Tsunami: Interesting Facts and F.A.Q
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Wind-Caused Waves Misleads Us Energy Is Transferred to the Wave
WAVES IN WATER is quite similar. Most waves are created by the frictional drag of wind blowing across the water surface. A wave begins as Tsunami can be the most overwhelming of all waves, but a tiny ripple. Once formed, the side of a ripple increases the their origins and behaviors differ from those of the every day waves we see at the seashore or lakeshore. The familiar surface area of water, allowing the wind to push the ripple into waves are caused by wind blowing over the water surface. a higher and higher wave. As a wave gets bigger, more wind Our experience with these wind-caused waves misleads us energy is transferred to the wave. How tall a wave becomes in understanding tsunami. Let us first understand everyday, depends on (1) the velocity of the wind, (2) the duration of wind-caused waves and then contrast them with tsunami. time the wind blows, (3) the length of water surface (fetch) the wind blows across, and (4) the consistency of wind direction. Once waves are formed, their energy pulses can travel thou Wind-Caused Waves sands of kilometers away from the winds that created them. Waves transfer energy away from some disturbance. Waves moving through a water mass cause water particles to rotate in WHY A WIND-BLOWN WAVE BREAKS place, similar to the passage of seismic waves (figure 8.5; see Waves undergo changes when they move into shallow water figure 3.18). You can feel the orbital motion within waves by water with depths less than one-half their wavelength. -
Ocean Trench
R E S O U R C E L I B R A R Y E N C Y C L O P E D I C E N T RY Ocean trench Ocean trenches are long, narrow depressions on the seafloor. These chasms are the deepest parts of the ocean—and some of the deepest natural spots on Earth. G R A D E S 5 - 12+ S U B J E C T S Earth Science, Geology, Geography, Physical Geography C O N T E N T S 11 Images, 1 Video, 2 Links For the complete encyclopedic entry with media resources, visit: http://www.nationalgeographic.org/encyclopedia/ocean-trench/ Ocean trenches are long, narrow depressions on the seafloor. These chasms are the deepest parts of the ocean—and some of the deepest natural spots on Earth. Ocean trenches are found in every ocean basin on the planet, although the deepest ocean trenches ring the Pacific as part of the so-called “Ring of Fire” that also includes active volcanoes and earthquake zones. Ocean trenches are a result of tectonic activity, which describes the movement of the Earth’s lithosphere. In particular, ocean trenches are a feature of convergent plate boundaries, where two or more tectonic plates meet. At many convergent plate boundaries, dense lithosphere melts or slides beneath less-dense lithosphere in a process called subduction, creating a trench. Ocean trenches occupy the deepest layer of the ocean, the hadalpelagic zone. The intense pressure, lack of sunlight, and frigid temperatures of the hadalpelagic zone make ocean trenches some of the most unique habitats on Earth. -
Geologists Suggest Horseshoe Abyssal Plain May Be Start of a Subduction Zone 8 May 2019, by Bob Yirka
Geologists suggest Horseshoe Abyssal Plain may be start of a subduction zone 8 May 2019, by Bob Yirka against one another. Over by the Iberian Peninsula, the opposite appears to be happening—the African and Eurasian plates are pulling apart as the former creeps east toward the Americas. Duarte noted that back in 2012, other researchers conducting seismic wave tests found what appeared to be a dense mass of unknown material beneath the epicenter of the 1969 quake. Some in the field suggested it could be the start of a subduction zone. Then, last year, another team conducted high-resolution imaging of the area and also found evidence of the mass, confirming that it truly existed. Other research has shown that the area just above the mass experiences routine tiny earthquakes. Duarte suggests the evidence to date indicates that the bottom of the plate is