The 1980 Mount St. Helens landslide was about a million Olympic pools of debris.

The 1980 eruption didn't just make Mount St. Helens shorter. The collapsed summit and north side became an enormous debris avalanche — that's part of where the missing mountain went.

USGS gives the total avalanche volume as about 2.5 km³ (3.3 billion cubic yards), and itself compares that with about 1 million Olympic swimming pools.

Our own Olympic-pool reference is 2,500 m³, which gives the same answer: 2.5 km³ is 2.5 billion m³, divided by 2,500 m³ is about 1 million.

This is a volume comparison. No pools held the debris, and real Olympic pools don't all hold the same amount of water.

Debris avalanche volume

≈2.5 km³Source value

USGS estimate

In cubic metres

2,500,000,000 m³Calculated

Olympic-pool reference

2,500 m³Reference value

Scaleidoscope's 50 × 25 × 2 m reference

Pools

2,500,000,000 ÷ 2,500 = 1,000,000Calculated

Published

≈1 million reference poolsResult

Matches USGS's own comparison

Approximate calculated comparison. 2.5 km³ is a USGS estimate, and the Olympic pool is a stated reference volume rather than one fixed real-world amount.

USGS gives the debris avalanche as approximately 2.5 km³; the displayed result is rounded.

• USGS

  Mount St. Helens debris-avalanche volume(opens external site)

• USGS

  1980 Cataclysmic Eruption(opens external site)

  Total avalanche volume about 2.5 km³

• Scaleidoscope

  Scaleidoscope derived calculation from sourced official dimensions

  Scaleidoscope arithmetic from the sourced inputs

• Scaleidoscope

  Scaleidoscope derived calculation from sourced official dimensions

  Scaleidoscope arithmetic from the sourced inputs

• USGS

  1980 Cataclysmic Eruption(opens external site)

  Equivalent to 1 million Olympic swimming pools

• Measurement trap🏊An “Olympic-size pool” doesn’t have one universal exact volume.

• How much volcano is a volcano?🗻Mount Fuji is roughly 160–200 million Olympic-pool reference volumes.
• Can a mountain lose height?🌋Mount St. Helens became about 400 metres shorter in a day.
• Same amount☕About 5.3 million Starbucks Grandes.
• Same amount🥤About 2.1 million 40-oz Stanley Quenchers.
• Measurement trap🏊An “Olympic-size pool” doesn’t have one universal exact volume.
• Things in things🏓About 1.3 million.