Why does glaciers cause floods?

Answer 1

A glacier is nothing more than a frozen river still moving. It might only move an inch or two per year, but it still moves and this ice will erode the ground and rock below it faster and more agressively than if it was just water. Its because glaciers also pick up and move the rocks that they run over and this gravel (chunks of rocks) can carve mountains down and cut valleys miles deep.Glaciers are huge chunks of snow and ice most time more than 1000 feet thick. They weigh huge amount and overtime become so condensed that they are harder than the rock they are on top of. They move at slow rates and the ice and erodes the rock into a fine powder that is then left behind. They erode the rock over hundreds of years and create huge valleys.The emerald lakes that form at the snouts of glaciers are a beautiful sight, but rapidly melting glaciers can cause these lakes to breach their walls, inundating villages downstream. To reduce the threat, the Worldwide Fund for Nature (WWF) and the United Nations Environmental Program (UNEP) monitor and drain some of these lakes.Melting of glaciers is perfectly normal. The only criterion is that falling snow must exceed the melting ice to sustain the glacier. Many people worldwide depend on melting glaciers for survival. All their freshwater needs are met by these melting glaciers year through. This is the water these people use for drinking and irrigation. If this source of fresh water were to stop it will create chaos. People will be forced to shift to places with other sources of freshwater. Certain nations depend a lot on the flow of this water for the production of electricity.

The overflow of water from melted ice into rivers can also cause flooding around the rivers. Villages that are set up around rivers could be destroyed when river banks burst. For example, according to a reporting by Newsweek, an increased rate of melting at the Colonia Glacier caused the flooding of Baker River in Chilean Patagonia in 2009, destroying roads, bridges and farms around the river.

One of the most obvious and well-known outcome of rapid glaciers melting is rising sea levels. The Inter-Governmental Panel on Climate Change (IPCC) has projected major changes in sea-level over the next 100 years if carbon dioxide levels continue to rise at the current rate. According to NASA, the average global sea level over the last century has risen by about 4 to 8 inches -- this means about 3.27mm per year. The rising sea level will cause flooding along coastal areas. Some cities and islands that are low lying can even get totally submerged.

Corals require sunlight for photosynthesis to survive and thrive but as the sea level rises from glaciers melting, insufficient sunlight reaches these corals. This will lead to the coral's deterioration (such as coral reef bleaching) and eventual death. Many marine species that depend on the corals for food will also die, or even become extinct. Read about endangered marine animals.

While melting glaciers are caused by global warming, glaciers melting can also impact the temperatures across the globe. Glaciers deflect almost 80% of the heat from the sun back into space. With the melting of ice glaciers, the earth below becomes exposed. There is less reflection of the sun's ray back into space and the glaciers absorb more heat, resulting in further increase in the global temperatures. A vicious cycle is created.

Almost 70% of our earth's surface is covered with water but most of this water is salt water. Freshwater makes up only about 2% of the water on this earth. A large proportion of the world's population depends on melting water from glaciers into lakes and rivers for freshwater supply. With glaciers melting at faster rate than what the rivers can normally hold, the fresh drinking water overflows into the sea and is wasted. The decreased mass of the shrinking glacier also spells water supply shortages in the near future. In fact, people living in the places near Himalayas are already facing water shortages.

Melting glaciers also affect the farmlands that depend highly on water emanating from ice glaciers. There will be a shortage of fresh water to these farms due to receding glaciers. Lack of availability of fresh water for irrigation will in turn reduce the farms' total agricultural output, spelling food shortages in those areas.

There are many animals, birds and fish that highly depend on glaciers for their survival. Animals like polar bears lose their habitats as the glaciers melt away. As some parts of the ice-land become ice-less and streams previously formed from melting ice dries out, the bears also loose their fishing grounds. Some of them starve to death.

Hydroelectricity plants depend solely on the constant flow of water for electricity generation. With melting glaciers, the long term flow of water through hydroelectricity plants located in the glacier regions would be reduced, reducing the efficiency of these plants to generate electricity. Lack of hydro electricity will put pressure on other sources, such as burning of fossil fuel, to produce electricity.

Ice weighs about one ton per cubic meter and glaciers are massive sheets of ice. The substantial weight of glaciers exerts enormous pressure on the earth, suppressing earthquakes. According to NASA, when this pressure is reduced as a result of glaciers melting, many geologic reactions like earthquakes, volcanic eruptions and tsunamis (caused by undersea earthquakes) can be triggered. This is because the tectonic plates are now free to move against one another, and the friction that results in the abrasion between plates can lead to earthquakes.