Geological Hazards PDF

## Geological Hazards **Lesson-6** **2nd Monthly** **Geological Hazard** - An adverse geologic condition capable of causing damage or loss of property or life. **1. Rainfall Induced Landslides** - Prediction of rainfall cover throughout the year can be an excellent determinant factor for rainfal...

## Geological Hazards **Lesson-6** **2nd Monthly** **Geological Hazard** - An adverse geologic condition capable of causing damage or loss of property or life. **1. Rainfall Induced Landslides** - Prediction of rainfall cover throughout the year can be an excellent determinant factor for rainfall-induced landslides. - Apart from the rain, there are two major geological factors that scientists consider: the slope and soil type. - Certain areas are prone to landslides due to tectonic factors. - In addition, rainfall here becomes a magnifier of the impact as it further weakens the soil. - Satellite mapping becomes extremely helpful. - These satellites enable vulnerable countries to see and evaluate the occurrences of landslides in their area, which can prove difficult when done manually on the ground. - Mountainous areas, as well as areas susceptible to rainfall, are prone to landslides. - This makes landslides a multi-factorial phenomenon. - This also means that nations that can gather data on their respective rainfall patterns, as well as the land composition, can potentially avoid the effects of rainfall-induced landslides. - Landslides usually occur due to: - Steep slopes. - Weakening of slope materials. - Weakening of rocks. - Overloading on the slope. - As one of the participating nations in global susceptibility, the country has its fair share of rainfall-induced landslides, with some of them being a result of human mismanagement. - Areas holding a certain degree of steepness may cause landslides when encountering heavy rainfall. - Rainfall weakens the slope's material contributing to the production of landslides. - Moreover, when rocks holding the slope together encounter weathering from the heavy rainfall, this can also induce landslides. - Landfills that people compile may also become weak when overloaded on a steep slope. - Couple this with rainfall, landslides become inevitable. - When a land falls, it is called a failure. - According to **PHIVOLCS (2018)**, there are various types of failure for every landslide. - This is true for both earthquake-induced landslides and rainfall-induced landslides. - Each type adheres to the 3 parts of a landslide as seen in Lesson 4. - Understanding the manner of its failure is just as important as understanding its causes. **Modes of Failure of Landslides** | Mode of Failure | Description | |---|---| | Falling | | | Toppling | | | Sliding | | | Spreading | | | Flowing | | *The mode of failure may vary depending on additional factors such as soil composition and the frequency of rainfall and typhoon occurrence in the area.* ## Mitigation Strategies to Prevent Loss of Lives and Properties - Maps have the capability of giving people foresight on the potential hazards in an area. - However, several communities have gone the extra mile to mitigate the possibility of a rainfall-induced landslide. - Even with the presence of signs, there is no definite time and area on a map where the landslide will happen; that is why monitoring systems near the affected areas are crucial. - It can be seen in the diagram that slope movement and rainfall are closely being monitored since these are factors involved in the hazard. - These efforts in mitigation can be classified under early warning system (EWS) that mitigate risks by sending signals to communities. - The following are some relevant insights on what to do before, during, and after a rainfall-induced landslide. ### A. Before - Avoid construction near steep slopes, mountain edges, drainage paths, or naturally prone erosion areas. - Assess the area using hazard maps. - Know the other pertinent details from the experts in the area. - See if there are measures you can take to fortify your location. - Know where water channels pass through. - Where water drains are where rainwater can pass through and affect land. - Know the basic emergency responses: traveling to the emergency evacuation site and preparing survival kits. - Craft a personalized emergency response plan for every member of the family. - Minimize the possibility of home-related hazards: strategize the area of gas, tubing for water, and electricity, among others. ### B. During - Stay alert and awake. - Be ready to constantly move away from the path of the landslide. - Be updated with the LGU through phone or other forms of media. - Leave your area only when it is safe. - Be aware of sounds that indicate moving debris such as: tree soils, boulders, and mud among others. - With the presence of water, these can move