Coastal ClassificationCoastal Classification
Most group coastal areas into classes that have similar features because of having developed in similar geological and environmental
settings.
By its very nature, the coast is an incredibly complex and diverse environment, one that may defy organization into neat compartments.
Nevertheless, the quest for understanding how shorelines form and how human activities affect these processes has led the creation of
classification schemes.
This is called the “geologic framework” andIt is the motivating ideal behind the USGS Marine and
Coastal Geology Program
Headlands, Embayments,Tombolos, Channel Mouths, Beaches, Tidal Flats, Estuaries
Shepard’s 1973 ClassificationShepard’s 1973 Classification
Divides the world’s coasts into primary coasts – formed mostly by non-marine agents - and
secondary coasts - shaped primarily by marine processes.
Further subdivisions occur according to which specific agent, terrestrial or marine, had the greatest influence
on coastal development.
Although gradational shore types exist, which are difficult to classify, most coasts show only one dominant influence.
Primary coast – nonmarine agent
Secondary coast – marine agent
Primary CoastsPrimary CoastsLand Erosion CoastsLand Erosion Coasts
Land erosion coasts Shaped by subaerial erosion and partly drowned by postglacial rise of sea level.
Ria Coasts (Chesapeake Bay)
Dendritic (flooded drainage in horizontal beds)
Trellis (glacial erosion, fjords, Gulf St. Lawrence)Drowned Karst Topography (northwest Florida)
Land Erosion Coast – Ria Coast
Florida, flooded karsterosion due to dissolutionflooded by sea-level rise
Glacier Bay, flooded fjorderosion by glaciationflooded by sea-level rise
Primary CoastsPrimary CoastsSubaerial Deposition CoastsSubaerial Deposition Coasts
River deposition coasts Deltaic coasts (Mississippi Delta) Compound delta coasts (north slope - Pt. Barrow
to MacKenzie River) Compound alluvial fan (straightened by erosion) Glacial deposition coasts (Cape Cod) Wind deposition coasts (Sleeping Bear St. Park) Landslide coasts (Martinique)
Cape Cod regionglacial deposition
Mississippi deltasubaerial deposition
Sleeping Bear, Michigansubaerial deposition, dune
Primary CoastsPrimary CoastsVolcanic CoastsVolcanic Coasts
Lava Flow Coasts (Big Island)Tephra CoastsVolcanic Collapse Coasts (Hanauma Bay)
Primary Volcanic Coast
Collapsed Volcanic Coast
Pyroclastic surgeMontserrat
Primary CoastsPrimary CoastsShaped by Diastrophic MovementsShaped by Diastrophic Movements
Fault CoastsFold CoastsSedimentary Extrusions (salt domes, mud
lumps, Red Sea)
Diastrophism – movement of the crust
Primary CoastsPrimary CoastsIce CoastsIce Coasts
Glacial Ice and Sea Ice
Primary Ice CoastCollapsing Larson B ice shelf
Wave-straightened cliffsMade irregular by wave erosion
Secondary CoastsSecondary CoastsWave Erosion CoastsWave Erosion Coasts
Wave straightened cliffs
Maui lava flows – irregular erosion resistance
Secondary CoastsSecondary CoastsMarine Deposition CoastsMarine Deposition Coasts
Barrier CoastsCuspate forelandsBeach PlainsMud Flats/Salt Marshes
Primary Marine DepositionCuspate Foreland Coast
Holocene beachStrand plain
Coral Reef CoastSerpulid Reef CoastOyster Reef CoastMangrove CoastMarsh Grass Coast
Secondary CoastsSecondary CoastsCoasts Built by OrganismsCoasts Built by Organisms
Submergent Coasts•Relative sea level is rising•Estuaries formed in drowned river mouths
Emergent Coasts•Relative sea level is falling•Tectonics or isostasy responsible for most types
Depositional Coasts•Wide sandy beaches, stream deltas, overabundance of sediment
Erosional Coasts•Irregular coastline, narrow beaches, eroding headlands
Convergent Coasts•Sea Cliffs common, narrow continental shelf, relatively straight and mountainous
Other Classification Schemes
Passive Margin Coasts•Broad continental shelf•Plate trailing edge
Submergent Coast
Emergent Coast
Depositional Coast – Mississippi River Delta
Erosional Coast – “12 Apostles”
Convergent Coast –
Trailing Coast –
Delta Classification-tide dominated-river dominated-wave dominated
Shorelines straighten with time