Avalanche Awareness: Part 1 - What Are Avalanches? Types - Causes - Risks
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Avalanche Awareness: The Ultimate Backcountry Safety Course
Everything You Need to Know About Avalanche Danger: A 7-Part Backcountry Safety Course - Part One
Backcountry travel offers some of the most rewarding mountain experiences, from carving pristine powder to summiting breathtaking peaks. But with these adventures come real risks, and avalanches are among the deadliest hazards you can face. Whether you’re skiing, snowboarding, hiking, or mountaineering, understanding avalanche safety is not optional—it’s essential.
This 7-part course is designed to provide you with a comprehensive understanding of avalanche danger in the backcountry. Through these chapters, you’ll gain the tools, knowledge, and confidence to navigate avalanche terrain safely.
By the end of this course, you will have learned:
- What avalanches are, why they happen, and the different types to watch for.
- How to recognise avalanche-prone terrain and avoid it.
- How weather and snowpack conditions affect avalanche risk.
- How to properly use avalanche safety gear—and why practice is critical.
- Best practices for traveling in avalanche terrain to minimise risk.
This isn’t just a guide; it’s a resource to help you stay alive in the mountains. Knowing this information and practicing it could save your life or the lives of others in your group.
The Seven Chapters
Each chapter of this course covers an essential aspect of avalanche safety. Together, they form a complete foundation for making informed decisions in the backcountry:
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What Are Avalanches? Types, Causes, and Risks
Learn the science behind avalanches, the different types, and why understanding their causes is critical for recognising danger. -
Essential Avalanche Equipment: Your Lifeline in the Backcountry
Discover the gear you need to carry, how to use it effectively, and why regular practice is essential for rapid, efficient rescues. -
Recognising Avalanche Terrain: A Critical Skill for Backcountry Safety
Understand how terrain influences avalanche risk and learn how to make safer route choices to minimise exposure. -
Field Observations and Snowpack Testing: Assessing Stability in Avalanche Terrain
Explore how to read the snowpack and conduct tests in the field to better understand stability and predict potential danger. -
How Weather Affects Avalanche Risk
See how snowfall, wind, temperature changes, and rain interact with the snowpack to create or reduce risk. -
Understanding Avalanche Danger Ratings and Why “Moderate” Isn’t Safe
Decode avalanche danger ratings and learn why “Moderate” or “Considerable” levels don’t mean low risk—and how to use this information for planning. -
Best Practices for Avalanche Safety
Master the techniques and strategies for traveling safely in avalanche terrain, from group communication to adaptability and route planning.
Why Take the Time to Learn?
Avalanches aren’t random—they follow patterns and are influenced by conditions that you can learn to identify and understand. But knowledge alone isn’t enough. Backcountry safety also requires preparation, regular practice, and a commitment to making conservative, safety-first decisions.
This course provides the foundation you need to start making informed choices in avalanche terrain. However, it’s no substitute for hands-on learning—consider taking an in-person avalanche safety course and practicing with your gear regularly to keep your skills sharp.
The mountains demand respect, and understanding avalanche safety is one of the most important ways to honour that. So, let’s get started on this 7-part journey to safer backcountry exploration.
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Let's get started:
What Are Avalanches? Types, Causes, and Risks
Avalanches are one of the most dangerous natural hazards in the mountains. They occur when the snowpack—a layered accumulation of snow—loses stability, causing one or more layers to slide downhill. Avalanches are not random; they follow predictable patterns that can be understood, mitigated, and avoided with the right knowledge and tools.
How Fast and Powerful Are Avalanches?
Avalanches can accelerate to speeds of 60–80 mph (100–130 kph) within seconds, making escape nearly impossible once you’re caught. They can carry hundreds of tons of snow, ice, and debris, crushing anything in their path. Even a small avalanche can bury a person under compacted snow so dense that digging out by hand is nearly impossible.
Understanding the types of avalanches, their causes, and how they behave is critical for recognising and avoiding danger.
Types of Avalanches
1. Slab Avalanches- What They Are: Slab avalanches occur when a cohesive layer of snow (the slab) fractures and slides downhill on a weaker layer below. These avalanches are by far the most dangerous, accounting for nearly 90% of all avalanche fatalities.
- Causes:
- Human activity is the most common trigger, such as a skier or snowboarder disturbing the snowpack’s balance.
- Natural causes like wind-loading or additional snowfall exceeding the snowpack’s stability threshold.
