Look at a photo of our planet from space, and what you see is a relatively large ball of rock and water cloaked in a thin, tenuous atmosphere. The latter seems so insignificant compared with the solidity of the earth, yet its influence is crucial, and not just because of weather and climate.
Tides in the atmosphere, which are much like those in the sea, defined as they are by the gravitational influences of the Moon and Sun, could be triggering movement in the ground beneath our feet.
United States Geological Survey scientists Bill Schulz, Jason Kean and Gonghui Wang have discovered that landslides near Slumgullion Pass in Colorado tend to occur during the daily atmospheric low tide. The researchers compared hourly measurements of the slip speed of landslides over nine months with concurrent observations of local atmospheric pressure, and found a significant correlation.
Schulz and his colleagues say that effect could be caused by an upward movement of air and water molecules in the soil during periods of low atmospheric pressure, which reduces the friction that normally holds the earth in place. Pressure changes could trigger other geological phenomena that involve sliding surfaces, including earthquakes, volcanic eruptions and glacier movements.
Schulz et al., “Landslide movement in southwest Colorado triggered by atmospheric tides”, Nature Geoscience (2009)