A glacier is a large, perennial accumulation of crystalline ice, snow, rock, sediment, and often liquid water that originates on land and moves down slope under the influence of its own weight and gravity.

Here are 18 interesting facts about glaciers.

1.
Glaciers are huge masses of ice that "flow" like very slow rivers. They form over hundreds of years where fallen snow compresses and turns into ice.

2.
Glaciers are usually divided into two groups – Alpine glaciers, which form on mountainsides and move downward through valleys, and Continental ice sheets, which spread out and cover larger areas.

3.
Today, glaciers cover around 10% of the Earth's total land area. During the last ice age they covered 32%.

4.
Because glacial ice is so dense and compact, it often appears a bright blue colour!

5.
Glaciers form the largest reservoir of fresh water on the planet. In fact, they store 75% of the world's fresh water!

6.
The world's largest glacier is Lambert Glacier, located in Antarctica, measuring approximately 100km wide, 400km long and 2.5km deep!

7.
Mountain valleys are typically "V" shaped before being taken oven by a glacier; during glaciation, the valley widens and deepens and thus becomes "U" shaped.

8.
The Kutiah Glacier in Pakistan has the record for the fastest glacier surge. In 1953, it moved more than 12km in three months.

9.
Earth's two ice sheets cover most of Greenland and Antarctica and make up more than 99% of the world's glacial ice.

10.
The Antarctic ice sheet is actually a glacier and has existed for at least 40 million years.

11.
Glaciers are found in 47 countries.

12.
Alaska is estimated to have more than 100,000 glaciers. Most remain unnamed.

13.
A single glacier ice crystal can grow to be as large as a baseball.

14.
On steep slopes, a glacier can be as thin as 50 feet.

15.
A glacier can range in length from the equivalent of a football field to more than 100 miles.

16.
Though it sits on the equator, Mount Kilimanjaro is glaciated.

17.
If climate change caused the Antarctic ice sheet to melt entirely, it is estimated that sea levels would rise by around 65m. That means that London would be lost underwater!

18.
Glacial ice can be hundreds of thousands of years old, which makes it a valuable resource for assessing climate change. By extracting and analysing the ice, scientists can learn about what the climate was like on Earth thousands of years ago!

Sources
National Geographic Kids / World Wildlife Fund