A glacier essentially forms after several years of snow have packed down and hardened. The heavy ice begins following gravity down a slope, causing it to flow very much like a river. These powerful streams of ice can shape whole mountain ranges, scooping out canyons and valleys in their wake. Today I will share some interesting tidbits about glaciers.
Those you see on the mountains did not come from the Ice Ages.
Though some of the glaciers near the poles may be older, most mountain glaciers did not grow during the Ice Age. All those glaciers melted during warm periods following the beginning of the Holocene. The mountain glaciers you see today are all around 700 years old or less, most of them forming during the Little Ice Age, a slight cooling period from the 1400s to the 1800s. Some glaciers, such as the one that has formed in the crater of Mount Saint Helens, are even younger. This particular glacier is less than 40 years old.
They can tell us about the planet’s past.
This is especially true of the polar ice caps, where the ice is older than those on mountains discussed above. Paleoclimatologists can determine variations in Earth’s climate through the sampling of ice cores. These cores contain bubbles of greenhouse and other atmospheric gases that can tell scientists what the composition of the atmosphere was at the time the ice was formed. These cores also contain pollen, dust, trace elements, and even volcanic ash and sulfur, all of which can provide valuable information on what was going on during that time period.
They are threatened by black carbon.
Black carbon is soot and other particulate pollution that is created primarily by the combustion of fossil fuels and biofuels. This carbon has a short life in the atmosphere before dropping onto snow and glaciers, especially in the Arctic and the Himalayas. The deposits absorb heat and warm up the snow and ice, causing it to melt at more rapid rates. This, along with climate change, is threatening the existence of Earth’s glaciers today.
They provide much of the planet’s freshwater supply.
According to the United States Geological Survey, up to 2.1% of the Earth’s water is contained within glaciers. Most water is found in the oceans and under the planet’s surface. However, glaciers contain three quarters of the Earth’s freshwater supply, making the world’s glaciers the biggest freshwater reservoir on the planet.
Antarctica’s ice is not being melted by volcanoes.
Some people claim that the rapid melting of Antarctica’s ice pack is due to subglacial volcanoes. However, recent studies have contradicted this hypothesis. Though volcanic eruptions under the ice have caused small collapses and water ponding, these volcanoes are not having a major impact on the ice sheet. Most of the thinning and recession that has been observed is on the coast, where the ice is influenced by warmer ocean temperatures. It’s climate change, not volcanoes.
Mount Rainier’s glaciers eat airplanes.
Though this is probably true for glaciers on many mountains, it is most noticeable on Mount Rainier because of the dense ice pack. There are two known plane crashes to have occurred on the mountain in the twentieth century, including a military transport in 1946 that left several people permanently entombed on the South Tahoma Glacier. A small plane that disappeared in 1972 was found within the Cowlitz Glacier twenty years later, where the ice had melted back during a drought period. No one knows exactly how many planes are under the massive ice cap at this huge volcano, but no doubt there are more out there somewhere.
They have the power to polish rocks.
Glaciers have scouring power similar to sandpaper, which allows them to polish down rocks they are passing over and leave them with a shiny surface. They also tend to leave grooves known as striations. Geologists can use this polish and these striations to figure out what direction a glacier flowed during the Ice Age.
Their floods are known as jokulhlaups.
This is an Icelandic word that originally referred to volcano-related glacial floods, but now refers to many different forms of glacial outbursts. These bursts are so powerful and contain so much water that they sometimes exceed the water flow of the Amazon Basin. The floods are caused by the rapid melting of ice, such as might occur with geothermal heating or a volcanic eruption, or just a changing climate. They were very common during the end of the Ice Ages, when glaciers receded and melted rapidly, causing massive, record-breaking floods.
There are rock glaciers.
These are essentially glaciers that contain a large cover of rock and talus on top. They are common in mountainous terrain, where they frequently resemble landslides. However, there is ice actively flowing underneath the rocky mantle. No one actually knows what that ice looks like because the rock layer is so thick, so there is no way of telling whether the rocks are throughout the glacier or just sit on top. This is a geologic mystery yet to be solved.
They can change Earth’s climate.
The thermohaline cycle is basically a set of deep ocean currents that are caused by changing densities and temperatures of ocean water. Denser, saltier, colder water sinks below the surface while lighter, warmer water rises. This serves as a heat regulator for the planet. However, when large amounts of glacial meltwater from the polar ice caps enters the ocean, it can cause this cycle to stall and the planet suffers a cooling period. Some climatologists believe this is partially what caused the Little Ice Age, which followed a warm period very similar to what we are seeing today.
When I was a kid I was not a fan of glaciers. I thought they were just boring piles of ice and snow that carved scars into my favorite Earth features, volcanoes. This was, of course, before I got to take a walk on the top of the Columbia Ice Field in Canada and saw where all the water that flowed down the Columbia River actually came from. No, glaciers still aren’t my favorite geological feature (volcanoes will always win that contest), but they are far more fascinating than I used to think.
United States Geological Survey- www.usgs.gov
Climate & Clean Air Coalition- www.ceacoalition.org
National Park Service- www.nps.gov