GEOL 3400 Geologic Hazards Natural Hazards Geologic Ground

GEOL 3400: Geologic Hazards Natural Hazards: Geologic Ground Deformation

Natural Hazards: Geologic An Introduction GEOL 3400: Geologic Hazards • slope failure – three variations • falls: involves free fall in air • slides: sliding of coherent mass on basal failure surface • flows: mass moves as viscous fluid consisting of air, sediment, and water • surface failure – two variations • collapse: rapid vertical downward movement of Earth’s surface • subsidence: slow sinking of Earth’s surface 30 -Aug-21 2

Natural Hazards: Geologic GEOL 3400: Geologic Hazards An Introduction failure, the downslope movement of a mass on a sloping • slope failure surface, e. g. hillside, cliff, mountain side, hill, peak, mound, hummock, etc. , under the influence of gravity – three variations: • falls: involves free fall in air • slides: sliding of coherent mass on basal failure surface • flows: mass moves as viscous fluid consisting of air, sediment, and water – involves both vertical and horizontal components of motion – a mass movement commonly involves multiple of types of failure as it evolves • for example, fall can change to flow, or slide and then flow – never goes other way – these can be rapid (catastrophic) or slow (chronic) onset hazards 30 -Aug-21 3

Natural Hazards: Geologic GEOL 3400: Geologic Hazards An Introduction failure, sinking of horizontal or level Earth surface under the • surface failure influence of gravity – two variations: • collapse: • subsidence: sudden sinking or gradual downward settling of the ground surface with little or no horizontal motion – involves predominantly vertical motion – vary in nature and risk: • collapse: rapid (catastrophic) onset hazards • subsidence: slow (chronic) onset hazards – mostly local in spatial scope 30 -Aug-21 4

Natural Hazards: Geologic GEOL 3400: Geologic Hazards Summary 30 -Aug-21 5