Solid Earth

Sudden slip on a fault releasing seismic waves that shake the ground and damage structures and lifelines.

Also: ground shaking, quake

Shaking triggered by human activity, such as reservoir filling, fluid injection, mining or extraction, that changes stress on a fault.

Also: human-triggered earthquake

A cluster of smaller shocks after a large earthquake that can damage weakened structures and endanger rescue work.

Ground displacement along the trace where a fault breaks the surface, cutting roads, pipelines and buildings built across it.

Loose, water-saturated soil losing strength under shaking and flowing like a liquid, tilting or sinking what stands on it.

Open cracks in the ground, from shaking, subsidence, drying or land movement, that damage foundations and buried pipes.

A cluster of many earthquakes without a clear main shock, often linked to fluids or magma, that damages buildings cumulatively and may precede an eruption.

Also: seismic swarm

Rising earthquakes, ground swelling or gas release at a volcano that may or may not end in an eruption.

Molten rock moving over the ground and burying or burning what it reaches, slowly enough that people can usually move away.

Also: lava dome

Fine volcanic fragments settling from an ash cloud, loading roofs, clogging engines and filters and burying crops.

Also: tephra fall

Airborne ash from an eruption that damages jet engines and closes airspace over large distances.

Also: aviation ash

Rocks and blocks thrown from a vent on ballistic paths that strike people and structures near the crater.

Also: volcanic bombs

A fast, hot avalanche of gas, ash and rock racing down a volcano's flanks and destroying everything in its path.

Also: pyroclastic density current, nuee ardente

A fast slurry of volcanic debris and water that surges down river valleys, during an eruption or long after it.

Also: volcanic mudflow

Sulphur dioxide, carbon dioxide and fine aerosols released by a volcano that poison people and animals, acidify water and haze the air.

Also: vog, sulphur dioxide plume

A large part of a volcanic edifice failing and sliding away, sometimes uncorking an eruption or generating a tsunami.

A sudden steam-driven blast when groundwater is flash-heated beneath a volcano or geothermal field, throwing rock and gas with almost no warning.

Also: steam explosion, hydrothermal eruption

Sudden release of dissolved carbon dioxide from a deep crater lake whose dense gas cloud flows downhill and suffocates people and animals.

Also: lake overturn gas burst, carbon dioxide lake eruption

Extrusion of pressurised mud, water and gas from depth that buries land and settlements and can burn when methane ignites.

Also: mud eruption

Blocks detaching from a steep face and falling, bouncing or rolling onto whatever lies below.

Forward rotation and overturning of a rock or soil mass about a pivot at its base.

A mass of soil or rock moving downslope along a defined shear surface, from slow creep to sudden failure.

Also: landslide, rockslide

Gently sloping or flat ground breaking into blocks that move sideways, usually over a weak or liquefied layer.

A fast, water-charged mass of mud, rock and wood surging down a channel, often after intense rain or on burnt slopes.

Also: mudslide

Slow to rapid flow of wet fine-grained soil down a slope, deforming the ground and burying what lies on it.

A very large, rapid mass of fragmented rock that travels far beyond the foot of its slope.

Also: sturzstrom

Slope failure on the sea floor that breaks cables and pipelines and can generate tsunamis.

Very slow downslope movement of soil and rock that gradually distorts roads, walls and pipelines.

Gradual sinking of the ground, often from groundwater, oil or gas withdrawal, mining or peat drainage, that floods and cracks cities.

Also: ground sinking

Rise of the ground from tectonic or magmatic movement that changes shorelines, river courses and harbour depths.

Sudden collapse of the ground into a cavity formed by dissolving rock, old workings or leaking pipes.

Also: cave-in

Clay soils that swell when wet and shrink when dry, lifting and cracking foundations, roads and pipes.

Also: expansive clay

Compression of soft or loose ground under load or drainage, so that buildings and embankments settle unevenly.

Also: compressible soil

Methane, radon or carbon dioxide seeping from the ground into buildings and workings, where it can explode or poison.

Also: radon, methane seepage

Sinking or sudden collapse of ground above active or abandoned mines that cracks buildings, pipes and roads and can open pits at the surface.

Also: mine collapse subsidence, crown hole

Loss of topsoil to water or wind, stripping fertility and filling reservoirs and channels downstream.

Cutting of river banks and shifting of channels that undermines land, roads, levees and homes.

Also: channel migration

Retreat of the shoreline and cliffs under waves, currents and storms, removing land and exposing buildings.

Also: shoreline retreat, cliff retreat

Moving sand burying farmland, roads and settlements at the margins of deserts and coasts.

Also: sand drift

Sediment filling reservoirs, harbours and channels, cutting storage, flow capacity and navigation depth.

Also: sedimentation

A river abruptly abandoning its channel for a new course across its floodplain or fan, flooding settlements far from the old channel.

Also: channel switching, river course change

Loss of the river sediment that sustains deltas, through dams and sand mining, so that deltas sink and erode relative to the rising sea.

Also: sinking delta, delta drowning

A fast underwater avalanche of sediment-laden water down submarine slopes and canyons that can break seabed cables and pipelines over hundreds of kilometres.

Also: submarine sediment flow, canyon flushing

An eruption on or below the sea floor that can explode at the surface, raise floating pumice rafts, cut cables and generate local tsunamis.

Also: undersea eruption, surtseyan eruption

Sudden escape of trapped gas through seabed sediments that can destabilise foundations, sink vessels through lowered buoyancy and release methane.

Also: shallow gas blowout, pockmark eruption, seabed methane seep

A large mat of floating volcanic pumice drifting from an eruption that blocks ship intakes, closes harbours and smothers coasts.

Also: floating pumice

Removal of seabed nodules, crusts or vent deposits and the sediment plumes it raises, destroying slow-recovering deep-sea habitats over wide areas.

Also: seabed mining plume, nodule mining damage