• If you've ever been to the beach, you've been on a coast. The coast is the land along a sea. The boundary of a coast, where land meets water, is called the coastline.

    Waves, tides, and currents help create coastlines. When waves crash onto shore, they wear away at, or erode, the land. But they also leave behind little parts of the sea, such as shells, sand dollars, seaweeds, and hermit crabs. Sometimes these objects end up as more permanent parts of the coastline.

    Coastal changes can take hundreds of years. The way coasts are formed depends a lot on what kind of material is in the land and water. The harder the material in the land, the harder it is to erode. Coastlines of granite, a hard rock, stay pretty stable for centuries. Sugarloaf Mountain, on the coast of Rio de Janeiro, Brazil, is made mostly of granite and quartz. It has been a landmark for centuries.

    The famous White Cliffs of Dover, in England, are made of calcium carbonate. This is a soft material and erodes easily. However, it exists in such great quantities that years of erosion have not made a visible impact on the coastline. The White Cliffs are a landmark of the English coast of the English Channel. (The other coast is French.)

    The sandy coastlines of islands, on the other hand, change almost daily. The island of Mont Saint Michel is only an island when the tide is in. It is part of the coast of France during low tide. Islands are also the site of Earth's newest coastlines, like a Tongan island created in March 2009 by the eruption of the volcano Hunga Tonga-Hunga Haapai. The "Big Island" of Hawaii, created by five volcanoes, sometimes expands its coastline when one of its active volcanoes, Mauna Loa or Kilauea, erupts. If lava flows reach the ocean, the lava cools and forms new coastline along the Pacific Ocean.

    Tides, the rise and fall of the ocean, affect where sediment and other objects are deposited on the coast. The water slowly rises up over the shore and then slowly falls back again, leaving material behind. In places with a large tidal range (the area between high tide and low tide,) waves deposit material such as shells and hermit crabs farther inland. Areas with a low tidal range have smaller waves that leave material closer to shore.

    Waves that are really big carry a lot of energy. The larger the wave, the more energy it has, and the more sediment, or particles of rock, it will move. Coastlines with big beaches have more room for waves to spread their energy and deposits. Coastlines with small, narrow beaches have less room for waves to spread out. All the waves' energy is focused in a small place. This gives the small beaches a tattered, weathered look. Sandy beaches are washed away, and rocky coastlines are sometimes cracked by strong waves.

    Because coasts are dynamic, or constantly changing, they are important ecosystems. They provide unique homes for marine plants, animals, and insects. Coasts can be icy, like the Shackleton Coast of Antarctica, or desert, like the Skeleton Coast of Namibia.

    Coasts help us understand natural events, such as weather and changing sea levels. During storms, coasts are the first places to be flooded. Some coasts have coastal plains. Coastal plains are pieces of flat, low-lying land that can become visible when sea levels start decreasing.

    Coasts, as beautiful as they tend to be, have it rough sometimes. They are affected by pollution, oil spills, and garbage from both land and sea. Pollution negatively affects the way a coast looks and is damaging to the marine life that lives there.

    People visit the coast on vacation to participate in activities like fishing, boating, and swimming.

    In the United States, coasts can be a reference to culture as much as physical geography. For example, West Coast people in California identify with a different type of culture, or way of life, than East Coast residents in New York City or Washington, D.C. The southern Gulf Coast of New Orleans, Louisiana, has yet a different cultural association.

    This cultural connection to the coast shows up in many different ways, including food and leisure activities. Residents of the Gulf Coast, for instance, are more familiar with food made from shrimp, a seafood native to the warm waters of the Gulf of Mexico. Maine, on the northern East Coast, is famous for its lobster.

    Rocky coasts can be dangerous.

    Banks and Shores
    Technically, the land next to rivers and lakes is coastal. But river coasts are called banks and lake coasts are called shores.

    The Most Coast
    . . . Canada has 202,080 kilometers (125,567 miles) of coastline.

    Short But Sweet
    . . . Monaco has 4 kilometers (2.5 miles) of coastline.

  • Term Part of Speech Definition Encyclopedic Entry
    beach Noun

    narrow strip of land that lies along a body of water.

    Encyclopedic Entry: beach
    calcium carbonate Noun

    chemical compound (CaCO3) found in most shells and many rocks.

    coast Noun

    edge of land along the sea or other large body of water.

    Encyclopedic Entry: coast
    coastal plain Noun

    low, flat land lying next to the ocean.

    Encyclopedic Entry: coastal plain
    coastline Noun

    outer boundary of a shore.

    culture Noun

    learned behavior of people, including their languages, belief systems, social structures, institutions, and material goods.

    current Noun

    steady, predictable flow of fluid within a larger body of that fluid.

    Encyclopedic Entry: current
    decrease Verb

    to lower.

    dynamic Adjective

    always changing or in motion.

    East Coast Noun

    Atlantic coast of the United States.

    ecosystem Noun

    community and interactions of living and nonliving things in an area.

    Encyclopedic Entry: ecosystem
    energy Noun

    capacity to do work.

    English Channel Noun

    strip of the Atlantic Ocean between southeast England and northwest France.

    erode Verb

    to wear away.

    flood Verb

    to overflow or cover in water or another liquid.

    garbage Noun

    trash or waste material.

    granite Noun

    type of hard, igneous rock.

    Gulf Coast Noun

    land in the United States surrounding the Gulf of Mexico.

    hermit crab Noun

    type of marine animal (crustacean) that uses found materials, such as other creatures' shells, as its shell.

    high tide Noun

    water level that has risen as a result of the moon's gravitational pull on the Earth.

    island Noun

    body of land surrounded by water.

    Encyclopedic Entry: island
    low tide Noun

    water level that has dropped as a result of the moon's gravitational pull on the Earth.

    marine Adjective

    having to do with the ocean.

    oil spill Noun

    accidental release of petroleum products into a body of water, either by an oil tanker or an offshore oil rig.

    pollution Noun

    introduction of harmful materials into the environment.

    Encyclopedic Entry: pollution
    quantity Noun


    quartz Noun

    common type of mineral.

    sand dollar Noun

    type of marine animal (sea urchin) that is flat and lives on the ocean floor.

    sea level Noun

    base level for measuring elevations. Sea level is determined by measurements taken over a 19-year cycle.

    Encyclopedic Entry: sea level
    seaweed Noun

    marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.

    sediment Noun

    solid material transported and deposited by water, ice, and wind.

    Encyclopedic Entry: sediment
    shell Noun

    hard outer covering of an animal.

    tidal range Noun

    the difference in height between an area's high tide and low tide.

    tide Noun

    rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.

    Encyclopedic Entry: tide
    wave Noun

    moving swell on the surface of water.

    weather Verb

    to change as a result of exposure to wind, rain, or other atmospheric conditions.

    weather Noun

    state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.

    Encyclopedic Entry: weather
    West Coast Noun

    Pacific coast of the United States, usually excluding Alaska.