Shorelines Lecture 15 PDF

.:- -,.. ,, l! e F •. " • F • What is Shoreline? ► the line that marks the contact between land and sea. ► When it comes to the deposition of sediment, they are transition zones between marine and continental environments. ► Interface - a common boundary where different parts of a system in...

.:- -,.. ,, l! e F •. " • F • What is Shoreline? ► the line that marks the contact between land and sea. ► When it comes to the deposition of sediment, they are transition zones between marine and continental environments. ► Interface - a common boundary where different parts of a system interact. Source: https://www.billsphotooftheda y.com/February_27_2014/ HDA. Reyes I Principles of Geology • Coastal Zone ► The coastal zone consists of several parts. The beach is an accumulation of sediment on the landward margin of the ocean or a lake. It can be thought of as material in transit along the shore. Low-tide shoreline Shoreline l~ High-tide Berm •hor~e -~ Coastline Dunes J. l ' I • I \ ' '' ' - - - - . - -\------- -------- -i l~---I - ~ ~ - - - - -, I - face I ,---I : ~---+---------~:'- -------~ I 1 - - - - -Foreshore------- - - -Backshore- - -1 I I - - - Offsho r e - - - ' -Nearshore-1 1 ' I Beach ----------------1 ~ ' S h o r e - - - - -- '- - - C o a s t - -- I HDA. Reyes I I I Principles of Geology • Coastal Zone ► Shore - the area that extends between the lowest tide level and the highest elevation on land that is affected by storm waves. Low-tide shoreline Shoreline l~ High-tide Berm Coastline l J. •hor~e -~ ' Dunes I • I \ ''' ' ' - -- - - r - -· \------- l~- --- -------- -iI I Offsho r e - - -:I face I ' ,---I I Beach _ _...----------,1 ~ : ~~--+-~~-~___.:'- -__.------I ---- -foreshore- ------ - - -Backshore- - -1 Nearshore--• , - - - C o a s t - -I -------Sho I r e - - - - -- .. 1 1 HDA. Reyes I Principles of Geology l • Coastal Zone ► Coast - extends inland from the shore as far as ocean-related features can be found. Low-tide shoreline Shoreline l~ High-tide Berm • hor~e -~ Coastline Dunes J. l ' I • I \ '' - -- - - r - -· \------- ------ _ _...----------,1 . - - - -r- l\.....- --- 1 1 : ~ '' ' ' ,---I I Beach face : 1,_ __ _ . - - - - - - - ~-~'- ------_., -----Foreshore------:- - -Backshore- - -r - - - - - - - 1 - - - - Offs h o r e - - - 1 -Nearshore-1- - - - - - - S h o r e - - - - - - - -a.--- - - C o a s t - - l I HDA. Reyes I Principles of Geology • Coastal Zone ► Foreshores - the area exposed when the tide is out (low tide) and submerged when the tide is in (high tide). Low-tide shoreline Shoreline l~ High-tide Berm Coastline l J. •hor~e -~ ' Dunes I • I \ '' - -- - - r - -· \------- l\.....- --- -------- -i - - - - - - -, _ _...----------,1 ' ' ,---I I Beach : I face , _ _ _ _ _ _ _ _, ______.--~:'- - _ _ . - - - - - - I :-1 --Foreshore------J:---Backshore---: ----Offshore---1-Nearshore-1 1 ~ '' I HDA. Reyes Shore------'---Coast--- I Principles of Geology • Coastal Zone ► Backshores - landward of the high-tide shoreline. ► It is usually dry, being affected by waves only during storms. Low-tide shoreline Shoreline l~ High-tide Berm •hor~e -~ l Coastline Dunes J. 'I • I \ '' '' ' '-~i------ -------- -i l~- --- ----------, Beach face I I 1 - ~ ~ - - - - -: -----Foreshore-------t:---Backshore---: 1 ----Offshore---'-Nearshore-1 1 1 Shore------'---Coast--- I HDA. Reyes I I Principles of Geology • Coastal Zone ► Nearshores - lies between the low-tide shoreline and the line where waves break at low tide. Low-tide shoreline Shoreline l~ High-tide Berm •hor~e -~ Coastline Dunes J. l ' I • I \ '' - -- - - r - -· \------- l\.....- --- -------- -i ' ' ,---I I Beach _ _...