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1 Your web browser (Safari 7) is out of date. For more security, comfort and the best experience on this site: Update your browser Ignore cliff BLU FF For the complete encyclopedic entry with media resources, visit: A bluff is a type of broad, rounded cliff. Most bluffs border a river, beach, or other coastal area. Bluffs may form along a river where it meanders, or curves from side to side. River currents on the outside of the curve erode, or wear away, the lower part of a river bank. No longer supported, the upper part of the bank breaks off, leaving the high wall of a bluff. The 150-meter (500-foot) Great River Bluffs in the U.S. state of Minnesota, for example, were carved by the meanderings of the mighty Mississippi River. Erosion also produces bluffs along the wider flood plain of a river. Over thousands of years, a meandering river gradually shifts from side to side across its flood plain. Where the meanders, or loops, of the river reach valley walls, the water may carve bluffs. In fact, a bluff line defines the outer limits of a river s flood plain, and is often another name for valley wall. A flood plain s bluff lines may be steep and narrow, or they may be wide and gentle. Coastal bluffs are formed through a combination of erosion from wind, sea spray, and crashing waves. These bluffs are often more rugged than their inland counterparts, and are more vulnerable to major erosion. Coastal bluffs, especially those in the Puget Sound region of the U.S. state of Washington, are sometimes called feeder bluffs. The constant erosion of feeder bluffs supplies (feeds) sediment to the beaches and seashore downstream below. 1 of 6

2 Another sort of coastal bluff is the beach ridge. Beach ridges are formed entirely by waves lapping onshore, pushing sand and sediment up and away from the body of water. Beach ridges run parallel to the shoreline and are often associated with sand dunes. The Indiana Dunes, for example, are extensions of beach ridges formed by the waters of Lake Michigan. At this national lakeshore, tiny bluffs give way to larger dunes, and the ecosystem eventually creates the ideal conditions for an oak forest through the process of plant succession. Like many types of cliffs, bluffs provide important information about how Earth developed. Scotts Bluff, for instance, rises more than 1,400 meters (4,600 feet) above the North Platte River in the U.S. state of Nebraska. The exposed rock of this national monument allows geologists to peer more than 30 million years into North America s past. Rock formations at Scotts Bluff preserve the history of ancient volcanic activity nearby, as well as the fossilized presence of prehistoric North American rhinos, tapirs, and even camels. Life on the Bluff The summits of many bluffs are bare, rocky outcroppings. However, the harsh environment of bluffs are often vital ecosystems. Tiny organisms called lichen often colonize rocky bluffs, providing vital nutrients for many insects and birds. Hardy grasses and shrubs can also take root on rocky bluffs. The shallow roots of these plants slow erosion of the bluff, even helping to secure valuable topsoil in some places. Bluffs provide an ideal nesting spot for fishing birds such as cormorants and kingfishers. Cormorants build their nests on the bare ground of bluffs, bringing sticks and seaweed for construction. Cormorant colonies can grow so large that they take over the entire bluff. Kingfishers don t nest on top the bluff, but dig a burrow directly in it. They prefer burrows on bluffs with little vegetation, as root systems get in the way of digging. 2 of 6

3 Bluffs are even home to endangered species. The El Segundo blue butterfly, for example, is found only in a small bluff ecosystem near the giant Los Angeles International Airport in Southern California. Vocabulary Term Part of Speech 3 of 6 Definition beach narrow strip of land that lies along a body of water. beach ridge bluff steep cliff. bluff line small bluff running parallel to a shoreline, formed by waves pushing sand and sediment away from that shoreline. furthest extent of a flood plain, where the valley floor begins to rise. Also called a valley wall. border verb to exist on the edge of a boundary. broad adjectivewide or expansive. burrow small hole or tunnel used for shelter. cliff steep wall of rock, earth, or ice. coast edge of land along the sea or other large body of water. current dune ecosystem endangered species environment steady, predictable flow of fluid within a larger body of that fluid. a mound or ridge of loose sand that has been deposited by wind. community and interactions of living and nonliving things in an area. organism threatened with extinction. conditions that surround and influence an organism or community. erode verb to wear away. erosion act in which earth is worn away, often by water, wind, or ice. extension additional part of a larger project or organization.

4 feeder bluff flood plain coastal cliff that provides sand and sediment to downcurrent beaches as it erodes. flat area alongside a stream or river that is subject to flooding. fossilize verb to become a solid mineral. geologist person who studies the physical formations of the Earth. hardy lichen adjectivestrong or able to withstand severe weather. organism composed of a fungus or fungi and an alga or cyanobacterium. meander verb to wander aimlessly. national monument nest federal land set aside to protect objects of scientific and historical interest. protected area built by birds to hatch their eggs and raise their young. nutrient substance an organism needs for energy, growth, and life. outcropping parallel layer of rock visible above the surface of the Earth. adjectiveequal distance apart, and never meeting. peer verb to glance or gaze. plant succession prehistoric process of one plant community dying off and creating conditions for a new type of plant community to replace or succeed it. period of time that occurred before the invention of adjective written records. river large stream of flowing fresh water. river bank raised edges of land on the side of a river. rock natural substance composed of solid mineral matter. root Term root system rugged Part of Speech part of a plant that secures it in the soil, obtains water and nutrients, and often stores food made by leaves. all of a plant's roots. Definition adjectivehaving an irregular or jagged surface. 4 of 6

5 Term Part of Speech Definition seashore beach or coast. sea spray airborne particles formed from the ocean, largely composed of water, salts, and organic materials. sediment solid material transported and deposited by water, ice, and wind. shrub type of plant, smaller than a tree but having woody branches. summit highest point of a mountain. topsoil the most valuable, upper layer of soil, where most nutrients are found. valley depression in the Earth between hills. vegetation all the plant life of a specific place. vital adjectivenecessary or very important. volcanic adjectivehaving to do with volcanoes. vulnerable adjectivecapable of being hurt. wind movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun. Articles & Profiles ehow: What Are the Landforms Called Bluffs? World Landforms: Bluff Landforms Interactives University of Wisconsin-Madison, Department of Geography: Bluff Erosion Visualization Worksheets & Handouts National Park Service: Scotts Bluff Geographic Landforms 5 of 6

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Your web browser (Safari 7) is out of date. For more security, comfort and the best experience on this site: Update your browser Ignore CO NTINENTAL SHEL F For the complete encyclopedic entry with media