Copy-of-W7-Geologic-Processes-and-Hazards.pptx

Geologic Processes and Hazards  you are expected to: 1. describe the various hazards that may happen in the event of earthquakes, volcanic eruptions, and landslides (S11/12ES-Ia-e-30); 2. using hazard maps, identify areas prone to hazards brought about by earthquakes, volcanic erup...

Geologic Processes and Hazards  you are expected to: 1. describe the various hazards that may happen in the event of earthquakes, volcanic eruptions, and landslides (S11/12ES-Ia-e-30); 2. using hazard maps, identify areas prone to hazards brought about by earthquakes, volcanic eruptions, and landslides (S11/12ES-Ia-e-31); and 3. identify human activities that speed up or trigger landslides (S11/12ES-Ia-e-33)  Complete each sentence and write the letter of your answer on a separate sheet. 1._____are water waves generated by earthquakes, undersea volcanic eruptions, or landslides that hit bodies of water. A.Tsunamis B. Tidal waves B.C. Wind waves D. Wind surges 2. __________ is the disruptive up, down, and sideways vibration caused by passing seismic waves through the ground. C. Folding B. Ground shaking C. Ground rupture D. Ground subsidence  3. _____________ is the deformation on the ground that marks the intersection of the fault with the earth’s surface. A.Faulting B. Landslide C. Liquefaction D. Ground rupture 4. _______ is a phenomenon that occurs when loosely packed, water-logged sediments near the ground surface lose their strength in response to strong ground shaking. B.Liquefaction B. Sedimentation C. C. Stratification D. Weathering 5. Earthquake-induced landslide is the down slope movement of rocks, soil, and other debris commonly triggered by intense _____________. A. irrigation B. mining C. rain D. shaking  EARTHQUAKE HAZARDS The Philippine Institute of Volcanology and Seismology (PHIVOLCS) is a service institute of the Department of Science and Technology (DOST) that is principally mandated to mitigate disasters that may arise from volcanic eruptions, earthquakes, tsunamis, and other related geotectonic phenomena. The next activity is about earthquake information released by PHIVOLCS and it will require you to recall some of the terms used to describe an earthquake.  Types of Earthquakes There are two types of earthquakes: tectonic and volcanic earthquakes. This lesson will discuss tectonic earthquakes. Tectonic earthquakes are produced by sudden movement along faults and plate boundaries. (Bagtasa et al. 2016, 219–30) For tectonic earthquakes, the focus is the point inside the earth where the earthquake started, also called the hypocenter. The point on the surface of the earth directly above the focus is called the epicenter.  Measuring the Strength of an Earthquake There are two ways of measuring the strength of an earthquake which are magnitude and intensity.  Magnitude is proportional to the energy released by an earthquake at the focus. It is calculated from earthquakes recorded by an instrument called seismograph. It is represented by Arabic Numbers (e.g. 4.8, 9.0).  Ground Shaking and Location How seismic waves shake the ground during an earthquake depends on the geologic layering. Figure 3 shows how an earthquake wave going through solid bedrock has high frequency and low amplitude. When the waves go through weaker material, they oscillate with higher amplitude but lower frequency.  Earthquake Hazards Hazards are events or phenomena that may cause loss of life, injury or other health impacts, property damage, loss of livelihood and services, social and economic disruption, or environmental damage. The most common earthquake-related hazards are ground shaking, ground rupture, liquefaction, earthquake-induced landslides, and tsunami.  HAZARD MAPS Hazard Maps are maps that show different hazards that may affect a certain area. Several types of hazard maps related to earthquakes are available. A ground shaking hazard map shows the distribution of earthquake shaking levels that have a certain probability of occurring. A ground rupture hazard map shows areas wherein faults cut across. There are also hazard maps for liquefaction, earthquake-induced landslide, and tsunami. VOLCANIC HAZARDS  TAAL VOLCANO BALLISTIC PROJECTILES HAZARD MAP LANDSLIDES  CAUSES OR TRIGGERING MECHANISMS The primary driving factor of landslides is gravity acting on a portion of a slope that is out of equilibrium. There are two primary categories of causes of landslides: natural and human-caused. Sometimes, landslides are caused, or made worse, by a combination of the two factors. The following are some of the major landslide triggering mechanisms.  Volcanic Activity The cone-shaped structures of volcanoes are young, unconsolidated, and geologically weak structures that in many cases can collapse and cause rockslides, landslides, and debris avalanches. Many islands of volcanic origin experience periodic collapses of their edges due to the weak volcanic surface deposits. Such collapses may create massive submarine landslides that may also rapidly displace water, subsequently creating deadly tsunamis. (Highland and Bobrowsky 2008)  AREAS GENERALLY PRONE TO LANDSLIDES Landslides can accompany heavy rains or follow droughts, earthquakes, or volcanic eruptions. Places most vulnerable to landslides include: areas where fires or human modification of the land have destroyed vegetation; areas where landslides have occurred before; steep slopes and areas at the bottom of slopes; slopes that have been altered for construction of buildings and roads; waterways along streams or rivers; and areas where land is heavily saturated with water. (CDC 2019)  GEOHAZARD MAPS According to PHIVOLCS, the Philippines is prone to typhoons and earthquakes, thus, occurrence of landslides is inevitable. Awareness and preparedness are the most effective prevention and mitigation measures against possible threats of landslide in the community. The Mines and Geosciences Bureau issues geohazard maps that illustrate landslide and flood susceptibility.