SNOWPITS and AVALANCHES:
Snowpits are dug to assess snowpack safety. As mentioned elsewhere, it is best to get a book like Staying Alive in Avalanche Terrain by Bruce Tremper and studying it before much else. As new snow is deposited first on the ground and then on successive layers of snow it bonds at different rates and to different degrees. Avalanches are produced when layers do not bond well and gravity combined with weight allow overlaying snow to release on a steeper slope from the underlying surface. Tthe snowslab fails and slides down the mountain on a slope usually between 28-45 degrees with 38 the most prevalent angle.
Avalanches are often triggered by humans. The extra weight on a trigger spot allows the snow to collapse quickly and therefore fail and begin to slide. Windloading, buried surface hoar, crusts, recent heavy snowfall, RAIN, and rapid warming and cooling are all conditions that should make you extra alert and cautious when it comes to traveling in avalanche terrain.
measuring slope angle *** **
Digging snowpits and looking for instabilities requires not only specialized knowledge but specialized equipmet as well.
Everyone should carry a shovel and probe both helpful in digging and measuring a pits depth. Probes are good for checking depth in many locations as well as provide a sensitive tool for probing for crusts, hard layers, soft layers and inconsistencies in the snowpack. An inclinometer is necessary to measure the slope angle of your pit as well as the slopes on which you plan to travel and play. A rite in the rain notebook allows notetaking in any conditions alongwith a pencil, preferable mechanical. A soft paintbrush is helpful to brush the walls of the pit to find crusts, and hard and weak layers. A snow thermometer is used to measure the snowpack at regular 10 cm intervals to determine the temperature gradient and whether the snow pack is gaining strength and where and where it is losing strength. A snowsaw allows the avalanche detective to isolate columns of snow to perform stability tests on the column. There is the shear test, the compression tap test, the stuffblock test, the Rutschblock test, and the tap test. When digging pits it is important to dig them in a representative area to what you are planning to ski; therefore bringing a short rope and belaying the pit meister onto a steep slope can be a safe way to gauge more dangerous terrain. However ropes have been known to break and do not tie knots that will tighten around the pit meister should he be caught in a slide.
I am recommending again the purchase of a couple good books on the subject reading them and doing a lot of field work before deciding that you can safely determine conditions. Pay attention to the forecasters local to your area and stear clear of dangerous slopes when stability is poor. It could save your life or your good friends or partners.