----------,1 ~ '' : face ~ -~ - ~ - - - ~ ~:'- - _ _ . - - - - - - - I I 1 -----Foreshore------- - - -Backshore- - -1 - - - - Offshore--- .. l ·""'" :- - -N-.e-ars _h_o_re--- 1 ...:.. . HDA. Reyes S h ~ r e - - - - - -:- - - C o a s t - - - I Principles of Geology • Coastal Zone ► Of/shores - Seaward of the nearshore zone. Low-tide shoreline Shoreline l~ High-tide Berm Coastline l J. •hor~e -~ ' Dunes I • I \ '' - -- - - . - -\------- l~--- - - -- -------- -iI - - - - - ~ -, ----------------1 ~ '' ' ' ,---I I Beach : face ~ -~ - ~ - - - ~ ~:'- -___.------I 1 1-----Foreshore--- ---Backshore---1 I - - - - O f f s h o r e - - - -ll - -Nearshore-: HDA. Reyes Sh~re------:---Coast--- I Principles of Geology • Coastal Zone ► Beach - an accumulation of sediment found along the landward margin of the ocean or a lake. Low-tide shoreline Shoreline High-tide shoreline Berm Coastline Dunes . I • I \ '' ' l~- ---------i --I - - - - - - -, I - •~i--- ----------------1 I ' I I Beach : ra_c_e~==-~----.....;;~ : 1 ----"------ .___ I 1 1 - - - - -Foreshore------- - - -Backshore- - I I I - - - Offsho r e - - - ' -Nearshore-1 1 __,., '' I HDA. Reyes S h o r e - - - - -- '- - - C o a s t - -- I Principles of Geology • Coastal Zone ► Berm - are relatively flat platforms often composed of sand that are adjacent to coastal dunes or cliffs and marked by a change in slope at the seaward Low-tide shoreline Shoreline !~ r;:l High-tide shor Coastline Dunes W .l . e ' I • I \ ' '' ' - - - - . - -\------- -------- -i l~---I - ~ ~ - - - - -, I face I ,---I : ~---+---------~:'- -------~ I 1 -----Foreshore------- ---Backshore---1 I I ----Offshore---'-Nearshore-1 1 ' I Beach ----------------1 ~ ' Shore------'---Coast--- I HDA. Reyes I I I Principles of Geology • Coastal Zone ► Beach face -is the wet sloping surface that extends from the berm to the shoreline. Low-tide shoreline Shoreline l~ High-tide Berm Coastline l J •hor~e -~ Dunes '. I •I \ '' ~-,---iiiiiiiii'"- i r - -· \------ ______-- -i l~- --I - - - - - - -, I - _ _...----------,1 I ' ' ,---I I Beach : face :,_ ___.------- I 1 1 - - - - -Foreshore------- - - -Backshore- - I I I - - - Offsho r e - - - ' -Nearshore-1 1 ~ '' I HDA. Reyes S h o r e - - - - -- '- - - C o a s t - -- I Principles of Geology • Waves ► Ocean Waves -energy traveling along the interface between ocean and atmosphere, often transferring energy from a storm far out at sea over distances of several thousand kilometers. Source: https://gfycat. com/gifsfsearch /big+wave HDA. Reyes I Principles of Geology • Waves ► Crest - The tops of the waves ► Trough - The bottom of waves Crest Crest Trough ,- - - - Wavelength - - --, G ---- ____-:::::::::::::1~~~:::::-: ____ ------------------------- ----- ------, -----Water - - - particle motion Still water level , ,, ,, ' Neghgible water movement below 1/2 wavelength FIGURE 13.5 This diagram illustrates the basic parts of a wave as well as the movement of water particles wit h the passage of the wave. Negligible water movement occurs below a depth equal to one half the wavelen~th (the level of the dashed line). HDA. Reyes I Principles of Geology ,, • Waves ► Still water level - Halfway between the crests and troughs ► The level the water would occupy if there were no waves. Crest Crest Trough Crest Trough ,- - - - Wavelength- - --, ---- -----====~::::::::1~~~~~=====-=---- ------------------------- ----- Water - - particle motion -----r ----- ___ Still water .._ level , _. ,, , ,, Neghgible water movement below 1/2 wavelength FIGURE 13.5 This diagram illustrates the basic parts of a wave as well as the movement of water particles with the passage of the wave. Negligible water movement occurs below a depth equal to one half the wavelen~th (the level of the dashed line). HDA. Reyes