fast. - If you are located near a water channel, monitor the flow rate and muddy appearance of the water. - The increased rate of movement and turbidity of water are clear signs of an impending landslide. - If driving, be extra alert and extra careful with moving materials. ### After - Stay clear of the slide area as additional landslide may come. - Stay tuned with reliable media sources. - Be aware of the possibility of flooding. - Check for injured trapped individuals. - Forward them to first aiders and rescuers. - For structures seemingly unaffected, be sure to check for damage. - Ask for assessment from the experts. - Acquire data from what happened and consult on its prevention in your area. ## Underneath When Sinkholes Occur - Land subsides due to processes happening underneath. - The phenomenon goes deeper than fault line proximity or the occurrence of earthquakes. - What needs to be investigated is the geographic content of the land. - Once the foundation of the ground is weakened, any well-constructed structure can subside and incur damages. - According to the USGS (2018), a sinkhole is an area of ground that has no natural external surface drainage; hence, when water dissolves surface rock, a hole is formed. - Dissolution and suffusion are 2 processes that create 3 types of sinkholes. - There are times that sinkholes are a combination of these types. - The majority of the sinkholes originate from the dissolution. - To briefly explain, both water and carbon dioxide are present in the environment; thus their varying levels affect the generation of carbonic acid (weak acid) usually found in the mantle or cover sediment. - As the acid reaches the carbonate bedrock, this leads to dissolution, which will later translate into a collapse of the landmass above it. - Heavy rainfall and man-made activities are also some of the major factors that contribute to the exposure of the mantle to elements, which in turn reach through the carbonate later. - In addition, certain man-made activities such as mining can also inadvertently expose the bedrock, leading to a cascade of disasters above. **Suffusion:** - Is a phenomenon that exists whenever preexisting cavities underneath are covered or "overburdened" by sediments above. - Since there was no fortification of the carbonate bedrock below, sediments slowly erode over time going into the cavities. - Eroded carbonate bedrock starts small and increases in size over time until it completely sinks the landmass above. - Both cover-collapse sinkholes and gradual cover-subsidence sinkholes are caused by suffusion. - As presented in small crevices from limestone or dolomite-containing rocks, surfaces may be easily dissolved when frequently exposed to water. - The culprit here is the generation of carbonic acids as these acids act to dissolve the rocks. - Special attention must also be given to groundwater that is exposed to the atmosphere since carbon dioxide in the air serves as a reactant (together with water) to form carbonic acid. - This is also a factor in the creation of sinkholes. **If a sinkhole appears in your area, the following are some measures to take:** 1. Move away from the area. 2. Leave your affected house. Signs of damage may manifest; be sure to leave with important survival tools. 3. Mark the area to prevent anyone from falling into the sinkhole. 4. Communicate with experts for land assessment. Communicate with a nonlife insurance company to check if damages are covered. 5. Monitor the sinkhole for growth. Likewise, check nearby areas for other sinkholes. 6. Check the area for other damages. 7. Do not drop anything in the sinkhole. Sinkholes are connected to the groundwater. Any contaminant dissolves in groundwater may harm people accessing this water. ## Hydrometeorological Hazards **Lesson-7** **Typhoons** - Typhoons or tropical cyclones are given primary attention as they bring in most of the cascading hydrometeorological hazards. - Their formation and dynamics need understanding as this will be highly connected with the subsequent hazards. - As mentioned, typhoons originate mainly near the equator due to the presence of warm air and trade winds. - For a typhoon formation to occur, there should be a sufficiently large warm ocean with at least more than 27°C in temperature. - The warm body of water produces warm air that is lifted upward, producing a layer of atmosphere warmer than that of its surrounding counterparts. - From here on end, disturbances may be detected. - However, storms would only develop once the layer of atmosphere filled with warm air reach more than 5° of latitude from the equator. - From here on end, 2 theories stand that support its formation: - The Convective Theory - The Frontal Theory. **The Convective Theory** - It is posited that the mass of air becomes convectively unstable and moist compared to its surrounding air. - Following convection, this now brings the air upward. - Eventually, the air surrounding this area is drawn toward the low pressure area forming a cyclonic circulation. - Finally, Earth's rotation, centrifugal force, and the outward flow of air from the center at high levels contribute to further lowering the pressure. - Recall from news reports that the detection of LPA usually indicates an impending typhoon. **The Frontal Theory** - Many tropical cyclones form along the front b/w the trade winds and the equatorial air in the doldrums. **A typhoon has 4 life stages.