|theImage.com     Notes on Basic Geology|
|Notes created & information organization based on the book:
"The Dynamic Earth - an introduction to physical geology"
Brian Skinner & Stephen C. Porter   (further book information here)
also look at www.wiley.com for additional resource information
|Weathering - Page 5|
|Trigger the Mass Waste Process
Earthquakes or explosions (man made) may trigger earth movement in the form of landslides, slumps, or flows.
Changing the gradient of a slope my trigger any movement. Road cutting, pipe burial, home foundation making, and even some landscaping. These are man-made events which might cause a slide if they are done on or near the base of a gradient.
Water action against a stationary land mass that removes material at the base or even under the base. This can happen at the ocean with ocean waves removing material at the base of a cliff. It could happen at the outside turn in a stream as it cuts against material and removes it.
Heavy Rain Fall
If an area is subjected to above average rainfall, and especially if it happens in a short duration of time, then the normal run-off mechanisms may not be sufficient to remove the water.
Water can build up in the ground and add additional weight and lubrication. If underlying ground is impermeable, then the layers above may be free to slump or slide. The higher the gradient and the more porous the top material is, the more unstable the situation will become.
Water picks up velocity by moving swiftly downhill and energy by picking up sediments. Thus in a desert environment, flash flooding is quite dangerous even on relatively flat land. Debris filled water may rapidly move down steep canyons and then fill relatively shallow stream beds at high speed with added mass.
When a large volcano warms up even before eruption it may have sufficient energy to melt snow or glaciers on its side. The added water run-off is often sufficient to destabilize the steep gradient debris near the top and bring it down.
Unconsolidated ash from the current eruption or a previous eruption can be easily mobilized by new volcanic activity. Mud flows, or debris flows created by this mechanism are called Lahars.
Water pressure created by overlying sediment. As sediment builds it buries older sediment and the added pressure may squeeze water form the older sediment and create a rapid water flow.
Methane gas release from the ocean floor.