Geological Hazards and Natural Disasters

Study Notes

Natural Hazards

Sinkholes develop in areas with karst terrains, which have bedrocks made of limestone, dolomite, or gypsum that can be dissolved by groundwater over time.
Formation of sinkholes is often a result of the dissolution of these rocks, leading to the creation of underground spaces or caverns.
There are four types of sinkholes: dissolution, cover-subsidence, human-induced, and cover-collapse sinkholes.

Types of Sinkholes

Dissolution Sinkholes: form from the dissolution of limestone or dolomite by water or acid, often intensifying where water first contacts the rock surface or through pre-existing openings.
Cover-Subsidence Sinkholes: develop in areas where covering sediments are permeable, containing sand.
Human-Induced Sinkholes: associated with human activities like groundwater pumping, construction, and land development practices.
Cover-Collapse Sinkholes: occur where covering sediments contain a significant amount of clay, leading to abrupt development and potential catastrophic damages.

Landslides

Heavy rainfall can contribute to landslides in several ways: slope saturation, loosening of soil, and disturbance to terrain.
Signs of an impending landslide include:
- Physical changes: cracks or bulges on concrete or paved roads, sidewalks, and structures.
- Broken underground fixtures: indicating potential ground movement.
- Changes in land: sudden changes in the landscape, such as tilting trees or leaning utility poles.
- Unusual sounds: sounds like cracking or rumbling coming from the ground.
- Sediments in water: increased turbidity in nearby water bodies due to soil erosion.
- Slope movement: visible movement or slumping of soil or rocks on slopes.

Near-Earth Objects (NEOs)

NEOs pose various potential impacts on Earth, including:
- Direct Impact: NEOs like asteroids or comets colliding with Earth can cause significant damage, leading to loss of life, destruction of property, and environmental consequences.
- Climate Change: bolide impacts can result in climate change, sea level changes, tectonic activities, earthquakes, and increased volcanism, affecting global ecosystems and potentially leading to mass extinctions.
- Geological and Environmental Impacts: NEO impacts can affect geological, geophysical, and environmental systems.

Description

Learn about various natural hazards such as sinkholes, landslides, and coastal erosion, and the potential dangers posed by near-earth objects like asteroids and comets. Understand the importance of monitoring warning signs and mitigation efforts.