صفحه 1:
دا همه
صفحه 2:
Or Re ord
Cee فص
۱ oe Ol CN eR SN Bara
00 ASL
my
3 =
nn Foreshore Backshore
Offshore Shoreface ———_ Beach —__>
صفحه 3:
ل داق
Oe a eR a A a
Ne Ns ea Od So
CON aA ard NS A en oe SR he Ad
zoues ts Painwedher wove bose — the depik ot whick wouter is oPPevted
۱ مر مه
Offshore Shoreface
صفحه 4:
مره
ال لك
صفحه 5:
اج مس سم ene ی
اي ا اك
سس مه مها
هه رت تا
۳ مطلمب عامي me od
تم مات مات مت تا
هط ام
يي ل
Shoreface
صفحه 6:
(Qe (ome eval
اي ل فاك
ل ا
كلابب ممشعضةا صا صبك مك لجنيواد
لي ان
10
ل 0
هت
ال
FA aN ل
مس
صفحه 7:
(Ghose ce (aca ae Deel)
Od eee te
ی ae
Se eee
جا ممه ينضحب ج١1 .جاص تخاصصنا
000 ee el ee
ود
0 سي ا
مسا اعد et
ee تشر
See oe aie
ete oy ac ete
BN
___ Shoreface
صفحه 8:
Ga: ren wey)
Ce اي ac id
(god evectudly sips) ic its
Nee Rd
reas NCE at aa cash PA عصاصب جص
NR ccc a
(۳ مرت as
شا سوت ماس ملسم Foreshore
۱۱ 4 Shoreface
مرو
صفحه 9:
مسرت(
eee ek scene nee
See ed
Seater
Dunes!
Be
++ High tie love:
0 Foreshore
تك وه ات و امه بط یا
000 eae
صفحه 10:
Cee ا Sa
Ea ee ea ac ead
dowivated by deposition (us is the cose Por saad beaches), vihers
۰و برط لصادواصصك جص
صفحه 11:
تسم سم مات
تسس
ل لك ل ل نكا
Ce een ea aa are
dic
اسف همهم هس
ماص المي 1
ل سوت و(
naa al سس هس مت
تست ما مه رتم
Rae را
صفحه 12:
0
Okeu يعدا ه جعصامج عصط ه body
0 its Plow
۳ i و R acd
Neer ea Coase oe a
مت
cand ل ا الك
نك
صفحه 13:
0
RE roa ۱
سر و اه ومد
aNd مت
وا یس متسه
وس رورس متا
asec ۱
.ماصك سرت
صفحه 14:
OTR rE sa ae ca RR ae
Oost waves wove
Ce ea
ور
9 ]
عصامرن خأن عاصصون:
ل
۱
صفحه 15:
با جاسی)
ها كاعصيك خام مس هی(
.ام
۱0
تست ها
صفحه 16:
صفحه 17:
Qip Curreuts
Ce eee ae der aa eee
Fe ee Rte eet ned taeda ea ae
COR ete eae On eee Capea cee) Poa ceed
eh ve eed
Return Flow Return Flow
۲ ۲ +— Rip Currents ع + + +
ل ل
_ ل
صفحه 18:
ees
مسد نا سه با 0
(eee Saree ene) اس همست
۱۱۱۶ a ip correct is diPPeredt Pow uederiow
صفحه 19:
و(
مه و وج وه موی رت مرت Oe eae
ا نا موس ما هت مایت تسه
| ویو
]۱ eet lee none ater Leet Cee ae
.صمب ا عادص طون
0
10۳
Cea coed ee eee ee
en ee ۳
dana (خصصح ويه هذ نج للج عدقاص لعجن جاسم داعو جز
صفحه 20:
kG ad ان د
تساه ۲ هو موم له
ce acc ا اه عون
دمص هی تا
VAS CAS A CARA oe ۱
NC AA ao ات(
PURER Cea at a Road
اه وتو له موه با لصوم
تست رم سم تست
FeO A a Cas SE NCAA SS Ca oe
a aoe
صفحه 21:
لك
Sora polyps
00
۱
0
0111 cee eel cece ee ee eres een cc
1 eee pace ae ot as)
صفحه 22:
OS a a a a
ee TL CAE oe SR eR a a oe oe Moe و و۱۳
]) 60 vorboudte is eusier tv previpitate iat warn woter tro io volt
ار
] CASR mE Cas SCA CASS CANS CaSO PANS Cocoa a جموه خان
that live to the fissures oP reeP builders (the okjae rewove carbo
dioxide Prov the tissues, decreusiay the avidity oP the wuter).
