Geography
Coastal Landforms
Coastal landforms refer to the various physical features that are found along coastlines, shaped by the processes of erosion, deposition, and weathering. These landforms include beaches, cliffs, spits, and caves, and are constantly evolving due to the actions of waves, tides, and currents. They play a crucial role in protecting coastal areas and providing habitats for diverse ecosystems.
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12 Key excerpts on "Coastal Landforms"
eBook - PDF- Mateo Gutierrez(Author)
- 2012(Publication Date)
- CRC Press(Publisher)
11 COASTAL GEOMORPHOLOGY 1. Introduction 2. Brief history of coastal geomorphology 3. Temporal and spatial scales 4. Sea level variations 5. Waves, currents, and tides 6. Cliff coasts and rocky platforms 7. Coral reef coasts 8. Beaches, barriers, and spits 9. Coastal dunes 10. Mudflats, salt marshes, and mangroves 11. Estuaries and deltas 12. Coastal environments: Uses, management, and risks 11.1 Introduction Bird (2000) defines coastal geomorphology as the study of the evolution of Coastal Landforms, the processes that affect them, and the changes they undergo. These landforms include cliffs, rocky coastal margins, beaches, dunes, estuaries, lagoons, and deltas. The world’s coastal margins are about 100 m wide and 440,000 km long; humans use them for industrial pur- poses, transportation, and recreation. These human activities profoundly impact these areas. The United Nations estimates that 66% of the world’s population lives within a few kilom- eters of the coast (Pethick, 1984). As a result, food produc- tion, communication, cities, and recreational areas all affect the coast. Coasts have significant problems that include flood- ing, erosion, pollution, and sea level variations that require constant attention. Interdisciplinary studies by coastal engi- neers, oceanographers, and geomorphologists have led to significant advances in coastal management (Stephenson and Brander, 2003). In addition, coasts are constantly changing; the change may be catastrophic or imperceptible. Modifica- tions may occur over decades or centuries but they can also take place in a period of hours or minutes. 11.2 Brief history of coastal geomorphology Prior to the 20th century, research on coastal geomorphology was limited to engineering topics related to coastal erosion (Walker and MacGraw, 2005). Charles Darwin made impor- tant observations on coral reefs and the origin of atolls during his famous voyage on the British ship, the Beagle, in 1835 (Shepard, 1959).
eBook - PDF- Timothy Foresman, Alan H. Strahler(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
2. Describe thedepositionallandformsproduced bywaves. 3. Define coastlinesofsubmergence. 4. Explain thefeaturesofcoralreefs. coastline(coast) The zone in which coastal processes op- erate or have a strong influence CoastalLandforms409 by as much as 125 m (410 ft). Rivers cut canyons to depths well below present sea level to reach the ocean. Waves broke against coastlines that are now well underwater. Now that sea level has risen, many coastal landscapes are coastlines of submergence. Still other coastlines are dominated by coral reefs, where ocean waters are warm enough for coral to grow. Erosional Coastal Landforms The breaking of waves against a shoreline provides a va- riety of distinctive features. Where resistant rocks meet the waves, sea cliffs often oc- cur. At the base of a sea cliff is a notch, formed largely by physical weathering. Constant splashing by waves followed by evaporation causes salt crystals to grow in tiny crevices and fissures of the rock, breaking it apart, grain by grain. Hydraulic pressure of waves and abrasion by rock fragments thrust against the cliff also erode the notch. Undercut by the notch, blocks fall from the cliff face into the surf zone. As the cliff erodes, the shoreline gradually retreats shoreward. Sea cliff erosion forms a variety of ero- sional landforms, including sea caves, sea arches, and sea stacks (Figure 13.18). zone in which waves perform their work, as well as the landforms they create. In contrast, the shoreline refers to the dynamic zone of con- tact between water and land. The Earth’s coastlines are enormously varied. For ex- ample, along most of the east coast of the United States, we find a coastal plain gently sloping toward the sea, with shallow lagoons and barrier islands at the coastline. On the west coast, we often find rocky shorelines, with dra- matic sea cliffs, headlands, and pocket beaches. Plate tectonics provides a way to explain these dif- ferences.
