VOA慢速英语2021--冰川如何破裂并引发洪水

Indian rescuers searched on Monday for about 200 people missing after part of a Himalayan glacier¹ broke away Sunday and caused major flooding.

The flooding happened when part of the Nanda Devi glacier broke off, releasing water trapped behind it. The burst sent floodwater toward power plants and villages in northern Uttarakhand state. The floods destroyed bridges and broke dams. Huge amounts of water, rock and building materials flowed down a mountain valley.

At least 26 people are confirmed dead.

More than 2,000 military members, police officers and others have been taking part in search-and-rescue operations.

Most of the missing were people working on two hydroelectric power plants. The projects are part of government efforts to develop the mountainous areas of Uttarakhand state.

The floodwaters rushed down the mountain and into other bodies of water. Many villages along the Alaknanda and Dhauliganga rivers were evacuated³. The two rivers flow out of the Himalayan mountains and later join with the Ganges River.

Videos on social media show the muddy, gray floodwaters quickly flowing through a valley and into a dam, and breaking it into pieces before continuing downstream.

Experts said the disaster could be linked to climate change. A team of scientists was flown to the area Monday to investigate what happened.

How glaciers⁴ and glacial lakes are formed

A glacier is a very large area of ice that moves slowly down a mountainside or valley or over a wide area of land. Glaciers are made of closely formed layers of snow. They move or flow because of gravity and the softness of ice compared to rock.

A long and narrow piece of ice called a glacier's "tongue" can extend hundreds of kilometers from its beginnings in high mountains. The end of the tongue can advance or move backward based on snowfall and melting.

Bodies of water called proglacial lakes are formed after glaciers retreat, or move back. Extra water or pressure -- or structural⁵ weakness -- can cause both natural and manmade dams to burst. This sends a mass of floodwater flowing down the rivers fed by the glacier.

Why did this glacier burst?

It is not yet known what caused part of the Nanda Devi glacier to break off.

Seismic⁶ activity and a buildup of water pressure can cause glaciers to burst. But climate change may be another cause. High temperatures, combined with less snowfall, can increase the speed of melting. This causes water to rise to possibly dangerous levels.

Sarah Das is a scientist at Woods Hole Oceanographic Institute in Massachusetts. She told The Associated Press, "Most mountain glaciers around the world were much larger in the past and have been melting and shrinking dramatically due to climate change..."

Sunday's disaster happened in the western part of the Himalayas. The mountains form part of India's long northern border.

A 2010 information page published by the International Centre for Integrated⁷ Mountain Development called for more glacier observation in the Himalayas to better understand "the real degree of glacial lake instability."

The area where the glacial burst took place experiences landslides⁸ and flooding. Environmental experts have warned against building in the region.

Words in This Story

glacier - n. a very large area of ice that moves slowly down a slope or valley or over a wide area of land

hydroelectric - adj. of or relating to production of electricity by waterpower

rush - v. to move very quickly

evacuate² - v. to remove (someone) from a dangerous place

muddy - adj. filled or covered with mud (soft, wet dirt)

layer - n. a covering piece of material or a part that lies over or under another

advance - v. to move forward

seismic - adj. of, relating to, or caused by an earthquake

dramatically - adv. sudden and extreme

due to - adj. because of

instability - n. the state of being likely to change

region - n. a part of a country, of the world, etc., that is different or separate from other parts in some way

1 glacier   

n.冰川，冰河

参考例句：

• The glacier calved a large iceberg.冰河崩解而形成一个大冰山。
• The upper surface of glacier is riven by crevasses.冰川的上表面已裂成冰隙。

2 evacuate   

v.遣送；搬空；抽出；排泄；大(小)便

参考例句：

• We must evacuate those soldiers at once!我们必须立即撤出这些士兵！
• They were planning to evacuate the seventy American officials still in the country.他们正计划转移仍滞留在该国的70名美国官员。

3 evacuated   

撤退者的

参考例句：

• Police evacuated nearby buildings. 警方已将附近大楼的居民疏散。
• The fireman evacuated the guests from the burning hotel. 消防队员把客人们从燃烧着的旅馆中撤出来。

4 glaciers   

冰河，冰川( glacier的名词复数 )

参考例句：

• Glaciers gouged out valleys from the hills. 冰川把丘陵地带冲出一条条山谷。
• It has ice and snow glaciers, rainforests and beautiful mountains. 既有冰川，又有雨林和秀丽的山峰。 来自英语晨读30分（高一）

5 structural   

adj.构造的，组织的，建筑（用）的

参考例句：

• The storm caused no structural damage.风暴没有造成建筑结构方面的破坏。
• The North American continent is made up of three great structural entities.北美大陆是由三个构造单元组成的。

6 seismic   

a.地震的，地震强度的

参考例句：

• Earthquakes produce two types of seismic waves.地震产生两种地震波。
• The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。

7 integrated   

a.整合的，完整的

参考例句：

• A fully integrated low phase noise LC voltage controlled oscillator (VCO) is presented.介绍了一种全集成的LC压控振荡器(VCO)的设计。

8 landslides   

山崩( landslide的名词复数 )； （山坡、悬崖等的）崩塌； 滑坡； （竞选中）一方选票占压倒性多数

参考例句：

• Landslides have cut off many villages in remote areas. 滑坡使边远地区的许多村庄与外界隔绝。
• The storm caused landslides and flooding in Savona. 风暴致使萨沃纳发生塌方和洪灾。