Rocky CoastsIsabella GarramoneOceanography Fall 2009
General Overview• 75% of the world’s coasts are rocky.• “As with most landforms rocky
shores reflect the structure and
strength of the exposed lithologies, the physical and chemical processes acting on them, and the time they're
allowed to do so. “
• Waves approach a shoreline from all sides in varying angles.
• The surf erodes softer rock faster than the surrounding rock.
• Rocky coasts have a narrow continental shelf that pitches sharply from land to sea.
Shaping of Rocky Coasts• Physical Weathering: the erosion of land by waves, wind, or
the movement of glaciers.
• Chemical Weathering: hydrolysis, oxidation, and salt
weathering.
• Bioerosion: the erosion of land by algae or other organisms
that either dissolve layers of rock or tunnel into it.Mainly on coasts made of carbonate.
Limestone bored by clams
and sponges (bioerosion).
Geologic Features of Rocky Coasts
• Fjords:
formed when glacial valleys fill with water when the
sea lever rises.
• Pocket Beaches:
protected embayments where wave action
is subdued and sediment is not carried away.
• Sea Caves:
carved out from bedrock by prolonged wave
action.
• Sea Cliffs:
a very steep slope separates flat land from the
water.
• Sea Arches and Sea Stacks: isolated remnants of the
mainland that will eventually be completely eroded away.
•After caving in, a sea arch becomes
a sea stack which will eventually
become a sea stump.
Sea Cliff
Where are Rocky Coasts Found?
• Found where there is a history of erosion exceeding rates of
sedimentation, or sediment is either low or not retained.
• Active Tectonic Environments– volcanic islands: rapid uplift inhibits the development of sediment
equilibrium (reef development is common)
– Example: parts of the coast of California
• Where Mountains and the Sea collide
• Where glaciers played a large role in carving out the
landscape; rapid glacial escape leaves little material behind to
make beaches.– Examples: Maine & Alaska
Shipwreck Coast: Victoria, Australia
• Shipwreck Coast is made primarily of
limestone.
• There are numerous sea stacks in the water &
underwater rock formations that have
sunken more than 200 ships.
Species that Live on Rocky Coasts
• Many species live in tide pools on top
of the rocks, such as snails and
macroinvertebrates.• Algae, such as bladderwort, clings and
grows off of the rocks.• Smaller fish & organisms (such as
juvenile lobsters) find refuge from
predators in the underwater crevices
the rocks provide.• The animals living in the intertidal
zones must be able to withstand being
underwater and above water for
prolonged periods.• Barnacles
attach themselves to the
rocks as a base and use it as leverage
to sweep the surrounding area for
plankton.
Rocky Coasts + Global Climate Change• As glaciers melt and sea level
rises, rocky coastlines will
become even more eroded than
before.• Many sea arches and sea stacks
will tumble or some sea caves
may enlarge or cave in.• Increasingly turbulent storms as a
results of warmer waters will
erode the exposed rocks more
rapidly.• The waves produced by these
larger storms will also erode the
rocks at sea level more rapidly.
Works Cited
• Hanson, Lindsay S., . "Rocky Coasts." Geomorphology. Salem State College
Department of Geological Sciences, Web. 23 Sep 2009.
<http://w3.salemstate.edu/~lhanson/gls214/gls214_rocky.html>
• "Oceans." Erosional and Depositional Features of Waves. Vancouver School Board,
Web. 24 Sep 2009.
<http://stloe.most.go.th/html/lo_index/LOcanada6/606/6_en.htm>.
• "Rocky Coasts." Geologic Features of Rocky Coasts. National Park Service, Web. 24
Sep 2009.
<http://www.teachersdomain.org/ext/ess05_int_coastrock/05_R_GeoFeatures.ht
m>.
• Wilson, Mark A., . "Bioerosion." The College of Wooster Department of Geology,
Web. 23 Sep 2009.
<http://www3.wooster.edu/geology/Bioerosion/Bioerosion.html >.