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An exceptional natural phenomenon occurred in Alaska last summer, serving as a powerful reminder of the increasing hazards posed by melting glaciers in the region. Scientists have now confirmed that a colossal wave, known as a ‘megatsunami’, was generated when a significant portion of an Alaskan mountain collapsed into the sea. This event has been identified as the second tallest megatsunami ever recorded globally.

The giant wave surged through a secluded fjord in southeast Alaska. Despite causing considerable destruction, the incident received minimal public attention at the time. However, a recent scientific analysis has brought to light the extraordinary magnitude of the event. An estimated 64 million cubic metres of rock, a volume comparable to 24 Great Pyramids, plummeted into the water in under a minute. The immense force of this landslide produced a massive wave almost 500 metres in height. Researchers highlighted that it was only due to the event occurring in the early hours of the morning that numerous tourist cruise ships, typically present in the area, were spared from the devastation.

Dr. Bretwood Higman, a geologist from Alaska who witnessed the aftermath at Tracy Arm Fjord, described it as a “close call”. He voiced significant apprehension, stating his fear that humanity “will not be so lucky in the future.”

Megatsunamis are enormous waves that arise when a substantial landslide, triggered by an earthquake or unstable rock, plunges into a body of water. Unlike open-ocean tsunamis, which are caused by underwater earthquakes or powerful volcanic eruptions and can travel thousands of miles, megatsunamis are typically localised, confining their impact to a smaller area and tending to dissipate rapidly. The largest recorded megatsunami in history, exceeding 500 metres, took place in the 1950s.

Alaska is particularly susceptible to these occurrences due to its distinct geographical features, combining steep mountains, narrow fjords, and frequent seismic activity. New research published in the journal Science indicates that the ongoing retreat of glaciers, driven by climate change, is making such geological collapses even more probable and severe. Dr. Stephen Hicks of University College London clarified that glaciers traditionally provide structural support to these rock formations. As the ice recedes, it exposes the base of cliff faces, rendering them unstable and thereby enabling these destructive landslides to occur.

1. What is the main purpose of the article?

• A.To warn tourists about the dangers of cruise ship travel in Alaska.
• B.To describe a recent megatsunami in Alaska and discuss the escalating risk of similar future events.
• C.To compare the Alaskan megatsunami with the 2011 Japan tsunami and other historical events.
• D.To explain the scientific difference between megatsunamis and open-ocean tsunamis.

2. What was the estimated height of the megatsunami wave that occurred in Alaska?

• A.Over 500 metres.
• B.Around 64 million cubic metres.
• C.Nearly 500 metres.
• D.Comparable to 24 Great Pyramids.

3. What did Dr. Bretwood Higman mean by calling the event a ‘close call’?

• A.It was fortunate that no tourist ships were present when the wave struck.
• B.The event happened very near his observation point, causing personal danger.
• C.The megatsunami was nearly as large as the record-breaking one from the 1950s.
• D.He almost missed witnessing the aftermath of the devastation.

4. According to the article, why is Alaska particularly vulnerable to megatsunamis?

• A.It has a large population living in coastal areas prone to tsunamis.
• B.Its remote fjords and mountains are rarely monitored by scientists.
• C.The region experiences frequent volcanic eruptions and underwater earthquakes.
• D.It combines steep mountains, narrow fjords, and regular seismic activity.

5. The word ‘dissipate’ in paragraph 4 is closest in meaning to

• A.intensify
• B.fade away
• C.spread out
• D.become destructive