Rocky Coasts Isabella Garramone Oceanography Fall 2009 General - - PowerPoint PPT Presentation

Rocky Coasts

Isabella Garramone Oceanography 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.

Pocket

• 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
• f 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 >.