Science column: The largest moving thing on earth
THE LARGEEST MOVING THING ON EARTH
Published: Monday, September 30, 2013
Updated: Monday, September 30, 2013 21:09
We’ve all heard of global warming, right? It’s a complex issue. No one is sure what’s causing it, how we stop it, if we need to stop it or exactly what will happen if we don’t. However, one of the scariest potential side effects of a warmer climate is sea level rise. If global warming continues, the sea level could potentially rise more than 60 meters!
Think about that, folks. People like to live near water — many of our biggest cities are on the coast, and if the sea rose up 60 meters, a lot of us would need to start taking scuba tanks to work.
Why, though? Why does a warmer climate mean more sea water? It’s because ice would melt. A lot of ice. Up to 10 percent of the world’s land surface is currently covered with giant, frozen, moving rivers of ice. That’s right: glaciers.
Glaciers are large, solid, land-based bodies of compacted ice and snow. They form over thousands of years and play a large part in our planet’s temperature and stability. Also, they’re really, really cool.
Glaciers hold 75 percent of the world’s freshwater. Currently they cover 10 percent of the world’s land surface, but, for example, during the last ice age, they covered 32 percent. Every time the planet gets colder, glaciers grow, and every time it gets warmer, they shrink. If all of the glaciers melted, that would cause the 60-meter sea level increase. To be fair, it’s not likely that all of them would melt quickly enough for New York City to end up underwater in a matter of months, but it is possible.
Glaciers are the largest moving things on Earth. The largest one in North America is the Bering Glacier in Alaska, and it is 127 miles long. Glaciers “flow” just like rivers of liquid water. They crack, shift and deform under their own weight. Any small amount of melting leads to imperfections, faults and cracks, and under the influence of gravity and its own immense weight, glaciers are all slowly “flowing” downhill.
The fastest glacier movement ever recorded happened in Pakistan in 1953. The Kutiah Glacier moved more than 7.5 miles in just three months — it could be observed moving about 350 feet per day.
Glaciers have played a large role in shaping our planet and our lifestyle. When a glacier “flows” over an area it scrapes out the rock and dirt under it, leaving behind a large trough. This is called glacial erosion. Additionally, when a glacier melts and “retreats” or shrinks, it leaves behind sediments that it has picked up over the years. Glaciers formed many of the structures seen in the United States today, when they were more prominent in the many ice ages.
They also have a large impact on our planet’s albedo. Albedo is the reflectivity of the Earth’s surface. White, shiny surfaces like snow and ice reflect more sunlight than dark surfaces like plants and soil. Thus, when more of the Earth is covered in snow and ice, Earth has a higher albedo. When the albedo is high, more sunlight is reflected off of Earth and back into space, and less of it stays in our atmosphere. This means a higher albedo — and less solar energy — actually leads to cooler temperatures, and a lower albedo leads to warmer temperatures. Some aspects of global warming may be self-fulfilling like this one. As the glaciers melt, the albedo drops, and more and more solar energy is absorbed into our system, leading to higher temperatures and more melting.
Glaciers are also a good natural resource. Places like Bolivia and Peru, with their high elevation, and Canada and Alaska, because of their northern location, tap into glaciers for drinking water and crop irrigation. Many private companies tap glaciers in the Antarctic.
In addition, by storing all of the fresh water they do, glaciers are keeping our sea level low and our oceans salty. If they were to all melt tomorrow, many sea-dwelling creatures would die because of the addition of cold, fresh water to our oceans, and many of our cities would be flooded and ruined.
Glaciers can also be dangerous. They can cause avalanches and flooding when they melt rapidly. In addition, they are the source of icebergs, a danger for ships of all kinds. When a large chunk of a glacier breaks off of the main body, it splashes into the sea and floats around on its own — it’s now an iceberg. Icebergs are dangerous because they float very low in the water; what you can see above the surface is just the very tip, and they can be wide and sharp underneath the ocean.
When icebergs break off glaciers, it is called “calving.” You can hear the creaking, groaning sound from miles away, and it is truly an example of the raw power of nature in action and also what inspired me to write this post in the first place.
To see a video of a glacier calving, and to learn more, visit www.dinnertablescience.com.