Geology Lab

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CoastalProcesseslecture2.pptx

Coastal Processes

Lab 7

Waves

Wave: energy in motion that results from disturbance. The energy that causes this is a disturbance force.

These disturbing forces can be landslides, calving glaciers, seafloor movements like underwater avalanches, volcanic eruptions.

Height, length, period of a wave depends on:

Wind speed

Wind duration

fetch

Types of Wave Breakers

Spilling Breakers

Break gradually over considerable distance

Form on shorelines with gentle offshore slopes

Plunging Breakers

Tend to curl over and break with a single crash

Front is concave, back is convex

Form at shorelines with steeper offshore slopes

Surging breakers

Peak up but surge onto the back without spilling or plunging

Forms when offshore slopes abruptly and wave energy becomes compressed

Wave Refraction

Bending of a wave as it propagates over different depths.

Concentrated energy on headlands causes erosion and deposition of sediments.

Tides

The periodic rising and falling of the water that results from gravitational pull of the moon and the sun’s action on the rotating earth.

Tidal Cycle includes

Flood tide

Ebb tide

Erosional Landforms

sea arch

sea stack

Coastal sediment Transport

Longshore Drift:

Net movement of sediment parallel to the shore.

Longshore current:

A current that flows parallel to the shore just inside the surf zone.

Also called littoral current

Rip current

Movement of water back into the ocean through narrow zones through the surf zone

Coastal Sediment Deposition and landforms

Beaches

accumulation of unconsolidated sediments that covers the shore

they are areas of deposition and are constantly changing

Barrier islands

long narrow accumulation of sand that is separated from the mainland by open water (lagoon, estuaries) or by salt marshes.

Emergent and Submergent Coastlines

Emergent coastlines

a coastline that has experienced a fall in sea level due to global sea level change, local uplift, or isostatic rebound.

Submergent coastline

A coastline hat has experienced a rise in sea level due to global change in sea level or local land subsidence

Coastal land loss by Erosion

Storm impacts

Dune and beach recession

Dune and beach breeching and overwash

Barrier island breeching

El Nino effects

Landslides and cliff retreat

Human activities

Mitigation of coastal erosion

Hard stabilization

jetties

groins

seawalls

breakwaters

Soft stabilization

beach nourishment

Abandonment