eBook - PDF- James Petersen, Dorothy Sack, Robert Gabler, , James Petersen, James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
LEARNING OBJECTIVES WHEN YOU COMPLETE THIS CHAPTER YOU SHOULD BE ABLE TO: 20.1 Sketch the coastal zone, including labels for its principal subdivisions. 20.2 Explain how waves are formed and characterized. 20.3 Discuss how wind waves transfer and deliver energy to the coastal zone. 20.4 Explain why coastlines tend to straighten over time. 20.5 Recount how sediment moves along a beach. 20.6 Identify the three coastal erosion processes and five principal landforms found on erosion-dominated coastlines. 20.7 Describe the types and sources of sediment found in coastal depositional landforms. 20.8 Distinguish between beaches and spits. 20.9 Summarize a global-scale and a regional-scale classification of coasts. 20.10 Differentiate among the three types of coral reef. COASTAL PROCESSES AND LANDFORMS The shorelines of the world are extensive, complex, and often spectacular environments. David Crosbie/Alamy Stock Photo Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 574 C H A P T E R 2 0 • C O A S T A L P R O C E S S E S A N D L A N D F O R M S 20-1 The Coastal Zone Most of the processes and landforms of the marine coastal zone are also found along the coastlines of large lakes. All are consid- ered standing bodies of water because the water in each occupies a basin and has an approximately uniform still-water level around the basin. This contrasts with the sloping, channelized flow toward lower elevations that constitutes streams. The shoreline of a standing body of water is the exact and constantly changing contact between the ocean or lake surface and dry land.
eBook - PDF- Tom Garrison, Robert Ellis(Authors)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 153 8 Coasts KEY CONCEPTS The location of a coast depends on global tectonic activity and the ocean’s water volume. The shape of a coast is a product of uplift and subsid-ence, the wearing down of land by erosion, and the redistribution of material by sediment transport and deposition. Coasts may be classified as erosional coasts (on which erosion dominates) or depositional coasts (on which deposition dominates). Beaches change shape and volume as a function of wave energy and the balance of sediment input and removal. Human interference with coastal processes has generally accelerated the erosion of coasts near inhabited areas. Coasts are places of rapid change, tenacious organisms and often great beauty. The northern California coastline along Big Sur is a stunning example of the complexity that can occur at the land and sea interface. Lynn Y/Shutterstock.com Post-Glacial Sea Level Rise 20 18 0 12 6 0 14 8 4 16 10 2 Thousands of years ago 00 50 50 25 75 75 Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 CHAPTER 8 154 8.1 Coasts Are Shaped by Marine and Terrestrial Processes Coastal areas join land and sea. Our personal experience with the ocean usually begins at the coast. Have you ever wondered why a coast is shaped as you see it? These temporary, often beautiful junctions of land and sea are subject to rearrange-ment by waves and tides, by gradual changes in sea level, by biological processes, and by tectonic activity. The place where ocean meets land is usually called the shore , and the term coast refers to the larger zone affected by the processes that occur at this boundary.
eBook - PDFOceanography
An Invitation to Marine Science
- Tom Garrison(Author)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. CHAPTER 12 336 12.1 Coasts Are Shaped by Marine and Terrestrial Processes Coastal areas join land and sea. Our personal experience with the ocean usually begins at the coast. Have you ever wondered why a coast is in a particular location or why it is shaped as you see it? These temporary, often beautiful junctions of land and sea are subject to rearrangement by waves and tides, by gradual changes in sea level, by biological processes, and by tectonic activity. The place where ocean meets land is usually called the shore , and the term coast refers to the larger zone affected by the processes that occur at this boundary. A sandy beach might form the shore in an area, but the coast (or coastal zone) includes the marshes, sand dunes, and cliffs just inland of the beach, as well as the sandbars and troughs immediately offshore. The world ocean is bounded by about 1,000,000 kilometers (620,000 miles) of shore, about one third of which are sandy beaches (Figure 12.1) . Because of its proximity to both ocean and land, a coast is subject to natural events and processes common to both realms. A coast is an active place. Here is the battleground on which wind waves break and expend their energy. Tides sweep water on and off the rim of land, rivers drop most of their sediments at the coasts, and ocean storms pound the continents. The location of a coast depends primarily on global tectonic activity and the volume of water in the ocean. The shape of a coast is a product of many processes: uplift and subsidence, the wearing down of land by erosion , and the redistribution of material by sediment transport and deposition.
