The protected embayments, where wave action is subdued between headlands, are often transformed into sandy pocket beaches. Waves are refracted around the headlands, increasing erosion at seaward positions on the islands in the park. Headlands and pocket beaches of Channel Islands National Park in California are distinctively shown in aerial photographs. Headlands, Pocket Beaches, and Wave Refraction Also see U-Shaped Valleys, Fjords, and Hanging Valleys as part of Glaciers & Glacial Landforms. Kenai Fjords National Park in Alaska provides excellent examples of rocky coasts along fjords. The inundated valleys created by glacier movement are called fjords. Fjordsīetween 1.8 million to 10,000 years ago, Pleistocene glaciers carved steep valleys that were eventually drowned by rising sea levels. Fjords are made when glacial valleys are filled with water when sea level rises. Bluffs, cliffs, and terraces form as rock is eroded. Waves cut arches and sea stacks that jut into the water. Rocky coastlines have many spectacular features. Carbonate coasts, dominated by skeletal and shelly materials, may form eolianite dunes-calcium carbonate beach dune deposits that are lithified and may be eroded to form steep cliffs and bluffs. In addition, glacial activity may produce steep, rocky coasts through the production of fjords and talus slopes. Resistant bedrock combined with high-energy wind and wave activity will create a steep profile, whereas easily erodible rocks in low-energy environments will create a more gradual profile, for example, the high cliffs of Kalaupapa National Historical Park (Hawaii) versus the gently sloping rocky coastline of Dry Tortugas National Park (Florida). Bedrock composition, climate, and wave patterns dictate the profile of rocky coasts. Rocky coasts may be composed of any rock type (i.e., sedimentary, igneous, or metamorphic) and are usually the site of complex tectonic landforms such as faults, folds, and igneous intrusions and extrusions. Erosion characterizes these high-energy environments, which are typically located on active margins with narrow continental shelves (on account of subduction). The pounding surf and breaking waves found on rocky coasts have inspired ocean lovers for generations. A wave crashes into the rocks at Ship Harbor in Acadia National Park, Maine.
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