DRRR_Q4_ACTIVITY_LESSON4_OTHER-GEOHAZARDS-LANDSLIDE-SINKHOLE

Geologic conditions beyond earthquakes and volcanic eruptions can pose hazards to lives and properties.
Important hazards discussed:
- Landslides
- Sinkholes
These hazards arise from the topographical and geologic makeup of land.

A landslide, or "landslip," involves ground movement on sloping terrain.
Landslides do not occur on flat grounds; gravity pulls land downward, especially when saturated by rain.

Prolonged or heavy rainfall can saturate topsoil and bedrock, weakening support for structures.
Areas with steep slopes, dense populations, and denuded land are highly susceptible.
Vegetation loss means less root structure to stabilize soil, increasing the chance of landslides, mudslides, or mudflows.

Soil Creep
- Very slow movement, hard to detect, minimal damage.
Slumping
- Faster movement; land slips more noticeably.
Debris Flow
- Happens when the slope is saturated with water causing a mass of rock and soil to slide down.
Rock Fall
- Sudden landslides triggered by heavy rain, where rocks loosen and fall.

Landslides can be both natural and human-induced, sharing common driving forces of gravity and slope failure.

Climate
- Changes in rainfall greatly impact soil stability; excessive saturation can lead to landslides.
Earthquakes
- Seismic activity causes soil shifts, leading to potential landslides, especially on steep slopes.
Weathering
- Deterioration of rock due to natural processes weakens the material, leading to landslides.
Erosion
- Erosion by water, wind, and ice undermines slope stability, facilitating landslides.
Volcanoes
- Eruptions can trigger landslides, particularly when wet conditions are present.
Forest Fires
- Lead to soil erosion and increased risk of landslides.
Gravity
- Steeper slopes experience greater gravitational pull, leading to landslides.

Mining
- Blasting and vibrations weaken surrounding soil stability.
Clear Cutting
- Eliminates trees that stabilize soil, increasing vulnerability to landslides.

Sinkholes resemble sudden holes that open in the ground, appearing like giant pits.

Sinkholes are depressions formed due to the collapse of surface layers, commonly in areas with limestone or soft minerals.
They can lead to significant structural damage and vary in depth.

Frequent rainfall can weaken the ground and create cavities leading to collapses.
Human activities, including groundwater pumping and construction, alter the natural drainage and can trigger sinkholes.

Solution Sinkholes
- Form in areas with limestone and are caused by water dissolving rock.
Cover-collapse Sinkholes
- Develop rapidly and can cause significant damage, generally in clay-rich sediments.
Cover-subsidence Sinkholes
- Form gradually where sediments are permeable and consist mainly of sand.
Artificial Sinkholes
- Created by human activities such as mining and changes in groundwater levels.

Water dissolves minerals in rocks, creating voids; lowering water levels can remove support from surrounding soil leading to collapse.

For Landslides:
- Bulging ground, water seepage, tilted structures, cracked surfaces, leaky water pipes.
For Sinkholes:
- Leaning signposts, new ponds or puddles, groundwater clouds or changes in quality.

Instruments like the Abney level and laser rangefinder measure slope angle and soil strength.

Ground-penetrating radar (GPR) detects subsurface changes and voids, aiding in assessing potential sinkholes.