DRRR Lesson 2 & 3: Geologic Hazards & Sinkholes PDF

**DRRR LESSON 2** **Causes of Geologic Hazards** **NATURAL CAUSES OF LANDSLIDES** - - Climate - Earthquake - Weathering - Erosion - Volcanic Eruption - Forest Fires - Gravity **CLIMATE** - Long-term climatic changes can significantly impact soil stability - A general...

**DRRR LESSON 2** **Causes of Geologic Hazards** **NATURAL CAUSES OF LANDSLIDES** - - Climate - Earthquake - Weathering - Erosion - Volcanic Eruption - Forest Fires - Gravity **CLIMATE** - Long-term climatic changes can significantly impact soil stability - A general reduction in precipitation - When sloped areas are completely saturated with water, landslides can occur. - If there is absence of mechanical root support, the soils start to run off **Earthquakes** - - **Weathering** - - - **Erosion** - **Volcanic eruption** - - - **Forest fires** - - - **Gravity** - - **HUMAN CAUSES OF LANDSLIDES** - Mining - Clear cutting **Mining** - Mining activities that utilize blasting techniques contribute mightily to landslides. - Vibrations emanating from the blasts can weaken. - Earthwork alters the shape of a slope, imposing new loads on an existing slope **Clear cutting** - technique of timber harvesting that eliminates all old trees from the area. - decimates the existing mechanical root structure of the area. **Rainfall-Induced landslides** - - - - **NATURAL CAUSES OF SINKHOLE -- Dissolution of sedimentary rocks** - - - - - - - **SIGNS OF IMPENDING LANDSLIDE** - **Earlier landslide as indicator** - If there's frequent occurrence of landslides in a section - Multiple landslide events within the same place - A reactivated landslide - Inspecting an area of an old landslide for scarps and deposits **2. Tension cracks** - These are caused by the stress and friction produced by geologic materials - Tension cracks above an existing landslide can hint at a future reactivation. - These cracks are located on higher elevated ground. - Cracks that are found on flat terrain are caused by fault movement and not landslide indicators. **3. Things Moving** - Deformation and movement of non-living objects not caused by human - trees are bending up in a J-curve as a sign that the ground slips out from underneath them. - A patch of angled forest on a slope or J-curved trees somewhere can be a good indicator that the ground is less solid than it seems. - no longer closing properly, or broken utilities. - This motion can be slow or rapid. Rapid landslides are results of sudden collapse of a slope. This happens in terrains that are steeper - Creaking and cracking can also be warning signs **4. Water Doing Something Different** - Changes in water flow. - Springs, seep, or wet ground may appear on a seemingly dry terrain. - Similarly, unexpected withdrawal of water also indicates the same. - Water causes alteration of the pressure within the slopes of a terrain. - A debris flow is a very wet, very mobile landslide, where water is loaded with trees, mud, rock, and everything else caught in the current. **WARNING SIGNS OF AN IMPENDING SINKHOLE** - Trees or fence posts that tilt or fall - Foundations that slant - New small ponds that appear after rain - Cracks in the ground - Sudden drainage of a pond - Rapid appearance of a hole in the ground - Dips, depressions, slopes that appear in a yard - Dead patches of grass or plants - Sinkholes in the neighborhood - Wilted vegetation in a limited area - Well water that is discolored or contaminated with debris - Cracking or buckling of home's concrete slab - Presence of odd bugs like slugs, centipedes in homes - Earthly odor in home after rain - New or widening cracks - Separation between walls and ceiling or floors - Uneven floors, warping of hardwood, bulging or sagging sections - Doors or windows that don't open or close easily - Cracks in sheetrock near doors or window