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The difference between these two concepts is subtle but important. The landslide causes are the reasons that a landslide occurred in that location and at that time and may be considered to be factors that made the slope vulnerable to failure, that predispose the slope to becoming unstable. The trigger is the single event that finally initiated ...
During the warm late Eocene, sea levels were high, and the tidewater region of Virginia lay in the coastal shallows. The shore of eastern North America, about where Richmond, Virginia is today, was covered with thick tropical rainforest, and the waters of the gently sloping continental shelf were rich with marine life that was depositing dense layers of lime from their microscopic shells.
The geology of Virginia began to form at least 1.8 billion years ago. The oldest rocks in the state were metamorphosed during the Grenville orogeny , a mountain-building event beginning 1.2 billion years ago in the Proterozoic , which obscured older rocks.
A landslide in which the sliding surface is located within the soil mantle or weathered bedrock (typically to a depth from few decimeters to some meters) is called a shallow landslide. Debris slides and debris flows are usually shallow. Shallow landslides can often happen in areas that have slopes with high permeable soils on top of low ...
A landslide, also called a landslip, [10] is a relatively rapid movement of a large mass of earth and rocks down a hill or a mountainside. Landslides can be further classified by the importance of water in the mass wasting process. In a narrow sense, landslides are rapid movement of large amounts of relatively dry debris down moderate to steep ...
Downhill creep, also known as soil creep or commonly just creep, is a type of creep characterized by the slow, downward progression of rock and soil down a low grade slope; it can also refer to slow deformation of such materials as a result of prolonged pressure and stress.
It is an intermediate type of mass wasting that is between downhill creep and mudflow. The types of materials that are susceptible to earthflows are clay, fine sand and silt, and fine-grained pyroclastic material. [1] When the ground materials become saturated with enough water, they will start flowing (soil liquefaction). Its speed can range ...
Sudden slumps usually occur after earthquakes or heavy continuing rains, and can stabilize within a few hours. Most slumps develop over comparatively longer periods, taking months or years to reach stability. An example of a slow-moving slump is the Swift Creek Landslide, a deep-seated rotational slump located on Sumas Mountain, Washington.