I Principles of Geology ,, • Waves ► Wave height - The vertical distance between trough and crest Crest Crest Trough Crest Trough ,- - - - Wavelength - - --, - Water - - particle motion , ,, ,, ' Neghgible water movement below 1/2 wavelength FIGURE 13.5 This diagram illustrates the basic parts of a wave as well as the movement of water particles with the passage of the wave. Negligible water movement occurs below a depth equal to one half the wavelen~th (the level of the dashed line). HDA. Reyes I Principles of Geology ,, • Waves ► Wavelength - the horizontal distance between successive crests (or troughs) Crest Crest Crest Trough ---- ____-:::::::::::::1~~~:::::- _____ ------------------------- ----- ------, -----Still Water - - - particle motion water level , ,, ,, ' Neghgible water movement below 1/2 wavelength FIGURE 13.5 This diagram illustrates the basic parts of a wave as well as the movement of water particles wit h the passage of the wave. Negligible water movement occurs below a depth equal to one half the wavelen~th (the level of the dashed line). HDA. Reyes I Principles of Geology ,, • Waves ► Wave period - The time it takes one full wave-one wavelength-to pass a fixed position Crest Crest Crest Trough ---- ____-:::::::::::::1~~~:::::- _____ ------------------------- ----- ------, -----Water - - - particle motion Still water level , ,, ,, ' Neghgible water movement below 1/2 wavelength FIGURE 13.5 This diagram illustrates the basic parts of a wave as well as the movement of water particles wit h the passage of the wave. Negligible water movement occurs below a depth equal to one half the wavelen~th (the level of the dashed line). HDA. Reyes I Principles of Geology ,, • Waves ► Factors affecting the height., length., and period of waves ✓ Wind speed ✓ Length of time the wind has blown ✓ Fetch - the distance that the wind has travelled across the open water. I' c- .... .... ....... ...... J.. ...... '!' ~ f' ... ~ ... \ott...... . .. ,,.. J f .. ,. .. HDA. Reyes Source: https;//www.roleplaygateway. com/ro/ep/ay/the-infinityrealm I Principles of Geology • Waves ► Whitecaps - ocean breakers formed when critical point is reached where waves grow so tall that they topple over. Source; https;//www. sh utte rstock. co m/video/c /ip-645 7163-ocea n-waves-wh ite-caps-/a rg e HDA. Reyes I Principles of Geology • Waves ► Swells - lower in height and longer in length and may carry the storm's energy to distant shores when wind changes its direction relative to wave direction. Source: https;///earntosur fkona.com/featur ed/learndifferencegroundswe/1-vswind-swell/ HDA. Reyes I Principles of Geology • Waves ► Circular Orbit Motion - As the wave travels, the water passes the energy along by moving in a circle ► Observation of an object floating in waves reveals that it moves not only up and down but also slightly forward and backward with each successive wave. ► The energy contributed by the wind to the water is transmitted not only along the surface of the sea but also downward. FIGURE 12 6 The mcM:mi<!'Cs of ~c tD'f DOA1 lll>OW the the w.wi:, i:,..., 11d-e but th,, wa•er HDA. Reyes I Principles of Geology doe, nae advance aopr=alv from Its ongin:,l ~ In d,j5 ~~ th,, w..., move, Fram left to right o• u,e toy boat I.and ~e 'Nllll.e" whlcli It ,s ll<a-;,t1ng, -o.~h:,~ ,nan =:>ginc:ryor,c;ac. • Waves ► Surf Zone - As a wave advances toward the shore, the slightly fa ster waves farther out to sea catch up, decreasing the wavelength. As the speed and length of the wave diminish, the wave steadily grows higher. Finally, a critical point is reached when the wave is too steep to support itself and the wave front collapses, or breaks, causing water to advance up the shore. r I Deep waler - AppruaGhi11g shore - waves with constant-------.