Glacier vs Iceberg

Diffen › Science › Geology

Icebergs and glaciers are both enormous masses of snow, built up over the years through natural processes. However, they are both different from each other in form and structure, as well process of formation. Glaciers are formed by continual deposition of snow at a place where it does not melt. When a chunk of this glacier breaks off and floats in the water, it is known as an iceberg.

Comparison chart

Glacier versus Iceberg comparison chart
	Glacier	Iceberg
Formation	Incessant deposition of snow and other frozen precipitation. Glaciers grow partly by spreading due to their weight.	Broken off of a glacier. When a chunk of glacier breaks off it is called calving
Size	Larger	Smaller
Location	Mountains, valleys and polar regions	Fresh or sea water beds
Exposure	Entirely above water level	10% above water level
Introduction	A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years, often centuries.	Ice bergs are formed from breaking off glaciers.
Terminology	When a chunk of glacier breaks off it is called calving	A fresh iceberg is also called a calf.
Composition	Pure snow and ice on a bed of "fluid ice" (the pressure of the ice above is higher than the skew strength of the ice at the bottom).	Pure ice floating on fresh or salt water. The portion of the iceberg above water is higher in sea water.
Debris	As a glacier grows, it pushes objects ahead and to the side of it. This is called Moraine.	In some cases, a glacier digs canyons (called fjords, pronounced like fyords). These are left over after most of the glacier has calved.

Seals basking in the sun on an iceberg

How are glaciers and icebergs formed?

Glaciers are formed with incessant deposition of snow, which transforms into ice, over time. As time passes, the ice crystallizes into sugar-like granules and compresses the air pockets that are present. With time, the crystals become larger in size and the air pockets become of negligible size. This process consumes almost a hundred years.

When a chunk of this glacier breaks off, an iceberg is formed.

This video gives an overview of what qualifies as a glacier and how glaciers are formed:

Differences in Size

A glacier is far larger in size than an iceberg because glaciers are formed by continual deposition of snow, over as many as hundred years. Some of them are so massive that if they melt, they would cause sea-levels to rise. Icebergs are comparatively smaller because they are nothing but pieces that are broken off from glaciers, which then float on water.

Image Gallery

An iceberg in the North Atlantic Ocean

Perito Moreno Glacier	A beautiful iceberg in Antarctica	An ice climber navigating delicate terrain - Cerro Torre Glacier in Argentina
Rafters approaching an iceberg cave in North East Greenland

Location

Glaciers are generally formed atop mountain valleys (valley glaciers) or in Polar Regions (continental glaciers), where the snow that falls never melts away.

Icebergs, when they break off from glaciers, generally float on water bodies. They might come to a standstill in a shallow bed of water, which is called an ice scour and the structure the iceberg transforms into is known as an ice island. Therefore it might float in the form of an ice shelf, which is constantly on the move or become stable like pack ice.

Exposure

A glacier is situated on land and therefore is entirely exposed. On the other hand, all we can see of an iceberg is its tip. Because the iceberg floats on water, more than 90% of it is actually submerged.

Why do Icebergs Float?

Icebergs are made of pure ice, the density of which is 920 kg/m3. The density of water is 1025 kg/m3. Icebergs float because they are lighter than water. What we actually see is only the tip of the iceberg, the major portion of the structure lies right beneath.

Variants

There are several types of iceberg, which are classified according to their shapes and sizes. According to their shapes, icebergs are classified into tabular (plateau shaped) and non-tabular. Non-tabular iceberg shapes include the Dome (rounded shape), Pinnacle (with spires), Wedge (steep edge on one side and smoothly sloped on the other), Blocky (steep vertical sides and a flat top) and the Dry Dock (one which has developed channels or tunnels due to erosion).

The following video provides an overview of what icebergs are, how they form, how they get their color and size, and their role in the environment.

Such detailed classifications of glaciers are not prevalent. At best, they are broadly classified based on the location where they were formed liked valley glaciers and continental glaciers.