The document summarizes coastal processes and landforms. It discusses how waves, currents, tides, and sea level changes sculpt coastal regions. It also describes various coastal landforms that result from erosion and deposition, including beaches, spits, barrier islands, and lagoons. Coastal zones experience highly energetic conditions due to constant interactions between land, ocean, and atmosphere.

1. Chapter 20: Coastal
Processes and Terrain
McKnight’s Physical Geography:
A Landscape Appreciation,
Tenth Edition, Hess

2. Coastal Processes and Terrain
• The Impact of Waves and Currents on the
Landscape
• Coastal Processes
• Coastal Landforms
2© 2011 Pearson Education, Inc.

3. The Impact of Waves and
Currents on the Landscape
• Coastal processes affect
a tiny portion of Earth’s
landscape
• Waves agents of erosion
• Currents agents of
transportation and
deposition
• Beaches mark transition
between land and water
and are highly variable
3© 2011 Pearson Education, Inc.
Figure 20-4

4. Coastal Processes
• Interface of three major
components of Earth’s
environment
• Highly energetic due to
constant motion of waters
• Importance of wind
• Ocean and lake formations
similar except for:
– Tidal range smaller for lakes
– Water level change differences
– Reefs only in oceanic water
4© 2011 Pearson Education, Inc.
Figure 20-1

5. Coastal Processes
• Waves—transfer of energy through cyclical rising and
falling of a substance
• Most are wind generated over oceans
• Wind stress generated waves, forced waves
• Swells
5© 2011 Pearson Education, Inc.

6. Coastal Processes
• Waves of oscillation and
translation
– Waves that move in a circular
or oscillatory fashion with little
forward movement, waves of
oscillation
– Wave crests and troughs
– Wavelengths and wave heights
– Wave amplitudes
– Shallow water waves influenced
by ocean floor, gain forward
progress, called waves of
translation; wave breaks
6© 2011 Pearson Education, Inc.
Figure 20-2

7. Coastal Processes
• Wave refraction
– Change in wave direction as
they approach shore
– Uneven coastline and irregular
water depth
– Waves bent due to uneven
slowing of waves from irregular
water depth
– Wave action focused on
headlands, much gentler in
adjacent bay areas
7© 2011 Pearson Education, Inc.
Figure 20-5

8. Coastal Processes
• Wave erosion
– Consistent pounding of small
waves results in erosion
– Large storms significantly
enhance coastal erosion
– Air forced into cracks in
coastal rocks when water
moves inland; air released as
water recedes and enhances
erosion
– Chemical action of seawater
– Notches cut in the bases of
cliffs
8© 2011 Pearson Education, Inc.
Figure 20-6

9. Coastal Processes
• Tsunamis
– Waves triggered by disruptions
in ocean floor
– When fault rupture on ocean
floor generates tsunami, entire
depth of ocean above rupture
is displaced
– Inconspicuous in open ocean
with long wavelengths and low
heights
– Can travel over 400 mph
– Significant withdrawal of up to 40
meters before a significant surge
of water 9© 2011 Pearson Education, Inc.
Figure 20-8

10. Coastal Processes
• Tides
– Alterations of ocean level
from gravitational pull of Sun
and Moon
– Two high tides and two low
tides per day
– Topographic effects
generally small
– Significant agents of erosion
only in narrow bays, around
shallow seas, and in
passages between islands
10© 2011 Pearson Education, Inc.
Figure 20-9

11. Coastal Processes
• Changes in sea level and lake level
• Two primary causes of sea level changes
– Rising or sinking of landmass (tectonic change)
– Increase or decrease in amount of ocean water (eustatic
sea-level change)
– Emergent versus submergence land characteristics
• Global warming and sea-level change
– Thermal expansion of water and melting of ice caps increasing
water volume (eustatic)
– Sea level rise of up to 0.5 m by the end of the century
11© 2011 Pearson Education, Inc.

12. Coastal Processes
• Ice push
– Bodies of water that freeze in winter, resulting in expansion
and subsequent contraction
– Ice pushes onto land, significantly modifying land surface,
similar to small glacial advance
– Most common in Arctic and Antarctic regions
12© 2011 Pearson Education, Inc.

13. Coastal Processes
• Organic secretions
– Many aquatic animals form
calcium carbonate shells
– Animals cluster together and
form enormous masses of
reefs, platforms, and atolls
• Stream outflow
– Streams important sources
of sediment to oceans and
lakes
13© 2011 Pearson Education, Inc.
Figure 20-11

14. Coastal Processes
• Currents and coastal
sediment transport
• Longshore currents
– Water moves parallel to
shoreline (“along” shore)
– Develop just offshore and
set up by waves striking
coast at an angle
– Wind direction reflected in
longshore currents
14© 2011 Pearson Education, Inc.
Figure 20-12

15. Coastal Processes
• Currents and coastal
sediment transport (cont.)
• Beach drifting
– Short distance shifting of
sand by breaking waves and
retreating water
– Zigzag pattern of particle
movement downwind and
parallel to coast
– Affects of tides on debris
movement
– Dune formation on coasts
15© 2011 Pearson Education, Inc.
Figure 20-13

