How do volcanic hazards differ between continental and oceanic settings?

Volcanic hazards in continental settings often involve explosive eruptions, while oceanic settings typically see effusive eruptions.

In continental settings, volcanoes are often associated with explosive eruptions. This is primarily due to the type of magma involved. Continental volcanoes are typically fuelled by felsic or intermediate magma, which has a high silica content. This high silica content makes the magma highly viscous, preventing gas from escaping easily. As a result, pressure builds up within the volcano until it is released in a violent explosion. These explosive eruptions can produce a range of hazards, including pyroclastic flows, ash fall, and lahars. Pyroclastic flows are fast-moving currents of hot gas and volcanic matter that can destroy everything in their path. Ash fall can bury landscapes, damage buildings, and pose a health risk to humans and animals. Lahars are mudflows caused when volcanic ash and debris mix with water, either from melting snow or heavy rain.

On the other hand, volcanoes in oceanic settings are typically associated with effusive eruptions. These eruptions are characterised by the steady flow of mafic lava, which has a low silica content. This low silica content makes the lava less viscous, allowing gas to escape easily and preventing the build-up of pressure that leads to explosive eruptions. Instead, the lava flows steadily out of the volcano, creating hazards such as lava flows and volcanic gases. Lava flows can cause damage by burning and burying everything in their path, but they typically move slowly enough that people can evacuate in time. Volcanic gases, which can include water vapour, carbon dioxide, and sulphur dioxide, can pose a health risk and contribute to climate change.

In addition, the location of these volcanoes can influence the type of hazards they produce. Continental volcanoes are often located near populated areas, increasing the risk to human life and property. Oceanic volcanoes, meanwhile, are often located underwater or on small islands, limiting their potential to cause human casualties but potentially triggering tsunamis.

Overall, while both continental and oceanic volcanoes can pose significant hazards, the nature of these hazards can vary greatly depending on the type of magma involved and the location of the volcano.