Rockfall

rockfall

Like most scientists, geologists are classifiers. We break all sorts of features into different groups based on their properties; soils, weather patterns, volcanoes, you name it we can classify it. This image is a particular type of a mass movement called a rockfall. Mass movements start with the basic rule of gravity – when something goes up it is likely to eventually come down. That rule obviously works on Earth, including with rocks that are built into mountains.

Rocks that have been thrust upwards in mountain ranges feel the force of gravity, but the resisting forces of chemical bonds that hold rocks together and the friction between one rock and another balance that force. When rocks are broken by eroding forces such as cracking due to ice and water flowing over them, they can break away and move. It is this process that determines what we call the resulting mass movement. If everything moves chaotically while the mass slides along the ground, it would be classified as an avalanche. If everything moving downward moves as a fast, coherent mass, without much shifting of the rocks and dirt in-between, that would be a slide (landslide, mudslide, etc.). Finally, if a single rock or a handful of rocks break away and bounce, spending most of their time in the air with nothing around them, that would be called a “rockfall”

This is a huge example of a rockfall from near Jalalabad in Afghanistan. The areas in Southeast Asia dominated by mountains are obviously a common site for any type of mass movement, including rockfalls. The combination of high peaks and in some areas high rainfall causes lots of material to become unstable every year, and there tends to be a peak in dangerous falls, slides, and avalanches in the summer and early fall, just as the heavy rains from the monsoon arrive. Source: Facebook

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