Advertisement Upgrade to remove ads

Last two lectures after the midterm.

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)

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set