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 –Sandy beaches of Jersey to Florida and Southern California –subsidence

Erosional Coasts Land sources of erosion: –Stream erosion –Wind abrasion –Plant roots –Freezing/thawing of water in rock cracks Marine sources of erosion: –Waves: water itself or tossed rocks etc –Tides –Marine organisms

Erosional Coasts Effects of erosion depend on: –Hardness of rock Sandstone erodes quickly, granite erodes slowly –Wave energy –Tidal range

–Figure 10.4

Sea cliff and Wave cut platform

Sea Cave – La Jolla, CA

–Figure 10.5

Depositional Coasts Composed of sediment rather than rock- such as beaches Built up by biological activity – such as coral reefs, salt marshes and mangrove swamps

–Figure 10.7

–Fig , p. 261 –Great Barrier Reef, Australia

–Mangrove coast, Florida

Erosional vs Depositional Coasts Some coasts show characteristics of both –Central California is erosional but southern California is depositional Erosional Coast can become depositional coasts –As erosion turns rock to sediment and deposits it on shore Depositional Coasts can still experience erosion

Estuaries Body of water partially surrounded by land where fresh water from a river mixes with ocean water

Estuaries Great biological productivity and diversity –Protection from wave shock –Variety of habitats (salt marshes, mangrove swamps, seagrass meadows, etc) –Availability of nutrients Used as nurseries by many species

Estuaries Characterized by their circulation pattern –Shape of estuary –Volume of river flow –Tidal range

Salt wedge estuaries –Rapid river flow –Low tidal range –Hudson River, Mississippi River Well-mixed estuaries –Slower river flow –High tidal range –Columbia River (Washington and Oregon) Partially mixed estuaries –Rapid river flow –High tidal range –Chesapeake Bay (Maryland and Virginia)

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 –Winter and storms erode and flatten beaches

–Figure 10.2a

–Figure 10.2d

–Fig c, p. 254

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 10.19

Groin Field Cape May, NJ

–Figure 10.20: Jetties

–Figure –Santa Cruz Harbor, CA

Break water Santa Monica, CA

–Figure 10.24: Seawalls

Alternative: Beach Replenishment

–Figure 10.26

–Figure 10.B: Relocation