16. Coastal Processes
• Coastal deposition
– Results when energy of
moving water is diminished
– Maritime deposits more
ephemeral than noncoastal
deposits due to composition
and lack of vegetative cover
– Sediment budget must be in
balance to allow for deposit
to persist
16© 2011 Pearson Education, Inc.
Figure 20-14

17. Coastal Landforms
• Depositional landforms
• Beaches
– Beaches relatively
homogeneous
– Mark transition between
land and ocean
– Backshore contains berms;
foreshore regularly covered
and uncovered by tides
– Offshore is zone that is
permanently submerged
17© 2011 Pearson Education, Inc.
Figure 20-15

18. Coastal Landforms
• Spits
– At mouth of a bay, sediment
moved into deeper water
– Deposit attached to land at
one end and extends to
open ocean in downcurrent
direction is a spit
– Spits that extend across a
bay, bay barriers or
baymouth bars
– Tombolos: waves converge
on each side and deposit
sand so the bar connects
to land 18© 2011 Pearson Education, Inc.
Figure 20-16

19. Coastal Landforms
• Barrier islands
– Long, narrow sand bar built up
in shallow offshore waters
– Oriented approximately parallel
to shore
– Only rise a few meters above
sea level, but some extend to
great lengths
– Lagoon formation; mudflats
– Life cycle of a lagoon
19© 2011 Pearson Education, Inc.
Figure 20-20

20. Coastal Landforms
• Human modification of
coastal sediment budgets
– Dams act as sediment traps,
allowing less sediment to
reach oceans and resulting
in shrinking beaches
– Use of groins to help impede
the downcurrent flow of
sediment
– Jetties used to keep water
moving and reduce
sediment deposits in
navigation channels
20© 2011 Pearson Education, Inc.
Figure 20-23

21. Coastal Landforms
• Shorelines of submergence
– Most oceanic coastline shows
evidence of submergence at
some time within last 15,000
years
– Ria shorelines
• Submergence results in
drowning of previous river
valleys, producing estuaries
• Coast with numerous estuaries
is called a ria shoreline
21© 2011 Pearson Education, Inc.
Figure 20-25

22. Coastal Landforms
• Shorelines of
submergence (cont.)
– Fjorded coasts
• Extensive glaciation gouges
out troughs by glaciers or ice
sheets
• Troughs far below sea level,
eventually fill with sea water
• Deep coastal indentations are
called fjords
• Create extraordinarily
irregular coastlines
22© 2011 Pearson Education, Inc.
Figure 20-26

23. Coastal Landforms
• Shorelines of emergence and
erosion
– Shoreline features raised well above
current sea level
• Wave-cut cliffs and platforms
– Constant pounding of waves at base
of landforms cuts a notch at the high
water level
– Broad erosional pattern called a
wave-cut bench or wave-cut
platform
– Most cut debris shifted just beyond
wave-cut bench to wave-built terrace
23© 2011 Pearson Education, Inc.
Figure 20-27

24. Coastal Landforms
• Marine terraces
– Wave-cut platforms uplifted
along tectonically rising
coasts
– Several instances of marine
terraces indicate several
episodes of marine terrace
formation
– Can be used to deduce
history of the water levels in
a region
24© 2011 Pearson Education, Inc.
Figure 20-28

25. Coastal Landforms
• Coral coasts
– Most continents and islands fringed with coral reefs or
another coralline structure
– Critical element is a group of anthozoan animals
– Calcium carbonate skeletons from coral polyps
– Have a blossomlike appearance similar to plants
– Have strict requirements for their survival
– Fringing reefs: those built right onto a volcano
– Barrier reefs: coral that appears to float around a volcano
– Atolls
25© 2011 Pearson Education, Inc.

26. Coastal Landforms
• Distribution of coral coasts worldwide
26© 2011 Pearson Education, Inc.Figure 20-29

27. Summary
• Coastal regions make up a very small percentage of
the Earth’s landscape, but have unique structure and
processes
• The coasts are the interface between three of the
four primary spheres of the Earth
• The most energetic coastal processes are observed
by wave motions
• Tsunamis are significant dangerous waves that result
from underwater earthquakes, not from winds
• Tides play a small role in the sculpting of landforms
of coasts
27© 2011 Pearson Education, Inc.

28. Summary
• Numerous processes are involved that modify the
lake level and sea level of bodies of water
• Many other coastal processes, including ice push,
organic secretions, and stream outflow, help
structure coastal landforms
• Currents are primarily responsible for the transport of
coastal sediment
• Coastal deposition takes place in areas where ocean
water moves more slowly, and is typically ephemeral
• The most widespread coastal landform is called a
beach
28© 2011 Pearson Education, Inc.

29. Summary
• Spits and barrier islands result from deposition of
sedimentary material by the longshore currents
• Lagoons result when barrier islands cut off one small
region of ocean water from the remaining ocean
• Humans have modified the structure of shorelines
through damming and the building of groins and
jetties
• Shorelines can be divided into two categories,
emergence or submergence
• Coral coasts consist of organic material and typically
surround volcanoes
29© 2011 Pearson Education, Inc.