Powder Avalanche

• Powder-Avalanche-0.mp3
• Powder-Avalanche-0.mp4
• Powder-Avalanche-Best-of-Best-of.mp3
• Powder-Avalanche-Best-of-Best-of.mp4
• Powder-Avalanche-I.mp3
• Powder-Avalanche-I.mp4
• Powder-Avalanche-Unplugged-Underground-XIII.mp3
• Powder-Avalanche-Unplugged-Underground-XIII.mp4
• Powder-Avalanche-Unplugged.mp3
• Powder-Avalanche-Unplugged.mp4
• Powder-Avalanche-intro.mp3

[Intro]
Woah (oh)
The power
Of powder
(Don’t ya know)
Watch ‘er blow

[Verse 1]
(Air blast)
Moving past
(Moving past fast)
Nothing lasts

[Chorus]
Flattening forests
(Flattening structures)
In the way, laid to rest
(Frozen ’til rapture)

[Bridge]
Woah (oh)
The power
Of powder
(Don’t ya know)
Watch ‘er blow

[Verse 2]
A turbulent mix
(Snow and air betwixt)
Behave as a fluid
(Turning do to did)

[Chorus]
Flattening forests
(Flattening structures)
In the way, laid to rest
(Frozen ’til rapture)

[Bridge]
Woah (oh)
The power
Of powder
(Don’t ya know)
Watch ‘er blow

[Outro]
Caught in the flow…
(Gotta go) Go! Go! Go!

A SCIENCE NOTE

Physics of an Avalanche

An avalanche is a rapid flow of snow, ice, and debris down a slope, driven by gravity and influenced by mechanics, fluid dynamics, and thermodynamics. Here’s an explanation of the key physics involved:
1. Initiation: What Triggers an Avalanche

Shear Stress vs. Shear Strength

• Shear Stress ($\tau$): The force per unit area parallel to the slope acting on the snow layer: $\tau =\rho \cdot g\cdot h\cdot \sin (\theta )$,
  where:
  • $\rho$ = snow density,
  • $g$ = acceleration due to gravity,
  • $h$ = snow layer thickness,
  • $\theta$ = slope angle.
• Shear Strength (τmaxτ_{\text{max}}τmax​): The resistance of the snowpack to sliding, determined by cohesion between snow grains and friction with the slope.

Avalanches occur when τ>τmaxτ > τ_{\text{max}}τ>τmax​, meaning gravitational forces exceed resistance.

Triggers

• Natural: Additional snow, temperature changes, or vibrations (e.g., earthquakes).
• Human: Skiers, climbers, or explosions creating localized stress.

---

2. Propagation: Snow Layer Collapse

Fracture Mechanics

• When shear stress exceeds shear strength, cracks form in the weak snow layer. These cracks spread quickly, causing the overlying snow to lose support and start sliding.

Release Zone

• The initial area where snow breaks free is the “release zone.” Its size and shape determine the avalanche’s potential energy.

---

3. Movement: Avalanche Dynamics

Avalanches can behave like solids, fluids, or a mix depending on type and stage of motion.

Types of Avalanches

1. Slab Avalanche: A cohesive snow layer slides as a block before breaking apart.
2. Loose Snow Avalanche: Starts at a point, gathering material as it descends.
3. Powder Avalanche: A turbulent mix of snow and air behaving like a fluid.

Forces in Motion

• Gravitational Force (FgF_gFg​): Drives snow downhill:
  Fg=m⋅g⋅sin⁡(θ)F_g = m \cdot g \cdot \sin(θ)Fg​=m⋅g⋅sin(θ),
  where $m$ = snow mass.
• Frictional Force (FfF_fFf​): Resists motion, depends on slope and snow type:
  Ff=μ⋅m⋅g⋅cos⁡(θ)F_f = μ \cdot m \cdot g \cdot \cos(θ)Ff​=μ⋅m⋅g⋅cos(θ),
  where $\mu$ = friction coefficient.
• Drag Force (FdF_dFd​): Opposes motion and increases with velocity in powder avalanches:
  Fd=0.5⋅Cd⋅ρ⋅A⋅v2F_d = 0.5 \cdot C_d \cdot ρ \cdot A \cdot v^2Fd​=0.5⋅Cd​⋅ρ⋅A⋅v2,
  where CdC_dCd​ = drag coefficient, $A$ = cross-sectional area, $v$ = velocity.

---

4. Energy Considerations

Potential Energy to Kinetic Energy

• Snow at rest has potential energy ($PE$):
  $PE=m\cdot g\cdot h$.
• As it moves, this converts to kinetic energy ($KE$):
  KE=0.5⋅m⋅v2KE = 0.5 \cdot m \cdot v^2KE=0.5⋅m⋅v2.

Thermal Energy

• Friction and collisions generate heat, melting some snow and influencing flow behavior.

---

5. Deposition: Avalanche Runout

Stopping Mechanisms

• Frictional Dissipation: Friction eventually overcomes gravitational force.
• Terrain Flattening: Reduces slope angle and shear stress.
• Obstacle Interaction: Trees, rocks, or barriers disrupt flow.

Runout Distance

• Determined by initial energy, mass, and terrain. Larger avalanches with higher momentum travel farther.

---

6. Avalanche Effects

Impact Force

• The impact force (FimpactF_{\text{impact}}Fimpact​) on structures is massive:
  Fimpact=m⋅v/ΔtF_{\text{impact}} = m \cdot v / ΔtFimpact​=m⋅v/Δt,
  where $\Delta t$ = time of impact.

Air Blast

• Powder avalanches create air blasts capable of flattening forests and structures.

---

Conclusion
Avalanches demonstrate the interplay of gravity, friction, and fluid dynamics. Their destructive power comes from rapid conversion of potential energy to kinetic energy and the dynamic behavior of snow as it transitions between solid and fluid states. Understanding these physics helps predict and mitigate avalanche risks.

From the album “Snowball Effect” by Δ To Cause a Change

The Human Induced Climate Change Experiment

MegaEpix Enormous