Coastal classification
Sediments
Coastal Dynamics
1
Coastal Classification
 Geologic classification – based on
tectonic activity
 Active coasts = close to plate boundaries
 Passive coasts = far from plate boundaries
 Formation & classification of coasts
 Primary coasts – formed by geologic
activity
 Secondary coasts– formed by oceanic
processes
 Combination coasts – formed by both
geologic activity and oceanic processes.
2
Primary coastlines
 Formed by land-based erosion,
sedimentation, volcanic activity, and
tectonic activity
1.
Erosion coasts – form by land-based
erosion

2.
Coasts formed by sedimentation –
sediments carried downriver are
deposited

3.
Eg. Some estuaries
form deltas and some estuaries
Volcanic coasts – formed by volcanoes

Ex. Hawaii
4. Tectonic coasts (fault coasts) – form as
plates collide and cause uplift
3
Secondary coasts
 Result from marine/oceanic processes
1. Wave-erosion coasts – pounding of
waves erodes and changes a coastline
over time

Rocky coasts
2. Marine-deposition coasts – ocean
sediments are deposited and
accumulate in one place

Barrier islands, beaches, some
estuaries
3. Coasts build by marine organisms
– caused by biologic activity

Coral reefs, oyster shells, mangrove
swamps
4
Types & Origins of Sediments
 Lithogenous sediments = from land erosion
or volcanic eruptions
 Quartz & clay
 Biogenous sediments = from organisms
 Silica & calcium carbonate
 Hydrogenous sediments = result from
chemical reactions within seawater
 Less than 1% of sediments
 Cosmogenous sediments = from outer
space
 Cosmic dust & debris
 Least abundant of all sediments
5
Sediment sizes
 Sediments are classified by
grain size
 Grain size and current
strength effects:
 How quickly sediments
erode
 Where they settle from the
water
6
Sediment Sizes, cont.
Classification
Grain Diameter
Example
Clay
Smaller than 0.004 mm
Talc or fine powder
Silt
0.004mm – 0.0625 mm
Powder
Sand
0.0625 mm – 2 mm
Sugar crystals
Granule
2 mm – 4 mm
Aquarium gravel
Pebble
4 mm – 64 mm
Grape
Cobble
64 mm – 256 mm
Cobblestone
Boulder
256 mm and larger
A brick or larger
7
Coastal Sedimentation
 Tides, waves, and
currents affect coastal
sedimentation
 Waves prevent
sediments from settling
 Continental shelves in polar
regions are affected by ice
rafting
 As glaciers & icebergs melt,
sediments are deposited
 Combination of
lithogenous & biogenous
8
Beaches
 Sand
 Comes from erosion of rocks
 Carried by currents long distances from where it is formed
 Beaches are made of three sections:
 Backshore – rarely touched by water, includes dunes or
grasses
 Foreshore – sometimes covered by water (between high tide
and low tide marks)
 Low-tide terrace – flat portion of the foreshore where waves
break
 Beach shape & appearance
 Depend on size of sediments, wave energy, and beach slope
9
Beaches & Longshore drift
 Longshore drift is caused by longshore currents
 Longshore currents strike coastlines at an angle
 Cause sand and sediments to move along the coastline
10
Sand features
 Spit = a length of accumulated
sand attached to land at one
point
 Tombolos = spits that extend
between two islands or from
one island to the mainland.
 Deltas – form at the mouths of
some rivers.
11
Deltas
 Rivers must carry a lot of sediment
to form a delta
 Usually form in areas with wide
continental shelves, low tidal
change, and mild waves & current.
 Three ways to classify deltas:
 River-dominated deltas = strong
rivers and mild wave and tidal
action
 Tide-dominated deltas = strong
tidal changes
 Wave-dominated deltas = high
wave energy that redistributes river
sediments
12
Barrier Islands
 Barrier islands – sediment deposits that form between the
ocean and the shoreline
 Scientists theorize that barrier islands formed in two ways:
Sand accumulation becoming large enough to form an
island
2. When the sea level rose (millions of years ago), sand dunes
on the shore became islands
1.
 Typical barrier islands have: ocean beach, ocean dunes, a
barrier flat, a salt marsh, and a lagoon
 Storm energy changes barrier islands
13
Coastal Ecosystems
 Rocky shores
 Beaches
 Intertidal (tide pools)
 Estuaries
 Coral Reefs
 Kelp forests
14
Video Notes: Shoreline
 Number your paper from 1-20
 Write down 20 facts from the video.
15