Earthquake and Volcanic Hazards

Flashcards Check Knowledge Test Yourself

Edexcel iGCSE > Hazardous Environments > Earthquake and Volcanic Hazards

Earthquake and Volcanic Hazards

Volcanic Hazards

Volcanic hazards are primarily found at constructive and destructive plate boundaries and near hot spots but not at conservative plate margins or collision zones. The fundamental cause of these hazards is the expulsion of magma from beneath the Earth’s crust to the surface. The type of eruption differs by location: at constructive margins, where magma rises, the lava is typically hotter and more fluid, resulting in less violent eruptions. Conversely, at destructive margins, the more acidic and viscous lava tends to create more violent eruptions, including pyroclastic flows and lava flows, potentially contributing to acid rain and climate alteration due to the greater volume of material released into the atmosphere. Lahars, or volcanic mudflows, can form when volcanic ash combines with water. Though relatively slow-moving, hot spot lava flows, such as those in Hawaii, can still incinerate structures and vegetation. It’s important to note that volcanic hazards become a concern when they threaten human populations. The severity of the impact from primary and secondary volcanic hazards is contingent upon the eruption’s magnitude and the proximity of populations at risk.

Primary Hazard
Lava flow
Ash
Pyroclastic flows
Gass emissions

Secondary Hazard
Lahars (volcanic mudflows)
Acidification
Landslides
Climate change (cooling)
Fire

Earthquake Hazards

Earthquakes frequently happen along the boundaries where tectonic plates meet. As these plates shift in diverse directions, stress accumulates. When this stress is suddenly released, it causes the ground to shake—an event known as an earthquake. Additionally, certain earthquakes can be induced by human actions, including mining operations, the construction of substantial dams, and the underground detonation of explosives.

Primary Hazard
Ground shaking
Liquefaction

Secondary Hazard
Gas leaks
Fires
Landslides
Debris flow and mudflow
Tsunamis

Summary

Volcanoes ccur at constructive and destructive plate margins and hot spots, not conservative margins or collision zones, with eruptions varying from less violent, fluid lava to more violent, viscous flows that can cause climate effects and acid rain.
Primary volcanic hazards include lava flow, ash, pyroclastic flows, and gas emissions, with secondary hazards like lahars, acidification, landslides, climate cooling, and fires posing risks to nearby human populations.
Earthquakes occur at tectonic plate boundaries due to the release of built-up pressure, leading to ground shaking, with human activities like mining, dam construction, and bomb testing also capable of triggering quakes.
Primary earthquake hazards include ground shaking and liquefaction, with secondary hazards including gas leaks, fires, landslides, debris flow, mudflow, and tsunamis, dependent on the earthquake’s magnitude and the affected population’s location.