~waves touch bottom wavelength (wavelength decreases) I S rf ~ __,,,- U zone (breakers form) - - - - -~-- - --~--~-1 ~~~~ Depth is >112 wavelength ------ ------- I• HDA. Reyes Velocity dE!?reases {wave height increases) I Principles of Geology •I • Waves ► Surf- The turbulent water created by breaking waves ► Swash - turbulent sheet of water from collaps ing breakers ► Backwash - water flowing back down to the beach toward the surf zone Source: https://giphy.com /gifs/cinemagraph -cinemagraphs/4hLyOGRJWNSR8 QQB HDA. Reyes I Principles of Geology • Wave Refraction ► The bending of waves ► Plays an important part in shoreline processes ► Wave impact is concentrated against the sides and ends of headlands that project into the water, whereas wave attack is weakened in bays. wavo Rofr.icllon Source: https://m ediap/ayer.p earsoncmg. com/assets/r6ziBjD6eZimrAoc5jJEJ2 L6 O_ GyG4Qz HDA. Reyes Source: http://www.bcsnoticias.mx/rechazan-que-mortadad-de-tortugas-y-lobosmarinos-en-san-juanico -sea-por-minera-2/ I Principles of Geology • Longshore Transport Netmowmant • of .sand •• ► Beach grulns The effect of swash and backwash pattern of water movement is to transport particles of sediment 1n a zigzag pattern along the beach face drift FIGURE 13.11 Beach dnft and longshore currents are created by obliquely breaking wave5 Beach drift occurs as incoming waves carry sand obliquely up the beach, while the water from spent waves carries it directly down the slope of the beach. Similar movements occur offshore 1n the surf zone to create the longshore current These processes transport large quantities of material along the beach and m the surf zone. In the photo, waves approaching che beach at a slight angle near Oceanside, California, produce a longshore current moving from left to right. (Photo by John S. Shelton) HDA. Reyes I Principles of Geology • Longshore Transport Netmowmant • of .sand •• ► Longshore grulns Current- an ocean current that moves parallel to shore. It is caused by large swel Is sweeping into the shoreline at an angle and pushing water down the length of the beach in one direction FIGURE 13.11 Beach dnft and longshore currents are created by obliquely breaking wave5 Beach drift occurs as incoming waves carry sand obliquely up the beach, while the water from spent waves carries it directly down the slope of the beach. Similar movements occur offshore 1n the surf zone to create the longshore current These processes transport large quantities of material along the beach and m the surf zone. In the photo, waves approaching che beach at a slight angle near Oceanside, California, produce a longshore current moving from left to right. (Photo by John S. Shelton) HDA. Reyes I Principles of Geology • Rip Currents ► Concentrated movements of water that flow in the opposite direction from b rea king waves. ► Most of the back-wash from spent waves finds its way back to the open ocean as an unconfined flow across the ocean bottom called sheet/low. ► The best strategy for exiting a rip current is to swim para lie I to the sh ore for a Source: https://www.britannica.com/science/rip-current few tens of meters. HDA. Reyes I Principles of Geology • Shoreline Features ► Erosional Features □ Wave-cut cliffs originate due to the cutting action of the surf against the base of .... ,... coastal land. Source:http://geo/ogycafe.com/oceans/chapter12. html HDA. Reyes I Principles of Geology • Shoreline Features ► Erosional Features □ Wave-cut platform benchlike surface left behind by the receding cliff. □ The platform broadens as wave attack continues Source:http://geo/ogycafe.com/oceans/chapter12. html