DRRR-L1-4th-quarter

Geological Hazards

Objective

• Identify the causes of geological hazards at the end of the lesson.

Examples of Geological Hazards

• Landslides

  • Reference: Baguio Landslides (Figure 1)

• Sinkholes

  • Reference: Negros Oriental Sinkhole (Figure 2)

Natural Causes of Landslides

• Earthquake

  • Seismic activities disrupt friction maintaining sediment stability; may cause cracks for water infiltration.

• Heavy Rainfall

  • Weaken friction between bedrock and sediments, carrying debris downhill.

Other Natural Causes of Landslides

• Wildfire

  • Destroys vegetation that stabilizes soil, leading to soil instability.

• Volcanic Eruption

  • Ash deposits and lahar formation due to water mixing with volcanic material.

Human Causes of Landslides

• Clear Cutting

  • Full removal of trees destabilizes soil binders.

• Mining/Construction

  • Destroys bedrock and weakens soil foundations.

Other Causes of Landslides

• Influence of Slope

  • Steeper slopes are more prone to landslides.

• Lithology

  • Composition of rocks (e.g., clay, mica) affects weathering and landslide risk.

Natural Causes of Sinkholes

• Earthquake

  • Vibration causes rock breaks allowing groundwater to dissolve minerals.

• Water

  • Dissolves minerals, creating gaps in rocks.

• Groundwater

  • Reduced groundwater support can lead to collapse of soft materials.

Human Causes of Sinkholes

• Heavy Loads on Surface

• Drilling & Mining

• Broken Water/Drainpipes

• Deep Excavation

Effects of Landslides/Sinkholes

• Loss of lives

• Destruction of infrastructure

• Loss of natural resources

• Decrease in property value

• Medical costs

• Loss of water availability

Classification Exercise

• Write "NC" for Natural cause and "HC" for Human cause in provided scenarios:

  1. Magnitude 6.7 earthquake in Baguio City

  2. Mining of gold in Sierra Madre

  3. Taal volcano eruption in 2020

  4. Typhoon Ondoy (2019)

  5. Tree cutting in Pampanga

  6. Wildfire in Canada

  7. Kaingin system in Davao

  8. Road construction on MacArthur Highway

  9. Deep excavation in Benguet

  10. Building construction in Manila