2.1 Factor of Submarine Landslide
Landslide is a phenomenon that happens on both land and underwater. This mass movement down the slope may due to the slope overstepening, increase in loading on the slope, increase in pore water pressure and etc. Landslides happens when the soil was failed due to shear stress exceed the shear strength of soil. According to Zydron and Zawisza (2011) the stability of slope depending on mechanical characteristic of soil which is the angle of internal friction and cohesion of soil. Submarine landslide failure have the same mechanism as landslide on land.
Sediments that deposited continental slope one of factor that can cause submarine landslide. This sediments were carried from land by rivers to continental shelf
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When these two factors contributed in submarine landslide, the resisting force will be sunken by downward forces and shear strength not able to withstand it, the slope will be shifted downward to planar surfaces.
There are a lot of factors that triggered submarine landslide. According to Masson, Harbitz, Wynn, Pederssen and Lovholt (2006) major factor influencing submarine landslide are elevated pore water pressure that reduce the frictional resistance toward sliding and also a weak soil at the below of soil layer that fail to hold itself. Elevated pore water pressure can be resulted from normal depositional process which sediments are carried from land to continental shelf to continental slope by erosion, ocean current, or storm and also from transient process like earthquake.
2.2 Impact of Submarine
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Submarine landslide induced by submarine earthquakes are the principal cause of large tsunamis and earthquakes also play indirect role (Lovholt et al. 2005). Wave’s energy produced by earthquakes will be decreasing as it far away from the point sources because the radial damping (distal effect). If the tsunami generated by two dimension sources of earthquakes it will reduces the radial spreading. Tsunami character must be identified in order to study the tsunami genic potential. The main element that need to be known are landslide volume, initial acceleration, velocity, thickness of landslide and also the length. Lovholt et al. (2005) stated that there is a reasonable correlation between landslide volumes and landslide dynamics parameters.
Besides, the impact of tsunami generated by submarine landslide can be seen in 1996 Finneidjord slide, in Northern Norway. In this event, four people were killed with only 0.001km3 was
An increase in pebble roundness in the direction of long shore drift. The process of attrition will erode the pebbles. c) A decrease of pebble size in the direction of long shore drift, again attrition is involved. d) Undercutting (active erosion of the cliffs at one end of the bay).
Longshore drift influences the deposition and erosion of sediments. Waves erode the coast and transport the eroded material along the coastline. Over a period of time, the material will be deposited on a beach or form a larger feature such as a spit. Groynes are structures built at equal intervals along the coastline. Their purpose is to restrict longshore drift, preventing coastal erosion.
There are three clear landslides; the southwest landslide is stream-laid sand and gravel from the quaternary that was located on a steep slope resulting in gravity pulling sediments down the steep slope. The northeast landslide appears to be tuff sediments that have fallen upon biotite-quartz diorite rocks. The northwestern landslide is the largest of the landslides. The landslide occurred just south of the creek; erosion must have lowered the creeks elevation creating a steep decline resulting in Bena gravel to fall.
Tsunamis can go the same speed as a jetliner and that massive wave can out run the fastest runner. When there is a lot of waves at once, or the water goes back that is a sign that a tsunami is coming. If that tsunami is far then people need to get to the tallest and strongest building there is in the city that way they are safe and helicopter can pick them up. Tsunamis can wipe out an entire city or 1/4 of the country. Tsunamis can last up to an hour, or more.
Primary coasts are divided into two categories: submergent and emergent coasts. Submergent coastlines result from a general sea-level rise and crustal subsidence. Most of the eastern United States has submergent coastlines. One example is the Chesapeake Bay. Emergent coastlines result from the land being lifted, either by tectonic activity or rebound from the weight of heavy glaciers, which exposes the former sea bottom bit by bit forming continuously new shoreline.
is being eroded by the sea so that cliffs, up to 20 metres high rise
Additionally, this earthquake occurred on a thrust fault. This fault was a subduction zone slip which occurred primarily beneath the ocean were the Pacific plate plunges underneath the North American plate. This sudden upward movement of the sea floor along the rupturing fault generated a massive tsunami. This vertical deformation
The Tohoku earthquake caused by the movement of the Pacific plate slides underneath the Eurasia plate at the rate of three inches per year, associated with Japan Trench
Living in Bangladesh, we have seen quite disastrous mudslides from the past few years. Mudslide is also called a landslide or a land slip. It is a downward mass movement of earth or rock on unstable slopes, including many forms resulting from differences in rock structure, coherence of material involved, degree of slope, amount of included water, extent of natural or artificial undercutting at the base of the slope, relative rate of movement, and relative quantity of material involved. There are numerous facts that can cause a mudslide and there are also numerous effects that it can cause us.
Hydraulic Action, when waves hit the cliff, air is forced into cracks, and then as the wave retreats this air expands explosively. Over time the cracks enlarge, weakening the base of the cliff causing erosion.
... although we may never be able to understand exactly what soil failures can occur when a natural disasters take place, as time goes on and testing instruments and materials advance we will hopefully have a better understanding of what we can do to avoid soil failures and come up with a better and more sufficient method of improving the soils structure and strength permanently. While researching the information for this report I feel I have a much better understanding for construction geo-technics and foundations especially regarding the deformation, liquefaction and pile information related to this specific event. I hope to carry the information I have learned from this event into the construction field and apply them towards an authentic project that’s taking place and know that the information, regarding soils, I have given input on will be precise and accurate.
Diastrophism is deformation of earth’s crust, caused by folding and faulting. Convergent plate boundaries are formed through diastrophism. A convergent boundary (or a destructive plate boundary) is formed when two or more tectonic, lithospheric plates collide. There are two types of plates: oceanic (more dense) and continental (less dense). If two oceanic plates collide, subduction will occur. Subduction refers to the movement of one plate, sliding underneath another plate. The plate that is pushed down is consumed by the magma in the internal structure of the earth. When this happens, there will be a large, deep underwater trench where the subduction occurred (Mariana’s trench is an example of this). The plate that is consumed by magma causes
U.S. Geological Survey. Worldwide Overview of Large Landslides of the 20th and 21st Centuries. 6 December 2010. 3 February 2011 .
Earthquakes belong to the class of most disastrous natural hazards. They result in unexpected and tremendous earth movements. These movements results from dissemination of an enormous amount of intense energy in form of seismic waves which are detected by use of seismograms. The impact of earthquakes leaves behind several landmarks including: destruction of property, extensive disruption of services like sewer and water lines, loss of life, and causes instability in both economic and social components of the affected nation (Webcache 2).