about volcanoes, think of the classic cone(圆锥体)shapes of a Fuji or Kilimanjaro, which were created when erupting magma(岩浆)piled up. These can form remarkably quickly. One day in 1943, a Mexican farmer was surprised to see smoke rising from a small part of his land. In one week he was the confused owner of a cone five hundred feet high. Within two years it had topped out at almost fourteen hundred feet and was more than half a mile-across. Altogether there are some ten thousand of these volcanoes on Earth, all but a few hundred of them extinct. There is, however, a second less known type of volcano that doesn’t involve mountain building. These are volcanoes so explosive that they burst open in a single big crack, leaving behind a vast hole, the caldera(火山口).Yellowstone obviously was of this second type, but Christian-sen couldn’t find the caldera anywhere.
Just at this time NASA decided to test some new high-altitude cameras by taking photographs of Yellowstone. A thoughtful official passed on some of the copies to the park authorities on the assumption that they might make a nice blow-up(放大的照片)for one of the visitors’ centers. As soon as Christian-sen saw the photos, he realized why he had failed to spot the caldera: almost the whole park—2.2 million acres -was a caldera. The explosion had left a hole more than forty miles across-much too huge to be seen from anywhere at ground level. At some time in the past Yellowstone must have blown up with violence far beyond the scale of anything known to humans.
1. What does the underlined word “its” in paragraph 1 refer to?| A．The ground. | B．The nature. |
| C．The volcano. | D．The park. |
| A．A single big crack was forming there. | B．Someone was burning stalks there. |
| C．A volcano was erupting underneath. | D．There were some hot springs there. |
| A．By looking at the photographs. | B．By analyzing its steamy features. |
| C．By researching historical documents. | D．By using some advanced equipment. |
| A．Its level is much higher than the surrounding areas. |
| B．The volcano in it involved mountain building. |
| C．It is a large hole left by the explosion. |
| D．Its shape is much like a cone. |