eBook - PDF- Alan F. Arbogast(Author)
- 2017(Publication Date)
- Wiley(Publisher)
If the top of the arch collapses, an isolated sea stack remains, such as the one to the left. Note the tilted rock strata. 450 CHAPTER 19 Coastal Processes and Landforms Depositional Coastlines We have just seen how coastlines are shaped by erosion and some of the diagnostic landforms that result from this process. Now, let’s turn to the Coastal Landforms created when sediment is deposited in various ways and places. You were briefly intro- duced to this concept with the formation of a pocket beach be- tween two eroding headlands (Figure 19.14c). Coastlines in the process of extending outward into the water through deposi- tion are said to be undergoing progradation. Beaches The part of the coastal landscape people are probably most familiar with is the beach. Beaches are dynamic places where sediment is deposited through the combination of waves, beach drift, and wind. In some places, beaches are supplied with alluvial sands derived from land far inland. The beach is a transition between the water and the landmass and consists of exposed, unconsolidated sediments that usually range from sand to cobbles. Although finer silt and clay-sized particles are sometimes contained within a beach, they are usually carried away in suspension by the longshore current. Most beach growth occurs during the summer months in the Northern Hemisphere when the weather is relatively calm. In winter, however, beaches can be significantly eroded due to large waves created by strong storms. If you happen to live on or near a beach, notice how the shape of the beach can change between seasons. Figure 19.21 shows how beach components are differenti- ated on the basis of their relative position to the water. The offshore is permanently submerged and is the zone where waves break and the surf is most active.
No longer available |Learn more- James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2016(Publication Date)
- Cengage Learning EMEA(Publisher)
(c) A sea arch in Alaska. (d) Sea stacks along a cliffed coast. (a) D.Sack (b) Jim Petersen (c) NOAA Image Library (d) Richard Price/The Image Bank/Getty Images Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. C O A S T A L G E O M O R P H I C P R O C E S S E S 583 beach materials (● Fig. 20.19). Sand-sized sediment eroded from the beach in winter forms a deposit called a longshore bar that lies submerged parallel to shore, with the sediment returning to the beach in summer. On the Atlantic and Gulf coasts of the United States, the late summer to early fall hurricane season is also a time when beach erosion can be severe. Whereas beaches are attached to the mainland along their entire length, spits are coastal depositional landforms connected to the mainland at just one end (● Fig. 20.20). Spits project out into the water like peninsulas of sediment. They form where the main- land curves significantly inland while the trend of the longshore current remains at the original orientation. Sediments accumulate into a spit in the direction of the longshore current (● Fig. 20.21a). Where similar processes form a strip of sediment connecting the mainland to an island, the landform is a tombolo (Fig. 20.21b). Another category of Coastal Landforms are barrier beaches, elongated depositional features constructed parallel to the main- land. Barrier beaches act to protect the mainland from direct wave attack. All barrier beaches have restricted waterways, called lagoons, that lie between them and the mainland.
