Most people think of a large mass of snow moving down a mountain when they hear the word “glacier.” The kind that you see in thriller films – an irregularly shaped, cloud-like bulky structure of snow rolling downhill while the actor who happens to be in its path tries skiing away hurriedly to avoid being crushed under it.
But glaciers are a lot more enthralling than that. As much as they elicit awe, glaciers make one curious about what these dense snow formations really are.
Glaciers have long been the point of interest for scientists and geologists. A lot of in-depth research has been done on glacial landforms that include studies on how they are formed, the way in which they affect the surrounding areas and the world’s oceans at large.
Just like rivers carve out valleys and alter the nearby landscape, glaciers also sculpt mountains, form crevasses and shape the landscape as they flow. Some glaciers are only found on mountains whereas others end in the sea when chunks of glacier ice break off in a process called calving and float atop the water surface.
Glaciers are an important indicator of climate change or to be more specific, global warming. Various glaciers around the world also attract tourists and inspire adrenaline-driven adventure seekers to come and observe these gigantic wonders from up-close.
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[Source: Geology]
Read on to learn more about these magnificent ice masses. The article discusses the different types of glaciers plus some interesting facts about glaciers that will blow your mind (or rather freeze it).
What Is a Glacier?
Before moving on to the different types of glaciers, it’s essential to understand what a glacier really is. An excessively large amount of snow accumulated on a mountain or any other piece of land is not necessarily a glacier.
A glacier is defined as a slowly moving mass of ice formed on mountains or near the poles. It is made up of thousands of tons of snow fallen over many years.
When a large amount of fallen snow remains in one location for a significantly long period of time, it becomes compressed and compacted under its own weight. This leads to the creation of huge, thickened masses of ice known as glaciers. Glaciers are also called ‘rivers of ice’ because despite being solid ice, they are in constant motion.
[Source: Alaska Satellite Facility]
How Are Glaciers Formed?
The primary requirement for the formation of glacial ice is the accumulation of a considerably large amount of snow. If more snow falls during the winter season than the amount that melts away in summer, snow starts to accumulate.
Within two years, the soft and once delicate snowflakes turn into hard crystalline or granular snow called firn. As more and more snow gets layered on top with the passage of time, the pressure melts the grains just a tiny bit. However, they quickly recrystallize and this forms what is known as glacier ice.
The natural phenomenon of glacier formation can take several decades or even hundreds of years to complete.
[Source: National Geographic]
Click here to read our article about other natural phenomena that can be seen around the world!
Types of Glaciers
In the broader sense, glaciers can be generally classified into two main groups: unconstrained glaciers and constrained glaciers. Since glacier morphology is affected by the temperature, precipitation and the natural landscape where they form, they can vary greatly in size and shape.
The term glacier can include massive continental ice sheets, small cirques located on mountain tops and anything in between.
Unconstrained Glaciers
As the name suggests, these types of glaciers are rather freely forming ice masses that are not affected by the surrounding landscape. The natural topography or the underlying bedrock does not hinder the accumulation and movement of snow for the formation of these glaciers.
Unconstrained glaciers include ice sheets and ice caps as well as ice streams and ice domes.
Constrained Glaciers
Constrained glaciers form between mountain peaks, valleys and the likes. The shape, structure, and size of constrained glaciers are influenced by the surrounding landforms because the ice flow is ‘constrained’ by the bedrock.
Types of constrained glaciers include valley glaciers, cirque glaciers, and piedmont glaciers to name a few.
Continental Glaciers
Continental glaciers, also known as ice caps or continental ice sheets, are the largest glaciers on the planet. About 99% of the glacial ice on earth is contained within ice sheets. The Antarctic ice sheet and Greenland ice caps alone cover more than 50,000 square kilometers.
These glaciers are not bounded by mountains or similar landform. Thus, they tend to spread out in all directions and cover everything in their path. When ice sheets fan out from the center, entire valleys, plains, and even mountains ranges get perched in snow.
At times, as more and more ice gathers, ice sheets can extend over the sea as well. They tend to float in the sea and are known as ice shelves. You might have heard about these glaciers or seen them on TV as more and more news circulates about the alarmingly rapid rate at which they are melting.
What makes continental perhaps the most important type of glacier is the fact that this glacial ice not just serves as a reserve of fresh water but it feeds most of the other glacier types. For example, the Harding Icefield feeds about 40 different glaciers in Alaska.
Mountain Glaciers
As is evident by the name, these glaciers are formed in the mountainous regions. Depending on the geographical location, shape and similar factors, different glaciers can be classified as a mountain glacier.
However, the size of the ice mass is one thing that is generally not considered when defining a mountain glacier. A mountain glacier might span over a single mountain, stretch out over several peaks or even extend over the entire mountain range.
The distinct feature of mountain glaciers is the fact that these glaciers are surrounded by mountainous terrain on all sides. The may be found on the sides of the mountain but they end on the slope only which means that they don’t flow into the main river.
If a mountain glacier increases in size and approaches or ends in a valley, then the whole ice mass is referred to as a valley glacier. The largest mountain glaciers in the world are located in Alaska and Arctic Canada. Other regions include the Himalayas in Asia and the Andes in South America.