صفحه 23:
2 ا ۱60
(Ne RIN ed A aaa he A ee cue cae
CRN Ras Naa acd (ACE Su a
perches eee
©. محش( levels ore law.
2 aed
صفحه 24:
Nae
CeO a a ea ات مت هه
۱ ا و
ا CARS aS NSD SR eS CA PA cece a
PR aN a Cn a oD)
BEEF REEF REEF FORE
ها 6 FRONT EF
0
Encrusting to Domai
Massiv
to globular to domal
Evaporites
Carbonate Solid
gravel reef
Carbonate mud and framework
sand
gravel and sand
aR a aa Ree ا
Sed
صفحه 25:
لك
سس
BIKINI ATOLL
ee SS aR Ras as صاخ
Dec a A a ae cs Ca)
كت
صفحه 26:
ORC RC acc
توص مق ات ما و وف سس متا خر
Tee tN al A ce SS CC Re
crust hus cooled, bevowwiny deuser), he reeP couicues to build
ال PA ROCA Ra CN ail tao
ی ۱
صفحه 27:
تا
BIKINI ATOLL
Ck (Cac a RCN ad EE aC ae cic od
OCR cr aR ear a on Coe oe ol eel OD RN ار
۱ ole
۱۳ Coe
صفحه 28:
ها 31000
لك
a aa كا
صفحه 29:
EOO OF LECTORE
صفحه 30:
۱۸۱ BUI ce NS VARS ras cat ea
ایس همست
coe con ecm Moe Caan ceo ۱
CA ol an aM aca Reid Bec oe Pence وص كحو
Tea oN
Coasts and Reefs:
Shallow marine processes
Coastal System
A beach is part of a coastal system, which includes several zones
defined by their proximity to shore and the dominant processes that
occur within them.
Offshore to Shoreface
Offshore and shoreface portions of the coastal profile are permanently
submerged in water, below the low tide mark.
An important feature that separates the offshore from shoreface
zones is fairweather wave base – the depth at which water is affected
by wave movement under normal weather conditions.
Offshore zone
The offshore zone lies below
fairweather wave base and is
therefore unaffected by normal
waves.
The offshore zone normally only
receives fine sediment that settles
from suspension (but can receive
coarser grained sediment during
storms, when wave base is
lowered).
Shoreface zone (lower part)
The shoreface zone lies above
fairweather wave base and is
constantly affected by normal waves.
The gentle gradient of the lower
shoreface results from the smoothing
out of sediment associated with the back
and forth movement of the waves.
Shoreface zone (upper part)
Near the top of the shoreface
zone, the base of a wave is
slowed down due to friction with
the seabed
The wave is oversteepened, and
breaks, losing much of its
energy.
Due to the loss of energy, some
sediment can be deposited in sand
bars.
Foreshore (The lower part of a beach)
Once a wave breaks, its water
moves as a sheet upslope as swash,
and falls back toward the sea as
backwash. The narrow area in
which this occurs is called the swash
zone.
The location of swash zone shifts
due to the rising and falling of the
water level, associated with tides.
The area affected by the swash
zone on a daily basis is called the
foreshore (between low and high tide
marks)
Foreshore (the lower part of a beach)
As the flow of swash slows
(and eventually stops) in its
upper reaches, some of the
sediment carried by the water
can be deposited.
But much of the sediment is
returned back down to the
upper shoreface due to
backwash.
Backshore
Beyond the Foreshore of some
beaches is a backshore zone,
characterized by dunes. Dunes
are constructed by windblown
sediment transported from the
foreshore and elsewhere.
Sediment can also be transported
to the backshore area during
storms, when big waves can
reach far inland (note that a storm
beach face can be seen well away
from the normal beach face).
So where does beach sediment come from ?
Not all shorelines are alike. Whereas some shorelines are
dominated by deposition (as is the case for sandy beaches), others
are dominated by erosion.
Erosional shoreline area
(material removed)
Depositional shoreline area
(material deposited)
Sediment from coastal erosion
Shorelines characterized by
exposed bedrock and strong
wave activity are important
suppliers of beach sediment.
Basalt
Minerals of beach sediment
derived mostly from eroded
rocks along the coast match
those of the source rocks.