eBook - PDFPhysical Geography
Great Systems and Global Environments
- William M. Marsh, Martin M. Kaufman(Authors)
- 2012(Publication Date)
- Cambridge University Press(Publisher)
Differences in geography will be extremely important because certain countries, Bangladesh, for example, are limited to coastal lowlands, while others have only modest exposure to the sea and/ or their coasts and settlements lie at higher elevations. And, of course, national wealth will be significant, especially when we consider that over 95 percent of the people added to the planet in the twenty-first century will live in less-developed countries where costly adaptations will be impossible to under- write. Finally, how we plan and design our land-use facilities in the future will be critically important. If we resist the rigid, single-minded approaches of the past and instead build resilience in our coastal land-use systems, that is to say, incorporate flexibility and readiness into our land-use systems, humanity on the world’s coasts may fare reasonably well. Kobe, Japan is not unlike large coastal cities across the world, with development pushing its way into the sea. 583 Chapter Summary Summary and Overview Coastal Systems: Waves, Currents, and Landforms Some of the most interesting and meaningful geographic questions concern edge environments, and few if any rank higher than coastlines. As geomorphic systems, those of the coast are powerful and dynamic, for in the expanse of a lifetime or less it is possible to witness major geographic changes on the edges of landmasses large and small. And it appears that the magnitude and frequency of change are increasing with changes in the atmospheric energy, sea level, and land use. Once again we are reminded of the interconnected nature of geographic phenomena, not only in present times, but, as the summary diagram suggests, over the long term as well.
eBook - PDF- Alan H. Strahler(Author)
- 2013(Publication Date)
- Wiley(Publisher)
Marine terraces are common along the continental and island coasts of the Pacific Ocean, where tectonic processes are active along the mountain and island arcs. DEPOSITIONAL Coastal Landforms Most of the sediment we find along a coastline is provided by rivers that reach the ocean. Waves then transport and deposit this sediment to take shape as shoreline features such as beaches, bars, and spits. These depositional landforms are relatively transitory, how- ever, appearing, disappearing, or migrating as a result of seasonal changes, storms, and human engineering. Beaches A beach is a wedge-shaped sedimentary deposit, usually of sand, built and worked by wave action. The face of a beach varies over time as waves either deposit or erode more sand. During short periods of storm activity, waves cut back the beach, giving it a long, flat, sloping profile. The sand moves just offshore and along the shore via longshore drift. Gentler waves return the sand to the beach, building a steeper beach face and a bench of sand at the top of it. When sand leaves a section of beach more rap- idly than it is brought in, the beach is narrowed and the shoreline moves landward. Conversely, when sand arrives at a particular section of the beach more rap- idly than it is carried away, the beach is widened and Waves erode weak materials, resulting in marine scarps, and weather resistant rocks, which are reshaped as marine cliffs. Caves, arches, stacks, and abra- sion platforms are land- forms of marine cliffs. University of Washington Libraries, Special Collections, John Shelton Collection, KC8974 Marine terrace Former sea level Former sea cliff 16.17 Marine terraces Marine terraces give us a visual record of coastlines and sea levels from the Earth’ s past. UPLIFT FORMS A TERRACE After a period of tectonic uplift or lowered sea level, the shore platform at the base of the cliffs is raised up to become a marine terrace.
eBook - PDF- James Petersen, Dorothy Sack, Robert Gabler, , James Petersen, Dorothy Sack, Robert Gabler(Authors)
- 2014(Publication Date)
- Cengage Learning EMEA(Publisher)
Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 461 C O A S T A L D E P O S I T I O N (a) (b) (c) (d) (e) ■ FIGURE 17.14 Examples of landforms created by wave erosion. (a) A notch exposed near the base of basaltic sea cliffs in Hawaii. (b) A sea cave carved in limestone along Italy’s Mediterranean Sea coast. (c) A sea arch in Alaska. (d) An abrasion platform carved on steeply dipping sedimentary rocks, central California, partially exposed at low tide. (e) A marine terrace, the wide, beveled plain atop this eroding coastline. What other coastal erosional landforms do you see in photo (e)? D. Sack D. Sack J. Petersen Robert Cameron/Getty Images NOAA Image Library Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. C H A P T E R 1 7 • C O A S TA L P R O C E S S E S A N D L A N D F O R M S 462 Coastal Depositional Landforms The most common landform of coastal deposition is the beach , a wave-deposited feature that is contiguous with the mainland throughout its length ( ■ Fig. 17.15). Many beaches are sandy, but beaches of other grain sizes are also common, as for example, the cobble beach discussed earlier in the sec-tion on coastal erosion. In settings with high wave energy, particles tend to be larger and beaches steeper than where wave energy is low. Beach sediments come in a variety of col-ors depending on the rock and mineral types represented. Tan quartz, black basalt, white coral, and even green olivine beaches exist on Earth.