HDA. Reyes I Principles of Geology • Shoreline Features ► Erosional Features □ Marine Terraces - If a wave-cut platform is uplifted above sea level by tectonic forces. □ Marine terraces are easily recognized by their gentle seaward-sloping shape and are often desirable sites for coastal roads, buildings, or agriculture. HDA. Reyes I Principles of Geology • Shoreline Features ► Erosional Features □ Sea Cave- First to form when wave erodes headlands forming a concave figure. Source; https;//pt. depositpho tos. com/28319223/stock-ph oto-sea-caves-on-marathonisiislan d. html HDA. Reyes I Principles of Geology • Shoreline Features ► Erosional Features □ Sea Arches- Formed when two caves on opposite sides of a headland unite Source; https;//www. telegraph. co. uk/travel/lists/beautiful-sea-arc hes-you-mustvisit/mallorca/ HDA. Reyes I Principles of Geology • Shoreline Features ► Erosional Features □ Sea Stack- Eventually, when the arch fall, it will leave th is isolated remnant. Source: https;// bugaga. ru/ interesting/1 146733146-samye-znam en itye-mo rskieskaly.html HDA. Reyes I Principles of Geology • Shoreline Features ► Depositional Features □ Spit - an elongated ridge of sand that projects from the land into the mouth of an adjacent bay □ Often the end in the water hooks landward in response to the dominant direction of the /ongshore current HDA. Reyes I Principles of Geology • Shoreline Features ► Depositional Features □ Baymouth Bar - a sandbar that completely crosses a bay, sealing it off from the open ocean. □ Such a feature tends to form across bays where currents are weak, allowing a spit to extend to the other side. ~ 2004 Tlw111~11 • e ,uuks/Cu!t., Source: http:// www. writeopinions. com/b aymouth-bar HDA. Reyes I Principles of Geology • Shoreline Features ► Depositional Features □ Tombola - ridge of sand that connects an island to the mainland or to another island, forms 1n much the same manner as a spit. Source:https://www.researchgate.net/figure/210-Tomb o/o-of-/so /a-Bel/a-northof-Capo-Taormina-Co urtesy-Geostudies_fig6_290443671 HDA. Reyes I Principles of Geology • Shoreline Features ► Depositional Features □ Isthmus - a narrow strip of land with sea on either side, forming a link between two larger areas of land. Source: https://www. earthmagazin e. org/artic/e/panamas-isthm us-stays-3-million-years-yo ungfurther-eviden ce-needed-suppo rt-o/der-age HDA. Reyes I Principles of Geology • Shoreline Features ► Depositional Features □ Barrier Islands These low ridges of sand parallel the coast at distances from 3 to 30 kilometers offshore. Florida Source: https;//www.tripstodiscover.com/barrier-islands-in-florida/ HDA. Reyes I Principles of Geology • Hurricanes ► The whirling tropical cyclones that occasionally have wind speeds exceeding 300 kilometers per hour (United State) ► In the western Pacific they are called typhoons, and in the Indian Ocean they are sim I called c clones Source: https://www.theonion.com /how-hurricanes-form1819594194 HDA. Reyes I Principles of Geology • Hurricanes ► Most hurricanes form between the latitudes of 5 degrees and 20 degrees over all the tropical oceans except those of the South Atlantic and eastern South Pacific ► The North Pacific has the greatest number of storms, averaging 20 per year. £:Qua.tor HDA. Reyes I Principles of Geology • Coast ► Emergent Coast develop either because an area experiences uplift or as a result of a drop in sea level. ► Limd Active beach - Exoo&od rises ........____ /;;;;,::~cut , ~ Sea level in tho past Activs baac:r / ~--- ..