lesson 10-11

• geological hazard - is an adverse geological condition capable of causing widespread damage or loss of property and life.
• mass wasting - downslope movement of rock, regolith, and soil under the direct influence of gravity. It does not require transporting medium.
• gravity - the controlling force of mass wasting.
• mass wasting

  trigger - an event that initiates downslope movement.
• mass wasting

  angle of repose - the steepest angle at which a material remains stable.
• mass wasting

  liquefaction - Process where water-saturated surface material loses their strength and behave as fluidlike masses that flow.
• type of motion

  flow - Material moves downslope as a viscous fluid.
• type of motion

  fall - Freefall of detached individual pieces of any size.
• type of motion

  slide - A distinct zone of weakness separating the slide material from the more stable underlying material.
• type of motion: flow

  earthflow - a type of mass wasting that leaves a scar on the slope of a hillside and forming a tongue- or teardrop-shaped mass that flows downslope.
• type of motion: flow

  Debris Flow - a relatively rapid type of mass wasting that involves a flow of soil and regolith containing a large amount of water.

  • Mudflow - when the material is primarily fine-grained.
  • Lahar - debris flow composed mainly of volcanic material on the flanks of volcanoes.
• type of motion: fall

  Talus Slope – a cone-shaped accumulation of broken rock fragment that fall to the base of the cliff.
• type of motion: fall

  Rock Fall - quantity/sheets of rock that has fallen freely from a cliff face.
• type of motion: fall

  Avalanche - rock and debris that hurtle downslope at speeds exceeding 200kph.
• type of motion: slide

  Landslide – movement of consolidated rocks, debris, and soil due to gravity
• type of motion: slide

  Mudslide - movement of mud due to gravity
• type of motion: slide

  Rockslide - movement of rocks due to gravity
• type of motion: slide

  Slump - downward sliding of a mass of rock or unconsolidated material moving as a unit long a curved surface.
• rate of movement: rapid

  • Slump
  • debris flow - mudflow, lahar
• rate of movement: rapid

  • earthflow
  • landslide
  • rock slide
  • debris slide
• rate of movement: slow

  • creep – a type of mass wasting that is imperceptibly slow.
  • solifluction – a type of mass wasting that is common wherever water cannot escape from the saturated surface layer by infiltrating to deeper levels.
• landslide - is the mass movement of rock, soil, and debris down a slope due to gravity. It occurs when the driving force is greater than the resisting force.
• landslide mitigation - Actions taken to prevent or reduce the risk to life, property, social and economic activities, and natural resources from natural hazards.
• landslide triggers

  • • Natural triggers
  • • Intense rainfall
  • • Weathering of rocks
  • • Ground vibrations created during earthquakes
  • Volcanic activity
  • • Man-made triggers like mining and clear-cutting
• landslide triggering conditions

  • Steep Slopes
  • • Weakening of slope material
  • • Weathering of rocks
  • • Overloading on the slopes
• signs of impending landslide

  • earlier landslide as indicator
  • tension cracks
  • things moving
  • water doing something different
• engineering intervention measures

  • benching
  • retaining wall
  • gabion wall
  • shotcrete
  • drainage
  • erosion control
• sinkhole - is a topographic depression created when groundwater dissolves the underlying limestone bedrock. Often known as "sink" or "doline,".
• The only way to detect if an area is susceptible to sinkhole formation is through core drilling or groundpenetrating radar.
• types of sinkholes

  cover collapse sinkhole - It develops suddenly (over an hour period) thus, causing catastrophic damage. They occur where the covering sediments contain a significant amount of clay. Over time, surface drainage, erosion, and deposition of sinkhole into a shallower bowl-shaped depression
• types of sinkholes

  cover subsidence sinkhole - It gradually grows where the sediment covers are permeable and contain sand. In areas where cover material is thicker or sediments contain more clay, cover subsidence sinkholes are relatively uncommon and therefore may not be seen frequently. They are smaller and thus may go undetected for long periods.
• types of sinkholes

  dissolution sinkhole - It occurs in areas where calcareous is exposed on the ground or where thin layers of soil and permeable sand are also covered. Limestone or dolomite dissolution is most intense when the water first reaches the rock surface.
• types of sinkholes

  artificial sinkhole - Such types of sinks may be caused by various human activities, including groundwater pumping and building.
• earthquake - is a weak to violent shaking of the ground produced by the sudden movement of rock materials below the earth’s surface (PHIVOLCS).
• Fault lines - are cracks on the earth’s surface along which smaller plates move or slip against each other.
• focus - is point inside the earth where the earthquake started, sometimes called the hypocenter.
• epicenter - The point on the surface of the earth directly above the focus
• intensity - The strength of an earthquake as perceived and felt by people in a certain locality.
• magnitude - It is proportional to the energy released by an earthquake at the focus.
• types of earthquakes

  Tectonic earthquakes - are produced by sudden movement along faults and plate boundaries.