Geology and Disaster Risk Management
Geology and Disaster Risk Management
Mass wasting or mass movement refers to the downward movement of rock particles and soil down slopes due to gravity. Mass wasting is a key component of the erosional processes spectrum lying between weathering and transport by streams and glaciers where the loose particles are moved to deposition sites, including lake beds or the ocean basin. Mass movement processes occur continuously on types of slopes. Some mass movements happen very slowly while others occur suddenly, often resulting in disasters. Mass movements events are generally categorized by material and type of movement. The different types of mass movements include creep, slumps, slides, flows, and falls. In contrast, the factors that influence mass movements include the steepness of the slope, regional climatic conditions, slope material’s water content, and the amount of vegetation existing on the hill.
The different types of mass movements include creep, slumps, slides, flows, and falls. Creep involves soil movement and is often slow and gradual, with velocities ranging less than one centimeter per year. Creep manifests at the surface level through things such as tilted utility poles. Creeps are enhanced by wetting and drying rhythms and frost heaving, which washes the top fine particles. Slides involve rock masses or sediments and are characterized by sudden downhill movement. Slides are referred to as translational slides because they involve sudden movements along a specific direction ( HYPERLINK “https://www.researchgate.net/profile/A_Balasubramanian” Balasubramanian , 2011). A slump is a form of earthflow whereby a mass of regolith separates from the hillside following a spoon-shaped curved surface. Flows involve surface particles that assume a fluid-like behavior. Flows include earth flows, avalanches, debris flows, and mudflows. A rockfall can affect a rock mass or a single rock and occurs when the rock found on a steep slope dislodges and falls into the hill. The stones usually break along existing bedding planes or fractures.
The factors that influence mass movements include the steepness of the slope, slope material’s water content, and the amount of vegetation existing on the hill. The hill’s steepness influences mass movement because a steeper land surface results in a more significant gravity component, enhancing the downward movement of material. Slope material’s water content means that water in pores diminishes the strength of soils and rocks, increasing their susceptibility to movement (Core, n.d.). Vegetation influences mass movement because plants’ root systems bind together the grains of soil and regolith, thus preventing erosion. Regional climate affects mass movement due to precipitation and temperature. For instance, mass wasting is most likely to occur during springtime when water saturation, runoff, and snowmelt are most significant. Climate also influences the type of mass movement where the region with humid climates are prone to slides while those with water-saturated slopes experience a lot of falls.
In conclusion, the different mass movements include creep, slumps, slides, flows, and falls. In contrast, the factors that influence mass movements include the steepness of the slope, slope material’s water content, regional climatic conditions, and the amount of vegetation existing on the hill. Mass wasting is the downward movement of rock particles and soil down slopes due to the action of gravity. Mass wasting happens all the time and can either be slow or sudden. The different types of mass movements include creep, slumps, slides, flows, and falls. The factors that influence mass movements include the gradient of the slope, slope material’s water content, and the amount of vegetation existing on the slope.
Tsunamis refer to vast surges of ocean waves generated when an enormous volume of water is displaced. The displacement can result from volcanic eruptions, earthquakes, or various types of underwater explosions such as landslides, detonations, meteorite impacts, or glacier calving. Generally, anything that displaces a massive amount of water has the likelihood of generating a tsunami wave. Tsunamis are different from tidal waves because they do result from the moon’s gravitational pull. Tsunamis can start in any large water body, including oceans and inland seas. About 80% of tsunamis happen around the “ring of fire “- an area with a lot of geological activity in the Pacific Ocean where tectonic shifts cause earthquakes and volcanoes. A tsunami can reach heights of up to 30 meters which can cause a lot of destruction and damage to lives and property when they get ashore. Tsunamis generally originate from volcanic eruptions and earthquakes and are characterized by waves, wavelengths, velocity, frequency, and amplitude.
After a volcanic eruption or other activity that can generate an impulse occurs in a large body of water, a train of progressive oscillatory waves starts propagating over the water surface in ever-increasing circles. As the wavelengths grow, water reaches speeds of up to 800 kilometers per hour (Roy, 2014). This speed means that a powerful tsunami can cross the entire Pacific Ocean within 24 hours. While wavelengths can reach 200 kilometers, the wave height is significantly smaller, averaging a height of 60 centimeters. The long-wavelength enables them to conserve a lot of energy. Tsunamis are primarily shallow-water waves. They are different from conventional waves, which emanate from wind action upon the ocean’s surface. While regular waves have a period lasting to twenty seconds, tsunami periods can range from ten minutes to 120 minutes. The low height and steepness of tsunami give them total obscurity when moving in deep water, and ships cannot detect them.
On approaching coastlands, friction with the sea’s bottom decreases the wave’s velocity, which increases their height (amplitude), causing the coastal water to reach heights exceeding 30 meters. The wall of water develops as the fast-moving water at the surface piles up. The tsunami’s trough – the lowest point of the wave’s crest- typically reaches the shoreline first, during which it sucks the coastal waters seawards, exposing the sea flow and the harbor. The usual very low tide is often a vital warning sign of a pending tsunami as the crests of the waves laden with a vast volume of water usually hit the shore within ten minutes. A tsunami comprises a wave train made of a series of waves that can compound to form a destructive force as successive waves hit the shore. Like other water waves, a tsunami can be refracted and reflected by the sea floor’s topography and the coastline’s topography. Consequently, their effects vary from location to location. Overall, the main characteristics of tsunamis are waves, wavelengths, velocity, frequency, and amplitude.
In conclusion, tsunamis refer to ocean waves surges generated when a vast volume of water is displaced due to volcanic eruptions, earthquakes, or various types of underwater explosions such as landslides, detonations, meteorite impacts. Tsunamis can happen in any large water body, including oceans and inland seas. The main characteristics of tsunamis include waves, wavelengths, velocity, frequency, and amplitude.
Disaster Risk Reduction
Historically, tackling disasters often focused on developing an effective emergency response. However, at the turn of the 21st century, authorities increasingly acknowledged that disasters are not always natural. Managing and reducing the condition of hazard, vulnerability, and exposure could alleviate the effects of disasters. Therefore, because it is impossible to mitigate natural hazards’ severity, the best opportunity for mitigating risks was in reducing vulnerability and exposure. Disaster risk reduction is a component of sustainable development with far-reaching consequences and, therefore, requires a multi-sector approach encompassing the private sector, the government, and non-governmental organizations. Disaster risks are often thought to be an indicator of low development. Thus mitigating risk requires integrating disaster risk reduction policy into sustainable development objectives. Therefore, disaster risk reduction can be described as the systematic efforts of analyzing and managing the causes of disasters to reduce vulnerability and can be accomplished by implementing disaster risk reduction policies, identifying risk, utili
Geology and Disaster Risk Management