““The sea heaves up, hangs loaded o'er the The sea heaves up, hangs loaded o'er the land, Breaks there, and buries its tumultuous land, Breaks there, and buries its tumultuous

strength.strength. ” ”

— — Robert Browning Hamilton Robert Browning Hamilton (Brainyquote.com)(Brainyquote.com)

The Impact of Waves and Currents on the Landscape

Coastal Processes Coastal Landforms

Coastal Processes and Terrain

The Impact of Waves and Currents on the Landscape• Coastal Processes

– Erosion – by waves, mainly– Deposition – by currents, mainly

• Rocky cliffs and headlands– Main erosional features

• Beaches and sandbars– Main depositional features

Coastal Processes• Erosion and Deposition

– Involves the transfer of energy from the atmosphere (wind) to the hydrosphere (ocean) and then to the lithosphere (land).

Kinetic energy transfer

Wind Deposition

Erosion

Wind

Coast

WavesAnimation • Definition – A disturbance in water caused by energy

passing through it.• Wave terms: wavelength, wave crest and trough,

swash

1. Wave Motion and Wave Refraction2. Tsunami

– Fig. 20-2

– Wave Refraction (see previous animation)

– Fig. 20-5

– Fig. 20-6. Headland erosion in Australia along the southern coast of the state of Victoria, read caption, pg 592.

Formation of Arches

– Wave Erosion, see caption, pg 593• Hydraulic pounding and sea cliff erosion• Chemical action (some rocks are soluble in sea water)

– Fig. 20-7 Formation of a Wave-Cut Notch

– Wave Erosion

– Fig. 20-7 Formation of a Wave-Cut Notch

NotchWave-cut platform

Cliff face

Sea Level

Former shore

• TidesAnimation (Tides)

– Significant erosion agents in narrow bays, margins of shallow seas, and straits.

• Fig. 20-9. Bay of Fundy has the highest tidal range in the world. Tidal action created these pedestal rocks on the edge of the bay, read caption, pg 595.

• Changes in Sea Level and Lake Level– Due to:

• Tectonic uplift or sinking of landmass• Eustatic – increase or decrease in the volume of water in the

oceans (Pleistocene glaciations). Also, global warming.

– Fig. 20-10. Northern California coast is experiencing tectonic uplift.

• Currents and Coastal Sediment Transport– Longshore Currents (see next slide and stabilization

animation)• Wave refraction

– Beach Drifting• Particle-by-particle transport of beach material

Figure 20-12

– Fig. 20-13. Waves approaching the shore obliquely causes longshore currents and beach drifting.

• Coastal Deposition– Based on the sediment

budget of a shore• Deposition mainly occurs

when inputs from longshore current and wave action exceeds outputs from storm wave action.

– E.g. large beaches and sand dunes

• Fig. 20-14. One of the largest coastal dune accumulations is on the Oregon coast.

Fig. 20-14

Coastal Landforms• Depositional Landforms

– Beaches• Most widespread marine dispositional feature on land

(mostly sand deposits)

– Fig. 20-15 Components of the beach environment

– Spit and related features• Spit: Linear strand of marine sediments attached to shore• Formation usually involves longshore current transport• Related features

– Fig. 20-16. Types of spits and the longshore current.

• Idealized drawings of formation of spit and related features

(3) Baymouth bar(2) Hook

Land

Ocean

Bay

(1) Simple spit

• Photographs of spits and related features

– Fig. 20-17. Spit at Cape Henlopen, Delaware

• Tombolo formation

Land Ocean

Small island / sea stack

– Fig. 20-18. Tombolo and Mont Saint Michel on the northwest coast of France.

– Barrier Islands (also, Fig 20-20, pg 602)• Coastal islands, parallel to the mainland shore• Complex origins

– Pleistocene sediments washed toward mainland or longshore transport and spit segmentation

• Lagoon formation– Landward side of barrier island, protected from large waves– Low energy environment, fine mud deposits (tidal flats)

– Fig. 20-19

– Human Alteration of Coastal Sediment Budgets• Beach starvation (unintentionally shrinking beaches)

– Dam construction on rivers reduces sediment discharge into oceans, starving nearby beaches of sand

– Old debris dam in Santa Ynez Mountains, near Santa Barbara, CA (Richard A. Crooker photo)

• Beach nourishment (re-building beaches)– Adding sand to beaches by dredging and pumping sand

from off-shore

– A slurry of sand and water is pumped on shore and the sand is spread onto the beach of Rehoboth Beach, DE (Richard A. Crooker photos) (overlay)

• Beach preservation (maintaining beaches)– Build structures that modify longshore transport and wave

action in order to keep sand on beaches

– Jetties and groins (see personal pictures)

– Fig. 20-22

Animation (Coastal Stabilization Structures)

• Shorelines of Submergence– Ria Shorelines (formed at the end of the last ice age)

• Hilly or mountainous areas– flooded valleys become estuaries (long fingers of seawater

projecting inland). Dams also create similar landforms, although these are technically not estuaries (see photos of Hoover Dam).

- Fig. 20-23, Chesapeake Bay. Read caption, pg 603.

– Fjorded Coasts• Fjord – glacial trough that is cut so deep that it is

inundated by the sea (after glacial melting)

– Fig. 20-24

– Wave-Cut Cliffs and Platforms (photo, pg 604)– Marine Terraces are uplifted landforms (captions, pg 605)

- Fig. 20-26 and 27. Near Fort Ross, CA

• Shorelines of Emergence

• Coral Coasts– Coral Polyps

• Reef-building creatures, in warm tropical waters

– Fig. 20-28

– Fig. 20-31, read caption

– Sinking Islands• Three types of reefs

Sea Level

Fringing

Sea Level Barrier

Sea Level Atoll

– Fig. 20-32. Part of the fringing reef on the island of Moorea, French Polynesia.

– Shallow-water Platforms• Australia’s Great Barrier Reef

– Fig. 20-30