Under the Boardwalk: Coastal Geomorphology

• What to look for while you're on the beach during spring break.

What Causes Changes in Sea Level?

• Answer Varies with Time Scale.

Long-Term Changes in Sea Level

• Shape and Volume of Ocean Basins – Varies with Sea-Floor Spreading Rates

• Slow Spreading = Deeper Ocean Basins• Fast Spreading = Shallower Ocean Basins &

Seas Spill on to Continents

• Volume of Glacier Ice ~225 ft Higher if All Glaciers Melt~400 ft Lower at Pleistocene Maximum

Sea Level Variation in Last 700,000 years

Long-Term Changes in Sea Level• Volume of Glacier Ice

– Pleistocene “Ice Age” 400-500 ft Lower

Estuaries =Drowned River

Valleys:

Delaware Bay, Cheaspeake Bay,Pamlico Sound,

Albemarle Sounds

Eroded During Glacial Low Sea-

Level Stands, Drowned During Interglacial High Sea-Level Stands

Chesapeake Bay

Bathymetry

Susquehanna Paleo-River

Last Century: Ocean Warming & Expansion, Glacial Melting

Seismic Sea Waves (Tsunami) Short

Term Changes

in Sea Level

• Seismic Sea Waves (Tsunami)

Tides - Why?

• Gravity of the Moon and Sun Acting on Ocean Surface

• 24 Hr 50 Min: 2 Highs, 2 Lows

Tides - Why?

• Spring Tide = Highest High Tide & Lowest Low Tide

• Neap Tide =Less Tide Range

Why is there a

high tide on the earth

opposite of the

moon?

Why is there a

high tide on the earth

opposite of the

moon?

Think “Bolo”

Tides Can Be Enhanced or Reduced by the Shape and

Size of a Basin• Gulf of Maine, Bay of Fundy• Mediterranean Sea

The “Med” - Puny Tides

Straits of Straits of GibraltarGibraltar

Bay of Fundy-

“Mongo”Tides

What is Deadliest Day in U.S. History?

• San Francisco Quake, 1906 ~ 500 Dead?• Hurricane Katrina, 2005 > 1420 Dead #• Johnstown Flood of 1889 ~ 2209 Dead?• Pearl Harbor, Dec 7 1941 ~ 2471 Dead #• 11 September 2001 ~ 2986 Dead #• November 1918 Flu ~ 3000 Every Day• Antietam, 17 Sept 1862 3650 Dead

(23,000 casualties. NPS: ~ 4000 may have died later)

• Issac’s Storm, 1900: ~ 8000 Dead in Galveston, Texas Alone!

# From Wikipedia, the free encyclopedia

Antietam/Sharpsburg 17 Sep 1862Casualties in 3 categories: 1) dead; 2) wounded; and 3) missing or captured.

Approximate Numbers Union Confederate TotalKilled 2,100 1,550 3,650

Wounded 9,550 7,750 17,300Missing/Captured 750 1,020 1,770

Total 12,400 10,320 22,720

• These are the approximate numbers for September 17th, 1862. No one knows the actual number of men who would later die of their wounds or the number of missing who had been killed. If you take a conservative estimate of 20% of the wounded dying of their wounds and 30% of the missing killed, the approximate number of soldiers that died as a result of this battle are 7,640.

Storm Surge

“Wave” created by low atmospheric pressure “sucking” ocean water into center of storm

Add pressure map for HurricanCamille

Powerful Low Pressure System (L) Generates Partial Vacuum that draws water into a large wave (storm surge)

31 October 2000 Upper-Air “Weather” Map from Environment Canada/ d ti /t h id / d l 9 t li d th j t t ht l

L

Isaac’s Storm:

The 1900 “Galveston”Hurricane

Galveston Hurricane 1900 Storm Surge Map

Tipped House, Galveston, 1900

Debris at Galveston,1900

Debris at Galveston,1900

Galveston, Texas, 1900

Total Destruction at Galveston, Texas, 1900

Lucas Terrace Apartments, BEFORE Galveston Hurricane

Lucas Terrace Apartments,

AFTER Hurricane

Wind Tides

Pamlico & Albemarle

sounds, NC

Westerlies Blow Water Down

Estuaries

Wind -Creates Most Ocean Waves

Wave Height is Controlled by 1. Wind Velocity 2. Fetch = Distance Water Surface is Subjected to Wind

Wind Waves

Waves = Movement of Motion

Wind Waves

SurfSurfSwashSwash

Wave BaseWave Base

SurfSurf

SwashSwash

•• Wave BaseWave Base

Breaking Wave in Shallow Water

Beach TermsSwashSwash SurfSurf BreakersBreakers

BermBermOld Old BermBerm

Wave Erosion-Deposition

• Wash-Over• Refraction• Longshore Current• Londshore Drift

Beach Erosion in the USA

Hurricane Fran 1996

North Carolina Beach before Hurricane Fran, 1996

See Changes in Next Slide

North Carolina Beach after Hurricane Fran, 1996

Wash-Over DepositsSee Changes from Last Slide

Hurricane Fran Damage from Wash-Over

Beach Erosion:

ThirdCape HatterasLighthouse,

North Carolina

Now Relocated in Fourth

Different Site

Stopped Here 13 March 2003

Wave Refraction

Wave Refraction

Longshore Current & Longshore Drift

Longshore Current & Longshore Drift

LSCLSC

LSD

Coastal Structures

• Groins

Coastal Structures: Groins, Ocean City, NJ

Plummer et al., 2005, 10th ed., p. 347Ocean City NJ

USGS Air Photo from

Terraserver.com See also Matthew 7:26

Coastal Structures: New Jersey JettiesPlummer et al., 2005,

10th ed., p. 347

Spit: South Carolina Barrier Islands

HistoricalChanges

in aVirginia Barrier Island

Presque Isle, Lake Erie, PA,image courtesy Chris Schaney

LSD

Stopped Here on 13 March 2006

Baymouth Bar

Primary v. Secondary Coasts (Both Examples from California)

Primary Shoreline, Northern California

Secondary Shoreline, Pensacola Florida

Sandy Primary

Shoreline: AlbemarleSound, NC

“Drowned”Roanoke

River Valley

Sandy Secondary Shoreline:

Outer Banks

Rocky Shoreline: Nova Scotia

Primary, relict from Glaciation

Headland ErosionWave Energy Concentrated on Headlands, Dispersed in Bays

Wave-Cut Landforms

Wave-Cut Beach, California

Wave-Cut Shoreline, California

Idiotic Building

Oregon CoastPhoto by J.S. Kite

High-Energy Rocky Shoreline: Headland, Maine

Reefs Fringing Volcano

Atoll

Eroding Volcanoes with Fringing Reefs

Atoll

Wave-Cut Cliff

MarineTerrace

= Old Wave-Cut Bench

Active Seastacks

Paleo-Seastack

Wave-Cut Bench

Landforms

MarineTerraces

= Old Wave-Cut Benches