- Characteristics:
- Fracture Line: A distinct break at the top of the slide, often spanning wide areas of the slope.
- Propagating Fractures: The initial fracture can spread across an entire slope, causing massive slides.
- Speed: Can reach over 80 mph in seconds, making escape almost impossible once triggered.
Real-Life Example: A skier crosses a steep, leeward slope after a storm. The added weight of their movement triggers a slab avalanche that sweeps down into a gully, burying them and another skier in their group.
Watch below: A snowboarder triggers a large slab avalanche.
2. Loose Snow Avalanches
- What They Are: Also called “point-release avalanches,” these start from a single point—often the result of a skier, snowboarder, or natural event like falling ice. They gather loose snow as they descend, creating a fan-shaped slide.
- Causes:
- Triggered in light, dry, and unconsolidated snow, often on very steep terrain (40° or more).
- Characteristics:
- Smaller in scale compared to slab avalanches.
- Typically less destructive but still dangerous, especially if they carry a person into hazardous terrain (e.g., cliffs, gullies).
Real-Life Example: A mountaineer ascending a couloir triggers loose snow near the top. The avalanche carries them a short distance, but they manage to stop before falling into a crevasse.
3. Wet Avalanches
- What They Are: These occur when water saturates the snowpack, significantly weakening it. Wet avalanches are more common during periods of warming, such as springtime or after heavy rain.
- Causes:
- Warm temperatures melting surface snow.
- Rain-on-snow events adding weight and reducing friction between snow layers.
- Characteristics:
- Slower-moving than dry avalanches, often traveling between 10–20 mph.
- Extremely heavy due to high water content, causing more destruction despite their slower speed.
Real-Life Example: During an unusually warm spring day, a wet avalanche releases naturally on a sunny slope, sweeping away trees and debris.
4. Cornice Collapses
- What They Are: Cornices are large overhanging masses of snow that form along ridgelines due to wind. When they collapse, they can trigger avalanches below.
- Causes:
- Strong winds depositing snow unevenly on the leeward side of ridges.
- Sudden warming or additional snow load causing the cornice to break.
- Characteristics:
- Difficult to see from above, making them particularly dangerous for skiers or climbers traveling along ridge-lines.
- Can trigger both slab and loose snow avalanches on slopes below.
Real-Life Example: A climber unknowingly steps too close to a cornice. It collapses under their weight, triggering a large avalanche down the slope beneath.
5. Glide Avalanches
- What They Are: These occur when an entire snowpack slides slowly downhill due to a lubricating layer of water at the ground level. Glide avalanches are unique because they can move gradually for hours or days before releasing suddenly.
- Causes:
- Warm weather or rain increasing water content at the snow/ground interface.
- Smooth ground surfaces, like grass or rock slabs, reducing friction.
- Characteristics:
- Often occur on smooth, grassy, or rocky slopes.
- Difficult to predict; the snowpack can release suddenly after days of slow movement.
Real-Life Example: A backcountry skier spots long cracks in the snowpack above a grassy slope. Later that afternoon, the entire slope releases in a glide avalanche, leaving a large wet scar.
Why Do Avalanches Happen?
The key to understanding avalanches lies in recognising the delicate balance between the snowpack, terrain, and external forces:
- Snowpack Instability: Weak layers in the snowpack (caused by weather changes, wind-loading, or temperature gradients) reduce stability.
- Slope Angle: Slopes between 30° and 45° are most prone to avalanches.
- Triggers: Additional stress—such as a skier’s weight, fresh snowfall, or rapid warming—can push an unstable snowpack past its tipping point.
How Dangerous Are Avalanches?
Avalanches are one of the leading causes of fatalities in the backcountry. Key dangers include:
- Burial: Victims can be buried under heavy, compacted snow, making self-rescue nearly impossible.
- Trauma: Many fatalities result from collisions with rocks, trees, or other debris.
- Hypothermia: Even if a victim survives burial, the cold environment can quickly lead to life-threatening conditions.
Key Takeaway
Understanding avalanche types and their causes is the first step in staying safe in the backcountry. By recognising warning signs, assessing terrain carefully, and carrying the proper gear, you can significantly reduce your risk of being caught in an avalanche. In the next sections, we’ll dive deeper into spotting hazards, testing snow stability, and responding effectively if an avalanche occurs.
Ready to follow onto the next lesson? Click here for chapter 2 - Essential Avalanche Equipment: Your Lifeline in the Backcountry