A hoar frost are ice crystals that can form at ground level or above it, they can form in the air, in crevasses, in the deepness of glaciers and can be the major cause of avalanches under the right environment. Hoar frost has to have the precise conditions to form and this comes in the appearance of moisture and temperature.
Hoar frost usually forms on freezing clear nights when the heat of the earth disappears into the skies and causes the earth to grow a lot colder than the atmosphere around it. There are many names given to hoar frost and for any type of hoar frost to form it is imperative that at the point of the frost the temperature is at freezing or below.
Most people think that hoar frost is frozen dew but hoar frost has a life of its own starting as minute ice crystals that can form on the ground. These crystals will grow larger which is called true hoar frost crystals. For hoar frost to grow it needs cold conditions and vapor in the air. Hoar frost on average will not hang around very long as the heat of the day will melt it very easily.
Surface hoar frost
This perhaps is the most basic and common hoar frost. The crystals usually form on top of the snow and is easily seen in the morning as it makes the snow very sparkly and shiny. However this type of hoar frost forms differently those others by melting in the heat of the day and refreezing during the cold temperatures of the night.
The cold temperatures cause the outside of the snow to freeze more than the inside. A process now takes place where the moisture dries up inside the bank of snow and reforms on the top. This type of frost can grow quite large and be very easily seen in the early morning but again once the sun comes up the frost quickly disappears. Surface hoar frost can be dangerous especially high in the mountains. It can cause avalanches to occur without much warning.
Air hoar frost
Air hoar frost is the frost you can see forming on trees, branches or any object that is on top of the surface. This type of hoar frost can be magical when attached to objects. It will outline the finest twigs of a tree as well as the tree itself. This type of hoar frost is extremely fragile and is formed from ice crystals as all hoar frost is. The moisture level needs to be high and the temperature cold to form this type of frost.
Crevasse hoar frost
Crevasse hoar frost is not often seen as it develops deep into the crevasses of snow in glaciers. It is somewhat different than exposed hoar frost as it lies in areas where the weather cannot influence its growth. This type of hoar frost happens when deep under the snow and ice water vapor accumulates without interference. Crevasse hoar frost can be seen in caves if the moisture content and temperatures are right.
Depth hoar frost
Depth hoar frost is very similar to crevasse hoar frost but the name refers to the shape of the frost which is cupped shape. Depth hoar frosts are crystal that forms under dry snow. These are just as dangerous as they are weak crystals and being under the snow always presents the problem of movement.
Hoar frost can be beautiful whether it forms on trees, windows or any object. It has a tendency to change anyone’s perspective of the object when they see it. Winter does have some perks and hoar frost is one of them, so much so that you will tend to forget how cold it is outside. You can really appreciate this occurrence once you know what hoar frost is.