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• Geological hazards are natural phenomena that cause major problems around the world. The expansion and development of cities has led to an increase in impact and damage due to geological hazards. In general, most of the geological hazards are related to natural conditions, although some may be due to human activities. 
• landslides come in various names such as mudslide, flash flood, avalanche, etc. The actual difference is in their composition provided that there is an inclined terrain.
• Sinkhole occur elevated or flat surfaces and can range from massive to barely noticeable which may leave a dent, a hole, or a body of water on the ground.
•  landslide is a ground

  movement on a sloping terrain. It does not happen on flat ground

  because of the angle on

  the ground, gravity

  induces the land to

  move downward. It is

  aggravated by rain

  because water is a

  natural agent for erosion.

  If rain or any source of water frequently flows down a sloping area thegravitationaldescent

  of loosened soil makes it possible for landslide to occur. 
• Structures that are built on steep-slope mountains have a high vulnerability to landslide hazards especially during heavy rains. Areas with: steep slope, dense population and denuded terrain are distinguished by a high susceptibility to rainfall-induced landslide hazards. Long or regular rain may saturate the topsoil and the bedrock, weakening the soil base of buildings or structures.
• Slumping Landslide is a downward movement of rock debris, usually the consequence of removal of buttressing earth at the foot of a slope of unconsolidated material
• Debris Flow Landslide happens when the slope becomes saturated with water, this then triggers a landslide of water-soaked mass of rock and soil that slides down the slope.
• Rock Fall landslides are sudden slides 

  caused by heavy rain the rock on the slope loosens and then slides down the slope
• sinkhole is a topographic depression created when groundwater dissolves the underlying limestone bedrock. Often known as "sink" or "doline,".
• Characteristics:

  • occur in areas where the soil foundation is made of soft minerals and rocks such as limestone, salt beds, or any acidic rocks.
  • The depth of sinkholes ranges from a couple of meters to several mile deep.
• Sinkhole - Water from the rainfall seeps underneath the soil through the cracks and fissures.
• Cover Collapse Sinkhole It develops suddenly (over an hour period) thus, causing catastrophic damage.
• Cover Subsidence Sinkhole It gradually grows where the sediment covers are permeable and contain sand.
• 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.
• Artificial Sinkhole Such types of sinks may be caused by various human activities, including groundwater pumping and building
• NATURAL CAUSES OF LANDSLIDES

  Climate

  Earthquake

  Weathering

  Erosion

  Volcanic eruption

  Forest fire

  Gravity
• Human causes of lanslides

  Mining

  Clear cutting
• Climate - Long-term climatic changes can significantly impact soil stability. A general reduction in precipitation leads to lowering of water table and reduction in overall weight of soil mass, reduced solution of materials and less powerful freeze-thaw activity. A significant upsurge in precipitation or ground saturation would dramatically increase the level of ground water. When sloped areas are completely saturated with water, landslides can occur. If there is absence of mechanical root support, the soils start to run off.
• Earthquake - Seismic activities have, for a long time, contributed to landslides across the globe. Any moment tectonic plates move, the soil covering them also moves along. When earthquakes strike areas with steep slopes, on numerous occasion, the soil slips leading to landslides In addition, ashen debris flows instigated by earthquakes could also cause mass soil movement.
• Weathering - It is the natural procedure of rock deterioration that leads to weak, landslide-susceptive materials. It is brought about by the chemical action of water, air, plants and bacteria. When the rocks are weak enough, they slip away causing landslides.
• Erosion caused by sporadic running water such as streams, rivers, wind, currents, ice and waves wipes out latent and lateral slope support enabling landslides to occur easily. 
• Volcanic eruption an eruption occurs in a wet condition, the soil will start to move downhill instigating a landslide. Stratovolcano is a typical example of volcano responsible for most landslides across the globe. Volcanic gases partially dissolve in groundwater which turns into acidic hydrothermal systems that weakens rock by altering minerals to clay.
• Forest fire Burns vegetation that holds soil in place. Since it takes time for vegetation to re establish on steep slopes, the risk of landslides prevails or up to 20 years in dry climates. Wildfire removes the protective ability of vegetation which increases runoff, erosion, and debris flow because the water cannot penetrate through the soil thus carrying the debris downslope. burrowing insects also play a role by aerating the soil destabilizing it during a wildfire because they tend to seek for cooler 

  soil to survive.
• Gravity Steeper slopes coupled with gravitational force can trigger a massive landslide. Steeper slopes can also cause the debris to move farther from the foot of the area.
• Mining activities that utilize blasting techniques contribute mightily to landslides. Vibrations emanating from the blasts can weaken soils in other areas susceptible to landslides. The weakening of soil means a landslide can occur anytime. Earthwork alters the shape of a slope, 

  imposing new loads on an existing slope.
• Clear cutting is a technique of timber harvesting that eliminates all old trees from the area. This technique is dangerous since it decimates the existing mechanical root structure of the area. It changes the amount of water infiltrating the soil.
• Rainfall-Induced landslides are the most common and widespread damaging landslides in the Philippines, with an average of 20 typhoons each year due to prolonged or heavy rainfall. Most rainfall-induced landslides are shallow (less than a few meters deep), thin, and move quickly.
• Natural causes of sinkhole Dissolution sedimentary rock
• Human cause sinkhole - underground water pumping
• – Dissolution of sedimentary rocks

  -Sinkholes occur when sedimentary rocks are dissolved. When these rocks are dissolved, it can either form a void of water or air. A void filled with air forma a hole and a void filled with underground water makes a lake or a pond. Sinkholes can be in the form of holes or depressions on the groun
• – Underground water pumping

  -Pumping water underneath the ground causes drainage to alter their flow which causes the soil to be eroded by water. Broken pipes underneath the ground can also cause internal erosion making a void underneath the ground. Altering drainage systems cause water to branch into other routes where there is soluble rock can cause erosion through the flow of water.
• Cover Collapse Sinkhole

  Develop abruptly (over a period of hours) and thus cause catastrophic damages. 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.
• Cover Subsidence Sinkhole

  Develop gradually where the covering sediments 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.
• Dissolution Sinkhole

  Occur in areas where limestone is exposed at land surface or also is covered by thin layers of soil and permeable sand. 

  Dissolution of the limestone or dolomite is most intensive where the water first contacts the rock surface. Aggressive dissolution also occurs where flow is focused in pre-existing openings in the rock, such as along joints, 

  fractures, and bedding planes, and in the zone of water-table fluctuation where groundwater is in contact with the atmosphere
• Artificial Sinkhole

  These types of sinkholes can be caused by various human activities, including groundwater pumping and construction activities. However, the most common 

  activities that result in artificial sinkholes are mining, drilling, considerable changes in weight, as well as a tremendous increase in water flow, such as a construction of an artificial pond.
• Signs of impending landslides

  1.Earlier landslides as indicater

  2.Tension cracks

  3.Things moving

  4.water doing something different
• 1. Earlierlandslide as indicater - occurence of landslides soil in area is weak and unstable geology
• 2. TENSION CRACKS - Stress friction, locate high elevated ground
• 3. Things moving - deformation and movement non living object
• 4. Water doing something different - change water flow