eBook - PDF- Vijay K. Sharma(Author)
- 2010(Publication Date)
- CRC Press(Publisher)
Inman and Nordstrom (1971) proposed a geophysical classification of coasts based on the concept of plate tectonics , suggesting that the nature of interaction between continental and oceanic plates at plate boundaries evolves morphologically distinct collision, trailing edge, and marginal coasts, and their subtypes. Collision coasts occur along the subduction zone of plate interaction, trailing edge coasts align with the trailing edge of continental plates, and marginal coasts occur along oceanic plates facing island arcs. Davies (1980) recognized that latitude-dependent storm, swell, and protected wave environments strongly affect the contemporary morphology of coasts (Figure 11.28). The storm wave environment of mid-latitude coasts is typically associated with shin-gle beaches, wide shore platforms, and sea cliffs. The east and west coast swell envi-ronment at tropical latitudes develops sandy beaches, and coasts commonly devoid of sea cliffs and shore platforms. The protected wave environment at high latitudes, Storm wave environments Protected sea environments West coast swell environments East coast swell environments Trade and monsoon influences Tropical cyclone influences FIGURE 11.28 Major global wave environments for the classification of coasts. (Source: Figure 27 in Davies, J. L., Geographical Variation in Coastal Development [Edinburgh: Oliver & Boyd, 1980]. With permission from Addison Wesley Longman.) Coastal Processes and Landforms 337 and along bays, estuaries, and enclosed seas, is commonly reflected in the domi-nance of mud beaches and the near absence of shore platforms along coasts. COAST OF INDIA Nearly 5,700 km of coast of India, including that of the Andaman and Nicobar Islands in the Bay of Bengal and Lakshadweep Islands in the Arabian Sea, is diverse in morphology, evolution, and chronology (Vaidyanadhan, 1987). The east coast, in general, has prograded into the Bay of Bengal over a subsiding continental shelf.
eBook - PDFPhysical Geography
Made Simple
- Richard H. Bryant(Author)
- 2013(Publication Date)
- Made Simple(Publisher)
Johnson's is a simple genetic classification, but places heavy emphasis on one factor, sea-level change, and requires that we know something about the past history of the coastline. Strictly speaking, nearly all shorelines are com-pound. A more recent and potentially much more useful scheme is that proposed by J. L. Davies on the basis of energy environments. On a world map (Fig. 8.10) he recognises (a) storm wave environments, where destructive storm breakers are frequent and shingle beaches are common; (b) swell environments, which are characterised by flat constructional waves; and (c) protected environments, the low-energy conditions of enclosed or partially Coastal Features 95 Storm wave environments | ·* I Swell environments (West coast) | |Protected sea environments ) *· [Swell environments (East coast) Fig. 8.10. A classification of coastlines according to energy characteristics. (After J. L. Davies, courtesy Longman) enclosed seas. It is also possible to apply the concept of differing energy environments on a more local scale, as has been illustrated with some of the features described in this chapter. Suggested Further Reading Bird, E. C. F., Coasts (3rd edn.), Australian National University Press, Canberra, 1984. Bird, E. C. F., Coastline Changes: A Global Review, Wiley, Chichester, 1985. Davies, J. L., Geographical Variation in Coastal Development, Oliver & Boyd, Edin-burgh, 1972. King, C. A. M., Beaches and Coasts (2nd edn.), Arnold, London, 1972. Pethick, J. S., An Introduction to Coastal Geomorphology, Edward Arnold, London, 1984. CHAPTER NINE LANDSCAPE DEVELOPMENT Our consideration of geomorphology in this section of the book has been largely concerned with an understanding of contemporary processes and the resulting forms. But we have also seen that some landforms may retain the imprint of past processes, and in this chapter we examine the historical factor in more detail.
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