As soon as Christiansen saw the photos, he realized why he had failed to spot the caldera.

2019年高考英语江苏卷 阅读理解 阅读B 原文

But Christiansen couldn't find the Yellowstone volcano anywhere.

2019年高考英语江苏卷 阅读理解 阅读B 原文

In the 1960s,while studying the volcanic history of Yellowstone national park,bob christiansen became puzzled about something that,oddly,had not troubled anyone before：he couldn't find the park's volcano.

2019年高考英语江苏卷 阅读理解 阅读B 原文

Yellowstone obviously was of this second type, but Christiansen couldn't find the caldera anywhere.

2019年高考英语江苏卷 阅读理解 阅读B 原文