Fourteen people have now been confirmed dead and another five injured following a landslide in the municipality of Rosas in the Valle del Cauca Department of Colombia. The incident happened early in the morning of Sunday 21 April 2018, following several weeks of heavy rain in the area. Landslides
are a common problem after severe weather events, as excess pore water
pressure can overcome cohesion in soil and sediments, allowing them to
flow like liquids. Approximately 90% of all landslides are caused by
heavy rainfall. The landslide is reported to have buried eight houses and a portion of the Pan-American Highway under several tonnes of mud, and rescue workers are still searching for more people potentially buried under the debris.
Rescue workers at the scene of the 21 April 2019 Rosas landslide. Camilo Fajardo/AFP.
Valle del Cauca area has a wet tropical climate with a double monsoon, which peaks in April and October. Such a double Monsoon Season is common close to the equator, where the Sun is highest overhead around the equinoxes and lowest on the horizons around the solstices, making the solstices the coolest part of the year and the equinoxes the hottest.
Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.
Monsoons
are tropical sea breezes triggered by heating of the land during the
warmer part of the year (summer). Both the land and sea are warmed by
the Sun, but the land has a lower ability to absorb heat, radiating it
back so that the air above landmasses becomes significantly warmer than
that over the sea, causing the air above the land to rise and drawing in
water from over the sea; since this has also been warmed it carries a
high evaporated water content, and brings with it heavy rainfall. In the
tropical dry season the situation is reversed, as the air over the land
cools more rapidly with the seasons, leading to warmer air over the
sea, and thus breezes moving from the shore to the sea (where air is
rising more rapidly) and a drying of the climate.
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