Waves Pt 2
About this set
Created by:
chantelc on December 5, 2011
Description:
Last two lectures after the midterm.
Classes:
EOSC 114, AOII Takes on EOSC 114
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Terms | Definitions |
|---|---|
 Tsunami causes | Earthquakes Volcanic eruptions meteor impacts (biggest) landslides icebergs falling from glaciers (smallest) |
| Shoaling | When a tsunami comes ashore (wavelength drops, height increases, period stays the same) |
| Tsunami vs Wind Driven Wave | Wind: relatively short wavelength/period, breakers arrive & recede quickly Tsunami: ultralong wavelength/period, huge mass of water comes onshore for several minutes |
| 2004 Indian Ocean Tsunami | -deadliest in human history |
| Tsunami waves | -first wave may not be biggest -trough may arrive first -indicator- receding sea level (draw down) |
| Cause: Earthquake | -tectonic plate moving over/under another -vertical motion -possible if sea floor is ruptured |
| Point of Cause: Subduction Zones | -Ring of Fire -Earthquakes create vertical motion -Explosive-character volcanoes exist |
| Cause: Volcanoes | -eruption on land creates landslide into water or earthquake -underwater eruption causes volcano top to move, gas and lava ejected |
| Cause: Landslides | Large displacement of water causing Tsunami |
| Predicting arrival time | -possible because arrival time is based on speed, which depends on water-depth because tsunami are shallow-water waves |
| DART Buoy System | Deep Ocean Assessment & Reporting of Tsunami -measures pressure changes caused by open-ocean tsunami -verifies tsunami existence -communicates info to warning centres |
| Storm Surge | -not a wave, but a local change in sea level (10m+) -can last a few hours- days -amplifies damage from hurricane-driven waves -highest to the right of the eye of hurricane (Northern Hemisphere) |
| Sources: Storm Surge | -low pressure in hurricane eye (small) -high wind speeds (Large!) |
| Eustatic/Global Sea Level Rise | -Formation & melting of ice sheets on land (since last ice age, sea level has risen 120m, if all ice melted it would rise another 60-70m) -Thermal expansion (increased volume due to increased ocean water temp, largest contributor to global sea level rise today!) *we may be underpredicting sea level change! |
| Local/Regional Sea Level Change | -Isostatic rebound (rise/fall of land due to glacier melt [continues today]) -Tectonic movements (Atlantic Coast subsiding, Pacific emerging) |
| Sea Level Rise: Effects | -shorelines move horizontally at about 1000x rate of sea level rise for low slope shores (ex Florida) Therefore, sea level +15cm -> shoreline decreased 150m inwards! |
| Sea Level Rise: May cause... | -submergence of low-lying areas -increased erosion -increased coastal flooding -inundation of natural ecosystems |
| Sea Level Rise: Local effects (BC) | -mainland is submerging, but Vancouver Island is emerging |
| Archimedes' Principle | Floating Sea Ice: any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object |
| Permafrost | -soil frozen throughout the year underlying most of Arctic -reinforces soil, limits erosion -disappearing-> erosion rates increase->threatens coastal areas |
| Melting Ice Risks: Ex. Barrow, Alaska | -protected from storms/waves by: sea ice (absorbs waves, reduces fetch), bluffs (w/ permafrost), and lagoons -without ice: waves crash in, storm surge, lagoons flood, bluffs erode |
| Erosion: Ex. New Orleans | -built on Mississippi delta -sediment builds up in delta-fans out as new, low-elevation land -causes location of river to change over time, resulting in marshy, loose land (natural buffer against waves/storm surge) -city works against this change to lock river in place (and further development) -creates new problems: lack of new material, no river flow to wetlands -causes New Orleans to sink! -natural wetland buffer is easily overwhelmed! (with no material, 30+ miles lost in Katrina can't be replaced) |
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