![]() David Murphy, used with permission in Steven Earle, “Physical Geology”). The arch has collapsed and a small stack remains (Photo: Dr. During the winter of 2012-2013, the arch collapsed, leaving a small stack at the end of the point.įigure 13.3.3 Top: An arch in tilted sedimentary rock at the mouth of the Barachois River, Newfoundland, July 2012. This feature started out as a sea cave, and then, after being eroded from both sides, became an arch. An arch in the Barachois River area of western Newfoundland, Canada, is shown in Figure 13.3.3. If a hole develops in the ceiling of a cave, a blowhole can be created, shooting water into the air when waves crash in the cave. Wave action and strong longshore currents can carve a cave into a headland, and if the erosion extends all the way through, it becomes an arch. The wave-eroded surface is submerged at high tide (Steven Earle, “Physical Geology”).Īrches and sea caves form as a result of the erosion of relatively non-resistant rock. A wave-cut platform extends across the intertidal zone.įigure 13.3.2 A wave-cut platform in bedded sedimentary rock on Gabriola Island, B.C. The result is that the substrate in the surf zone is typically eroded to a flat surface known as a wave-cut platform (or wave-cut terrace) (Figure 13.3.2). Wave erosion is greatest in the surf zone, where the wave base is impinging strongly on the seafloor and where the waves are breaking. The blue arrows represent wave energy most of that energy is focused on the headlands, causing greatest erosion in this area (PW). The result of this is coastal straightening, where an irregular coast will eventually become straightened, although that process may take millions of years.įigure 13.3.1 The approach of waves (blue lines) towards a coastal headland. On irregular coasts, the headlands receive much more wave energy than the intervening bays, and thus they are more strongly eroded. That energy is evenly spaced out in the deep water, but because of refraction, the energy of the waves is being focused on the headlands. In Figure 13.3.1, wave energy is represented by the blue arrows. ![]() When waves approach an irregular shore, they are slowed down to varying degrees, depending on differences in the water depth, and as they slow, they are bent or refracted ( section 10.3). Large waves crashing onto a shore bring a tremendous amount of energy that has a significant eroding effect, and several unique erosion features commonly form on rocky shores with strong waves. "The coastal strip, 55 km long, is characterized by steep rocky cliffs broken by rolling slopes, as well as by stacks. ![]() "The rocky headlands, beaches, tide pools nurturing a living rainbow of colors and textures, off shore sea stacks topped by nesting seabirds and wind-sheared trees-all are a remnant of a wilder America." The coastline is generally rocky with a several offshore islets and stacks. The livid, sheer, and jagged cliffs of the coast contain many grottos and areįlanked by numerous stacks, islets, and coves (Coastal WHS) There are numerous sea stacks along the shore. The small rock in the foreground is probably a sea stack in. ![]() ".and there are numerous offshore islets, stacks and rocks - most within 100 m of the main island, and none at a distance greater than 1 km." (UNESCO web site) Another interesting land form on the rugged coast just off Bay Bulls in Newfoundland, Canada. ![]() Cocos island is surrounded by several islets, some of them like Manuelita island, isla Pájara and "the moais" rise quite abruptly from the sea. ![]()
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