Geological Hazards

Geological Hazards

•Gradual or sudden natural earth process which causes:

•injury loss of life property damege

•loss of livehood and services

•social and economic disruption or

•environmental changes

1.LANDSLIDE

•falling down a sloping section of land

3 major of causes of landslide

1.GEOLOGY–the material of the soil or rock in the area.

2.MORPHOLOGY–the structure of the land.

3HUMAN ACTIVITY–agriculture and construction

Rainfall-induced Landslide

➤ occurs due to prolonged or heavy rainfall, increasing the weight of the land mass.

➤ The development may take several days but the landslide itself will only take a few minutes to cause a disaster.

➤ can form debris flows when they mix with additional water and sediments from their path. It may sweep away a whole community in an instant.

The impending signs of a rainfall-induced landslide.

➤ Unusual noises, such as breaking trees, or knocking boulders together, can mean moving debris.

➤ As the landslide nears, a slight rumbling sound that rises in amplitude is noticeable.

➤ Rapid rise in water levels of the creeks, likely followed by increased turbidity (soil content).

Early Warning System(EWS)

Philippine Institute of Volcanology and Seismology (PHILVOCS)

Philippine, Atmosphere, Geophysical and Astronomical Services Administration (PAGASA)

2.Sinkhole

•collapes of the surface layer of the ground

2 kinds of sinkhole

1NATURAL SINKHOLE

•caused by physical and chemical erosion.

2.MAN-MADE SINKHOLE

•caused by drilling, mining, road construction, and broken water or underground pipes.

Types of sinkhole

SULOTION SINKHOLE

➤ common in areas that have thin cover of soil on the surface of the ground which exposes the bedrock to water erosion.

➤ As the bedrock erodes, particles collect in the spaces it leaves and a small depression is formed over a period, eventually forming a hole.

➤ The bedrock may collapse suddenly, or it may happen over time.

2. Cover Subsidence Sinkholes ➤ occur when the bedrock is covered by soil and materials that are not well-knitted together. ➤ The soil in these areas are made mostly of clay or sand.

➤ Once the bedrock starts to erode, the clay or sand starts to enter through the cracks and settles into the spaces left behind, creating a cavity on the surface of the soil.

3. Cover Collapse Sinkholes

➤ occur when the bedrock is covered by a deep layer of soil and earth.

➤ A crack starts once the bedrock begins to get eroded. Weak points begin to form in the layers of soil above it.

The weak points eventually become a large hole within the bedrock that cannot support the weight above it.

The collapse occurs in an instant and can create large holes in a matter of minutes.

The impending signs of a sinkhole.

New cracks at the foundations of buildings and houses

Cracks in an area

☑ Depressions at ground level ☐ Rapid appearance of a crater in the ground

Geological Hazards OverviewGeological hazards are natural processes that can result in significant damage to life, property, and the environment. They can lead to:

• Injury and loss of life

• Property damage

• Loss of livelihood and services

• Social and economic disruption

• Environmental changes

Types of Geological Hazards

1. Landslides: Involves the downward movement of land.

   • Causes:

     • Geology: Soil or rock material composition

     • Morphology: Land structure

     • Human Activity: Agriculture, construction

   • Rainfall-Induced Landslides: Triggered by prolonged rainfall, increasing land mass weight; can occur rapidly with devastating effects.

   • Signs: Unusual noises, rumbling sounds, rapid creek water level rise.

   • Early Warning System: Includes organizations like PHILVOCS and PAGASA.

2. Sinkholes: Collapse of surface layers, caused by natural or man-made factors.

   • Types:

     • Natural Sinkholes: Result from erosion

     • Man-Made Sinkholes: Result from human activities (e.g., drilling, mining)

   • Types of Sinkholes:

     • Solution Sinkhole: Erosion of bedrock leading to depression.

     • Cover Subsidence Sinkholes: Erosion beneath soil layers creating cavities.

     • Cover Collapse Sinkholes: Rapid formation of large holes due to weakened support above.

   • Signs: New cracks, depressions, rapid ground cratering.