Black sand
Black sand beach, Big Island, Hawaii
Sediment from rivers
…But most sediment supplied to
beaches along continental coastlines
is delivered to the coast by rivers.
When a river enters a large body
of water (e.g. ocean), its flow
rapidly decreases, resulting in the
deposition of sediment at the river
mouth.
The resulting sediment deposit is a
delta.
Mississippi delta
(a river-dominated delta)
Sediment transport away from river mouth
If wave action is
strong, sediment
deposited at a river
mouth can be
transported along the
coastline instead of
forming a welldefined delta.
Sediment
reworked by
waves and
transported
along coastline
How is sediment transported along a coastline ?
Most waves move
toward the shore at a
slight angle.
Consequently, the
uprush of water
(swash) from each
breaking wave is
oblique.
Beach drift
The direction of swash is
oblique.
However, the backwash
runs back to the water at a
right angle.
Sediment particles are
therefore transported in a
zig-zag pattern along the
beach.
This “beach drift” can
carry sand and pebbles
hundred to thousands of
metres per day.
Longshore drift
In a similar manner, water
in the shoreface zone flows
toward the shore at an angle,
and flows back at a right
angle to the shore.
The net result is a current
that flows parallel to the
shore. This is called a
longshore current.
The movement of
shoreface sediment by a
longshore current is called
longshore drift.
Lon
ft
i
r
d
e
g s h or
Rip Currents
Breaking waves approaching the beach carry water toward the beach. The
water can't just pile up there: it has to escape back out to sea somehow.
Various “paths of least resistence” (e.g low areas along sandbars) provide areas
for water to flow back to the sea.
If caught in a rip current, swim parallel to shore !
How to spot a rip channel
Rip channels
(as seen from the air)
Rip channel
(as seen from beach)
Note: a rip current is different from undertow
Head of
Rip channel
Undertow
Undertow results when water cannot escape as a rip current.
Remember that water that is pushed toward the beach must return to the sea
somehow !
If the water can’t escape as a rip current, it returns to the sea by flowing
underneath the waves.
Swimmers are less likely to drown from undertow than in a
rip current (most so-called “undertow drownings” result from swimmers losing
their balance in backwash and getting pulled out in a rip current).
A Short Note on Reefs
Another prominent feature of shallow
marine settings is the reef.
Reefs are natural structures of rock
formed by marine animals.
Today’s reefs are largely made by corals,
but in the geological past, have been
constructed by sponges and bizarre clams.
Reef-building organisms build skeletons of
calcium carbonate in the form of aragonite
or calcite.
Great Barrier Reef,
Australia
The Beauty of Reefs
Coral polyps
(individual coral animals)
Coral reefs are often called the “rainforests of the sea” due to the
great diversity of creatures that form them. Note that the brilliant colours
apparent in corals are from the microscopic algae in the coral tissues (different
colours absorb different wavelengths of light)
Conditions necessary for reef development
Large reefs are limited to the warm seawater areas of the tropics.
Calcium carbonate is easier to precipitate in warm water than in cold
water.
Secretion of calcium carbonate is aided by microscopic cells of algae
that live in the tissues of reef builders (the algae remove carbon
dioxide from the tissues, decreasing the acidity of the water).
Conditions necessary for reef development
Reefs also tend to preferentially form in areas where:
1. Little clastic sediment occurs (such sediment particles
smother reef builders).
2. Nutrient levels are low.
3. Water is shallow
Reef zones
Reef builders are zoned in a reef according to their form (encrusting
forms tend to dominate the reef crest where wave action is strongest,
while more delicate branching forms are confined to deeper water
zones where water action is more gentle)
A lagoon can develop behind a reef, where it is protected from
strong waves
A special kind of reef: atoll
An atoll is a special kind of reef that is ring-shaped and has a central
lagoon. It is likely that Gilligan’s Island was set in an partially formed
atoll.
How an Atoll Forms
An atoll is formed first as a reef that fringes a volcanic island.
As the island sinks (after volcanic activity has ceased and the
crust has cooled, becoming denser), the reef continues to build
upward, eventually ending up as a ring-shaped structure.
Gilligan’s Island ?
Bikini Atoll
Bikini atoll (central Pacific) is a famous nuclear testing site
(the US tested atomic bombs here in the 1940s and 1950s)
So it makes sense that the “new swimsuit for the atomic age”
was named…guess what.
…And we end up back at the beach
The bikini
Enjoy your break !
END OF LECTURE
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