Geohazards (earthquakes, volcanoes, and landslides)

Geohazards

Geohazards refer to geological and environmental conditions that have the potential to cause widespread damage or harm.
They are naturally occurring processes and can include earthquakes, volcanoes, and landslides.
These processes are linked with the dynamic nature of Earth’s tectonic activities and are often unpredictable.

Earthquakes are caused by a sudden release of energy in the Earth’s crust that creates seismic waves.
The location of the earthquake initiation beneath the Earth’s surface is called the focus, while the point of the surface directly above it is known as the epicentre.
The energy released travels in seismic waves that result in ground shaking and other associated phenomena.
The strength of an earthquake is measured by its magnitude, while the perceived shaking and damage is assessed by its intensity.
Earthquakes are mostly associated with tectonic activity, specifically along plate boundaries.

Volcanoes are geological features that form around a vent or fissure in the Earth’s crust through which magma, gases, and volcanic ash are ejected.
They are generally found on tectonic plate boundaries, particularly convergent and divergent boundaries.
The two primary types of volcanoes are shield volcanoes, with gentle slopes produced by fluid basaltic lavas, and stratovolcanoes, with steep slopes resulting from viscous andesitic to rhyolitic lavas.
Volcanic eruptions are categorised into effusive eruptions, where lava steadily flows out of a volcano onto the ground, and explosive eruptions, where major explosions of gas and rock fragments occur.
Volcanoes pose numerous hazards including lava flows, pyroclastic flows, ash falls, gas emissions, and lahars (mudflows).

Landslides refer to the movement of rock, earth, and debris down a slope due to gravity.
They are triggered by factors that destabilise the slope such as heavy rainfall, earthquakes, volcanic activity, human activity or the undercutting of cliffs by rivers or wave action.
Types of landslides include rockfalls, slides, flows, topples, and creeps.
They can cause severe damage to infrastructure, property and loss of lives.
Understanding and mapping landslides can allow for better hazard mitigation through effective land use planning and engineering solutions.

Mapping and monitoring geohazards can help predict the future occurrences and potential areas of risk.
Evacuation plans and early warning systems can be implemented to reduce the risk posed by such geohazards.
Infrastructure can be designed or modified to withstand seismic activities and reduce damages from eruptions and landslides.
Public education and awareness are critical elements in mitigating the impacts of geohazards.
Long term land-use planning based on geohazard potential can be an effective risk reduction strategy.