peeling away. This could happen, he explained, due to serpentinization in which water percolates through plate fractures and reacts with material beneath the surface, resulting A composite image of the Western hemisphere of the in the formation of soft green minerals. The soft Earth. Credit: NASA mineral layer, he suggests, is peeling away. And if that is the case, then it is likely the area is in the process of creating a subduction zone. He reports that he and his team members built models of their A team of geologists led by João Duarte gave a ideas and that they confirmed what he suspected. presentation at this past month's European The earthquakes were the result of the process of Geosciences Union meeting that included a birthing a new subduction zone. -
Tsunami, Seiches, and Tides Key Ideas Seiches
Tsunami, Seiches, And Tides Key Ideas l The wavelengths of tsunami, seiches and tides are so great that they always behave as shallow-water waves. l Because wave speed is proportional to wavelength, these waves move rapidly through the water. l A seiche is a pendulum-like rocking of water in a basin. l Tsunami are caused by displacement of water by forces that cause earthquakes, by landslides, by eruptions or by asteroid impacts. l Tides are caused by the gravitational attraction of the sun and the moon, by inertia, and by basin resonance. 1 Seiches What are the characteristics of a seiche? Water rocking back and forth at a specific resonant frequency in a confined area is a seiche. Seiches are also called standing waves. The node is the position in a standing wave where water moves sideways, but does not rise or fall. 2 1 Seiches A seiche in Lake Geneva. The blue line represents the hypothetical whole wave of which the seiche is a part. 3 Tsunami and Seismic Sea Waves Tsunami are long-wavelength, shallow-water, progressive waves caused by the rapid displacement of ocean water. Tsunami generated by the vertical movement of earth along faults are seismic sea waves. What else can generate tsunami? llandslides licebergs falling from glaciers lvolcanic eruptions lother direct displacements of the water surface 4 2 Tsunami and Seismic Sea Waves A tsunami, which occurred in 1946, was generated by a rupture along a submerged fault. The tsunami traveled at speeds of 212 meters per second. 5 Tsunami Speed How can the speed of a tsunami be calculated? Remember, because tsunami have extremely long wavelengths, they always behave as shallow water waves. -
Tsunamis in Alaska
Tsunami What is a Tsunami? A tsunami is a series of traveling waves in water that are generated by violent vertical displacement of the water surface. Tsunamis travel up to 500 mph across deep water away from their generation zone. Over the deep ocean, there may be very little displacement of the water surface; but since the wave encompasses the depth of the water column, wave amplitude will increase dramatically as it encounters shallow coastal waters. In many cases, a El Niño tsunami wave appears like an endlessly onrushing tide which forces its way around through any obstacle. The image on the left illustrates how the amplitude of a tsunami wave increases as it moves from the deep ocean water to the shallow coast. Over deep water, the wave length is long, and the wave velocity is very fast. By the time the wave reaches the coast, wave length decreases quickly and wave speed slows dramatically. As this takes place, wave height builds up as it prepares to inundate the shore. Why do Tsunamis occur in Alaska? Subduction-zone mega-thrust earthquakes, the most powerful earthquakes in the world, can produce tsunamis through fault boundary rupture, deformation of an overlying plate, and landslides induced by the earthquake (IRIS, 2016). Megathrust earthquakes occur along subduction zones, such as those found along the ring of fire (see image to the right). The ring of fire extends northward along the coast of western North America, then arcs westward along the southern side of the Aleutians, before curving southwest along the coast of Asia. -
