The Coast temporary junctions between land and sea are subject to change –waves, currents, tides, biological processes, tectonic activity position changes as sea-level does

Sea level 18,000 years ago during last ice age

If sea level rises 60m (200ft) and floods 250 km (160 mi) inland

Classification of Coasts Erosional Coasts –Dominant process is removal of material –Rocky shores of Maine and central California –Tectonic uplift Depositional Coasts –Dominant process is the accumulation of material Example = beaches –Sandy beaches of Jersey to Florida and Southern California –subsidence

Beaches a zone of loose particles that covers part of the shore extends from a landward limit –cliff, permanent dunes, seawall extends to the seaward limit where movement of sediment on and offshore ceases

–Figure 10.1

Beach Profiles Steepness of beaches change with seasons and storms –Summer and calm periods build up beaches Swash dominates (soaks into beach), less backwash –Winter and storms erode and flatten beaches Backwash dominates, very little swash soaks in because beach is saturated)

–Figure 10.2a –Wide berm –Steep beach face

–Figure 10.2d –Narrow berm –Flatter beach face –longshore bar

–Fig c, p. 254 –Seasonal Changes on a beach in California

Beach Profiles Steepness depends on sediment size –Beaches with larger particles tend to be steeper –Smaller particles result in flatter beaches

Beaches exist in a delicate balance between accumulation and destruction Waves can transport sand onshore or offshore Longshore currents transport sand along the coastline

–Figure 10.3b

–Figure 10.7

–Figure 10.8 –Martha’s Vineyard, MA –Great Rock Beach, CA

Barrier Islands Are essentially large sand bars Protect the coast behind them Very unstable themselves

–Figure 10.9 –Tom’s River, NJ

Heavily developed barrier island: Ocean City, MD

–Figure Barrier Island Migration

–Fig , p. 258

Human Impact on Beaches Attempts to “save” beaches or property often fail or make matters worse

–Figure 10.18: Groins

–Figure –Shipbottom, NJ

Groin Field Cape May, NJ

–Figure 10.20: Jetties

–Figure –Santa Cruz Harbor, CA

Break water Santa Monica, CA

–Designed to protect harbors from waves –Can cause excessive erosion, requiring dredging to keep area stable

–Figure 10.24: Seawalls

Alternative: Beach Replenishment

–Figure 10.26

–Figure 10.B: Relocation