__ l imo [a) Emo,go.t>t 00t.1sts Wr;.vc oro$10 r"I producoc .a vva'l(t cut bor"lch alo,,o al"l omc,gor'\t 000$1 As tho land rises, the borlch bccomo!'; 3 ttfllrll,;ff, i-Jrld iJ rli;IW WilVt:1--<.;tJl lHmt;h fonna, Rising land or a falling water level exposes wave-cut cliffs and platforms above sea level. lb) Submergant cossts: A coast oefore sea level rises Rivers d'ein va'leys and deposit sediment or a coasta plain f,,s a subrnergent coast fornns. &ca level nsos and f oocs tho valleys, and waves orodo tho headlands Source: http://geo/ogy/eam. biogspot. com/2015/12/causes-of-coastal-variability. htm I HDA. Reyes I Principles of Geology NO'M ::/4..~bench /wave-cut • Coast ► Submergent Coast created when sea level rises or the land adjacent to the sea subsides. ► Shorelines that have been submerged the relatively recent past are often highly irregular because the sea typically floods the lower reaches of river valleys flowing into the ocean. drowned ► Estuaries river mouths - Exoo&od Limd Active beach rises._ /;;;;,::~cut , ~ ........_ Sea level Activs baac:r in the past / ~--- ..__ l imo [a) Emo,go.t>t 00t.1sts Wr;.vc oro$10 r"I producoc .a vva'l(t cut bor"lch alo,,o al"l omc,gor'\t 000$1 As tho land rises, the borlch bccomo!'; 3 ttfllrll,;ff, i-Jrld iJ rli;IW WilVt:1--<.;tJl lHmt;h fonna, lb) Submergant cossts: A coast oefore sea level rises Rivers d'ein va'leys and deposit sediment or a coasta plain f,,s a subrnergent coast fornns. &ca level nsos and f oocs tho valleys, and waves orodo tho headlands Source: http://geo/ogy/eam. biogspot. com/2015/12/causes-of-coastal-variability. html HDA. Reyes I Principles of Geology NO'M ::/4..~bench /wave-cut • Tides ► daily changes in the elevation of the ocean surface Combined gravitational pull of the Sun and the Moon ,, , , , , ~ , , .. -- __ L __ _ ~ -... ... ~ ... ' '' ' \ \ I \ Low Tide , \ .. Moon 'I High Tide I I High Tide I I f '' I I Low Tide \ I @ Source: https://www.timeanddate.com/astronomy/moon/tides.html HDA. Reyes I Principles of Geology limeanddate.com • Tides I I ► Spring Tides - have no connection with the spring season but occur twice a month during the time when the Earth-Moon-Sun system is aligned. Ne.vmoon A. Spring tide ► Produces larger tidal bulges (higher high tides) and deeper tidal troughs (lower low tides), producing a large tidal range. ,; ,, Fntquarter moon I I I Solar ode ' , / I ToSm -----¢ I I ' \ \ ' B. Neaptide HDA. Reyes I Principles of Geology lunar tide • Tides I I ► Neap Tides - occur twice each month. Each month, then, there are two spring tides and two neap tides, each about one week apart ► Ne.vmoon A. Spring tide The gravitational forces of the Moon and Sun act on Earth at right angles, and each partially offsets the influence of the other ,; ,, Fntquarter moon I I I Solar ode ' , / I ToSm -----¢ I I ' \ \ ' B. Neaptide HDA. Reyes I Principles of Geology lunar tide • Tidal Current ► The term used to describe the horizontal flow of water accompanying the rise and fall of the tide. ► These water movements induced by tidal forces can be important in some coastal areas. High Tide ----------- T•"l"''' □ Flood currents Tidal currents that advance into the coastal zone as the tide nses □ Ebb current seawardmoving water HDA. Reyes Low Tide Source: https://oceanservice. noaa.gov/education/kits/currents/02tida/1.html I Principles of Geology • Tidal Current ► Slack water - Periods of little or no current and separate flood and ebb. ► Tidal flats - The areas affected by these alternating tidal currents Source: https://marlimillerph oto. com/tidal/lats.html HDA. Reyes I Principles of Geology Lutgens, F., Tarbuck, E. and Tasa, D. (2012). Essentials of Geology Eleventh Edition. Upper Saddle River, New Jersey: Pearson Prentice Hall. https://www. m aIi bu ma kos.com/cu rrents-a nd-d rafts/ HDA. Reyes I Principles of Geology