2018 NOAA Science Report National Oceanic and Atmospheric Administration U.S
2018 NOAA Science Report National Oceanic and Atmospheric Administration U.S. Department of Commerce NOAA Technical Memorandum NOAA Research Council-001 2018 NOAA Science Report Harry Cikanek, Ned Cyr, Ming Ji, Gary Matlock, Steve Thur NOAA Silver Spring, Maryland February 2019 NATIONAL OCEANIC AND NOAA Research Council noaa ATMOSPHERIC ADMINISTRATION 2018 NOAA Science Report Harry Cikanek, Ned Cyr, Ming Ji, Gary Matlock, Steve Thur NOAA Silver Spring, Maryland February 2019 UNITED STATES NATIONAL OCEANIC National Oceanic and DEPARTMENT OF AND ATMOSPHERIC Atmospheric Administration COMMERCE ADMINISTRATION Research Council Wilbur Ross RDML Tim Gallaudet, Ph.D., Craig N. McLean Secretary USN Ret., Acting NOAA NOAA Research Council Chair Administrator Francisco Werner, Ph.D. NOAA Research Council Vice Chair NOTICE This document was prepared as an account of work sponsored by an agency of the United States Government. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency or Contractor thereof. Neither the United States Government, nor Contractor, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, product, or process disclosed, or represents that its use would not infringe privately owned rights. Mention of a commercial company or product does not constitute an endorsement by the National Oceanic and Atmospheric Administration. -
3.16 Oceanic Plateaus A.C.Kerr Cardiffuniversity,Wales,UK
3.16 Oceanic Plateaus A.C.Kerr CardiffUniversity,Wales,UK 3.16.1 INTRODUCTION 537 3.16.2 FORMATION OF OCEANIC PLATEAUS 539 3.16.3 PRESERVATIONOFOCEANIC PLATEAUS 540 3.16.4GEOCHEMISTRY OF CRETACEOUSOCEANICPLATEAUS 540 3.16.4.1 GeneralChemicalCharacteristics 540 3.16.4.2 MantlePlumeSource Regions ofOceanic Plateaus 541 3.16.4.3 Caribbean–ColombianOceanic Plateau(, 90 Ma) 544 3.16.4.4OntongJavaPlateau(, 122 and , 90 Ma) 548 3.16.5THE INFLUENCE OF CONTINENTALCRUST ON OCEANIC PLATEAUS 549 3.16.5.1 The NorthAtlantic Igneous Province ( , 60 Ma to Present Day) 549 3.16.5.2 The KerguelenIgneous Province ( , 133 Ma to Present Day) 550 3.16.6 IDENTIFICATION OF OCEANIC PLATEAUS IN THE GEOLOGICAL RECORD 551 3.16.6.1 Diagnostic FeaturesofOceanic Plateaus 552 3.16.6.2 Mafic Triassic Accreted Terranesinthe NorthAmericanCordillera 553 3.16.6.3 Carboniferous to CretaceousAccreted Oceanic Plateaus inJapan 554 3.16.7 PRECAMBRIAN OCEANICPLATEAUS 556 3.16.8ENVIRONMENTAL IMPACT OF OCEANICPLATEAU FORMATION557 3.16.8.1 Cenomanian–TuronianBoundary (CTB)Extinction Event 558 3.16.8.2 LinksbetweenCTB Oceanic PlateauVolcanism andEnvironmentalPerturbation 558 3.16.9 CONCLUDING STATEMENTS 560 REFERENCES 561 3.16.1 INTRODUCTION knowledge ofthe oceanbasins hasimproved over the last 25years,many moreoceanic plateaus Although the existence oflarge continentalflood havebeenidentified (Figure1).Coffinand basalt provinceshasbeenknownfor some Eldholm (1992) introduced the term “large igneous considerabletime, e.g.,Holmes(1918),the provinces” (LIPs) asageneric term encompassing recognition thatsimilarfloodbasalt provinces oceanic plateaus,continentalfloodbasalt alsoexist belowthe oceans isrelatively recent. In provinces,andthoseprovinceswhich form at the early 1970s increasingamounts ofevidence the continent–oceanboundary (volcanic rifted fromseismic reflection andrefraction studies margins). -
Atlantic Hurricane Activity During the Last Millennium
www.nature.com/scientificreports OPEN Atlantic hurricane activity during the last millennium Michael J. Burn1 & Suzanne E. Palmer2 Received: 13 February 2015 Hurricanes are a persistent socio-economic hazard for countries situated in and around the Accepted: 10 July 2015 Main Development Region (MDR) of Atlantic tropical cyclones. Climate-model simulations have Published: 05 August 2015 attributed their interdecadal variability to changes in solar and volcanic activity, Saharan dust flux, anthropogenic greenhouse gas and aerosol emissions and heat transport within the global ocean conveyor belt. However, the attribution of hurricane activity to specific forcing factors is hampered by