How Do Glaciers Form?
They need large masses of ice, particularly in polar regions or on higher ground. Glaciers are first formed by snow, which is the main form of solid precipitation. When hexagonal snowflakes pile up to a certain thickness, the snowflakes get pressed together in the shape of a snowball under high pressure. These are called firn. As new snow falls the old snow gets packed down. The shapes create a mass of solid ice. The melting and refreezing of the ice and the chipping away of the rocks create a large area for the ice. When the ice accumulates to around 100 metres in thickness, the ice at the bottom creates plasticity and it begins to move slowly. A glacier is born!
Formation The snow which forms temperate glaciers is subject to repeated freezing and thawing, which changes it into a form of granular ice called névé. Under the pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. In addition, a few hours after deposition, snow will begin to undergo metamorphism because of the presence of temperature gradients and/or convex and concave surfaces within individual crystals (causing differential vapour pressure). This causes the sublimation of ice from smaller crystals and the deposition of water vapour onto larger crystals, so many crystals become progressively more rounded over time. Depending on the type of metamorphism, the snowpack may become stronger or weaker as a result. The distinctive blue tint of glacial ice is often wrongly attributed to Rayleigh scattering which is supposedly due to bubbles in the ice. The blue col
The huge masses of ice flowing slowly over land are what we call glaciers. They form in high mountains and in polar regions, where large amounts of snow build up and freeze into ice. Snow falls in these places during the winter, but not all of it melts in the summer. The remaining snow builds up year after year in layers. As the
—Classified— Text Message #2: Tasks From: Crystal Subject: Your Tasks Time is running short!!! It is very important that you and your team embark on the Virtual Exploration. You’ll be traveling to the Worthington Glacier which is in the Chugach Mountains, in South Central Alaska. We’ll be in glacier country and will have a great opportunity to explore how glaciers are formed. Hurry, we must leave right away. We will: • Embark on our Virtual Exploration #1: How are Glaciers Formed? • Use the Online resources to learn more about how glaciers are formed. • Get Hands-On: Conduct a scientific experiment where you will apply the knowledge of glaciers that you have gained. • Use the “Spy Kids” assessment guide, to see how you are doing. Good Luck!!!
Glaciers develop over a period of centuries to thousands of years, when a combination of cold climate and abundant snowfall causes long-term snow accumulation to exceed summer melting. As the snowpack thickens, the deeper portions become compacted into glacial ice. The ice mass is plastic and reaches a point where it spreads (flows) outward under its own weight. Glaciers range from small alpine glaciers (which are mostly confined to valleys) to giant continental ice sheets such as those found today in Antarctica and Greenland.