** - ***Formative Stage***: This is the incipient stage when the tropical cyclone forms waves and the shear lines of pre-existing disturbances and winds usually remain below the typhoon force. - ***Immature Stage***: It is the depending stage of the cyclone during which it continues to deepen until the lowest central pressure and the maximum wind intensity are reached. - However, intensification does not usually take place since some have been known to die down even though the winds have attained typhoon force. - ***Mature Stages***: This is the stage of maturity of the tropical cyclones where the areas of circulations expand while the surface pressure no longer falls and no increase in maximum wind speed can be observed, which may last for a week. - ***Decaying Stage***: This is the dissipating stage of the tropical cyclone where the surface pressure rises and the area affected by the cyclones diminishes in size as it receives or dissipates due to friction and lack of moisture over continents or when colder and drier air enters through when they go poleward. **3 important motions for the formation of cyclones - circulation, convergence, divergence.** ## Heat Wave - Typically defined as a period of excessively hot weather. - Severe heatwaves can cause catastrophic crop failures, thousands of deaths from hyperthermia and widespread power outages due to increased air conditioning use. - The world meteorological organization recommends a definition of a heat wave when the daily maximum temperature exceeds the average maximum temp by 5°C (9°F) with the normal period being 1961-1992. **Negative effects on humans:** 1. Skin cancer 2. Heat stroke 3. Dehydration 4. Sunburn 5. Headache **The criteria for heat waves:** - Severe heatwave +5°C for regions where normal temp is above 40°C +7°C for regions less than 40°C. **Heat Wave:** - 3 to 4°C in the regions above 40°C. **Heat Cramps:** - Muscular pains and cramps due to heavy exertion. **Heat Exhaustion:** - It typically occurs when people exercise heavily or work in a hot humid place where body fluids are lost through heavy sweating. **Heat Stroke:** - It is a life-threatening condition. - The victim's temperature control system, which produces sweating to cool the body, stops working. - The body temp will be very high, can damage your brain, and cause death. **Preparation:** - Install window air conditioners. - Check air conditioning ducts for proper insulation. - Use temporary window reflectors ex: aluminium foil-covered reflectors. - Weather strip doors. - Cover your windows that receive morning or afternoon sun with drapes/shades. **SAFETY: Do's and Don't's** **Before:** Everything in preparation + - Listen to local weather forecast and make yourself aware of upcoming temp changes. - Know those on your neighborhood who are elderly, young and sick or overweight. - They are more likely to become victims of excessive heat and may need help. - Get trained in first aid to learn how to treat heat-related emergencies. **During Heatwaves:** - Never leave your children or pets alone in closed vehicles. - Stay indoors as much as possible and limit exposure to the sun. - Stay on the lowest floor out of the sunshine. - Eat well-balanced, light and regular meals. - Drink plenty of water even if you don't feel thirsty. - Protect face and head by hat or a cloth. ## Cold Wave - A cold wave is a weather phenomenon that is distinguished by a cooling of the air. - A cold wave is a rapid fall in temperature within a 24-hour period. **Criteria for cold wave:** - Severe cold wave: -5°C deviation from normal for regions where normal temperature is less than 10°C. - Cold Wave: Departure of minimum temperature by -3°C to -4°C from normal, where normal minimum temperature is less than 10°C. **Impact of cold wave:** - Extreme winter cold often cause poorly insulated water pipelines and mains to freeze. - Demands for electrical power and fuel costs rise dramatically during such times. - Fires, paradoxically, become even more of a hazard during extreme cold. **Counter Measures:** - Most people can dress appropriately and can even layer their clothing should they need to go outside or should their heating fail. **Safety Tips** **Do's and Don't's** **Before and During**