the short observational record of Atlantic storms. Here, we present the Extended Hurricane Activity (EHA) index, the first empirical reconstruction of Atlantic tropical cyclone activity for the last millennium, derived from a high-resolution lake sediment geochemical record from Jamaica. The EHA correlates significantly with decadal changes in tropical Atlantic sea surface temperatures (SSTs; r = 0.68; 1854–2008), the Accumulated Cyclone Energy index (ACE; r = 0.90; 1851–2010), and two annually-resolved coral-based SST reconstructions (1773–2008) from within the MDR. Our results corroborate evidence for the increasing trend of hurricane activity during the Industrial Era; however, we show that contemporary activity has not exceeded the range of natural climate variability exhibited during the last millennium. The extent to which the climate dynamics of the Main Development Region (MDR) of Atlantic tropical cyclone activity are controlled by natural or anthropogenic climatic forcing factors remains unclear1,2. This uncertainty has arisen because of the reliance on historical meteorological records, which are too short to capture the natural long-term variability of climatic phenomena as well as a lack of understand- ing of the physical link between tropical Atlantic SSTs and tropical cyclone variability3,4. -
EARTH SCIENCE ACTIVITY #1 Tsunami in a Bottle
EARTH SCIENCE ACTIVITY #1 Grades 3 and Up Tsunami in a Bottle This activity is one of several in a basic curriculum designed to increase student knowledge about earthquake science and preparedness. The activities can be done at any time in the weeks leading up to the ShakeOut drill. Each activity can be used in classrooms, museums, and other educational settings. They are not sequence-bound, but when used together they provide an overview of earthquake information for children and students of various ages. All activities can be found at www.shakeout.org/schools/resources/. Please review the content background (page 3) to gain a full understanding of the material conducted in this activity. OBJECTIVE: For students to learn that tsunamis can be caused by earthquakes and to understand the effects of tsunamis on the shoreline MATERIALS/RESOURCES NEEDED: 2-liter plastic soda bottles Small gravel (fish tank gravel) Water source Empty water bottle (16 oz) Overhead projector Transparency of Tsunami Facts “What Do I See?” handout PRIOR KNOWLEDGE: In order to conduct this activity, students need to know how fault slippage can generate earthquakes. ACTIVITY: Set-Up (Time varies) Collect as many 2-liter soda bottles as possible or ask students to bring in bottles for this activity (3 students can share one bottle). Obtain an empty water bottle (about 16 oz). Remove labels from all bottles. Purchase or gather enough small gravel to fit through the mouth of the soda bottles. Students will fill up their soda bottles with gravel to create at least a 2 inch layer on the bottom of the bottle. -
Geometrical Effects of a Subducted Seamount on Stopping Megathrust
GEOPHYSICAL RESEARCH LETTERS, VOL. 40, 1–6, doi:10.1002/grl.50509, 2013 Geometrical effects of a subducted seamount on stopping megathrust ruptures Hongfeng Yang,1,2 Yajing Liu,1,3 and Jian Lin1 Received 6 March 2013; revised 18 April 2013; accepted 25 April 2013. [1] We have numerically simulated dynamic ruptures along rich sediments into seismogenic zone [Bangs et al., 2006]. a “slip-weakening” megathrust fault with a subducted The presence of entrained fluid-rich sediments in the vicinity seamount of realistic geometry, demonstrating that of a subducted seamount would reduce effective normal seamounts can act as a barrier to earthquake ruptures. Such stress and lubricate the thrust interface, leading to little barrier effect is calculated to be stronger for increased elastic strain accumulation and thus inhibiting coseismic seamount normal stress relative to the ambient level, for ruptures [Mochizuki et al., 2008; Singh et al., 2011]. Further- larger seamount height-to-width ratio, and for shorter more, it was proposed that seamount subduction may create seamount-to-nucleation distance. As the seamount height a complex fracture network in the overriding plate, making it increases from 0 to 40% of its basal width, the required unfavorable for the generation of large earthquakes [Wang increase in the effective normal stress on the seamount to and Bilek, 2011]. Thus, the specific mechanisms for stop ruptures drops by as much as ~20%. We further subducted seamounts to stop coseismic ruptures could be demonstrate that when a seamount is subducted adjacent to complex and remain open for debate. the earthquake nucleation zone, coseismic ruptures can be [3] Previous numerical studies have modeled a subducted stopped even if the seamount has a lower effective normal seamount as a patch under elevated effective normal stress stress than the ambient level. -
Distribution and Sedimentary Characteristics of Tsunami Deposits
Sedimentary Geology 200 (2007) 372–386 www.elsevier.com/locate/sedgeo Distribution and sedimentary characteristics of tsunami deposits along the Cascadia margin of western North America ⁎ Robert Peters a, , Bruce Jaffe a, Guy Gelfenbaum b a USGS Pacific Science Center, 400 Natural Bridges Drive, Santa Cruz, CA 95060, United States b USGS 345 Middlefield Road, Menlo Park, CA 94025, United States Abstract Tsunami deposits have been found at more than 60 sites along the Cascadia margin of Western North America, and here we review and synthesize their distribution and sedimentary characteristics based on the published record. Cascadia tsunami deposits are best preserved, and most easily identified, in low-energy coastal environments such as tidal marshes, back-barrier marshes and coastal lakes where they occur as anomalous layers of sand within peat and mud. They extend up to a kilometer inland in open coastal settings and several kilometers up river valleys. They are distinguished from other sediments by a combination of sedimentary character and stratigraphic context. Recurrence intervals range from 300–1000 years with an average of 500–600 years. The tsunami deposits have been used to help evaluate and mitigate tsunami hazards in Cascadia. They show that the Cascadia subduction zone is prone to great earthquakes that generate large tsunamis. The inclusion of tsunami deposits on inundation maps, used in conjunction with results from inundation models, allows a more accurate assessment of areas subject to tsunami inundation. The application of sediment transport models can help estimate tsunami flow velocity and wave height, parameters which are necessary to help establish evacuation routes and plan development in tsunami prone areas. -
Subduction Zones”
EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Open Access Biogeosciences Biogeosciences Discussions Open Access Open Access Climate Climate of the Past of the Past Discussions Open Access Open Access Earth System Earth System Dynamics Dynamics Discussions Open Access Geoscientific Geoscientific Open Access Instrumentation Instrumentation Methods and Methods and Data Systems Data Systems Discussions Open Access Open Access Geoscientific Geoscientific Model Development Model Development Discussions Open Access Open Access Hydrology and Hydrology and Earth System Earth System Sciences Sciences Discussions Open Access Open Access Ocean Science Ocean Science Discussions Open Access Solid Earth, 4, 129–133, 2013 Open Access www.solid-earth.net/4/129/2013/ Solid Earth doi:10.5194/se-4-129-2013 Solid Earth Discussions © Author(s) 2013. CC Attribution 3.0 License. Open Access Open Access The Cryosphere The Cryosphere Discussions Introduction to the special issue on “Subduction Zones” S. J. H. Buiter1,2, F. Funiciello3, and J. van Hunen4 1Geological Survey of Norway, Geodynamics Team, Leiv Eirikssons vei 39, 7040 Trondheim, Norway 2University of Oslo, The Centre for Earth Evolution and Dynamics, 0316 Oslo, Norway 3Universita` Roma Tre, Dipartimento di Scienze, L.go S. Leonardo Murialdo 1, 00146, Rome, Italy 4Durham University, Department of Earth Sciences, Durham DH1 3LE, UK Correspondence to: S.