Skip to content
Quick Guides

Geology - The Shorelines

Preview 4 of 12 pages

See the first 4 pages exactly as they appear in the document.

  1. Page 1
    Read page 1 as text

    Study Guide Geology – The Shorelines 1. Beaches Beaches are one of the most familiar and interesting coastal landforms. They are shaped every day by waves, currents, and sediment movement. What Is a Beach? A beach is the area of sand or gravel (and sometimes silt) that covers the shoreline. It stretches from the low - water edge up to a clear upper boundary, such as a bluff, cliff, or area with vegetation. Key Parts of a Beach • Beach face This is the sloping surface of the beach that faces the ocean. It is usually the steepest part because waves hit it directly and cause the most erosion. • Marine terrace Just offshore from the beach face is a gently sloping platform called the marine terrace. It may only be visible during low tide. This surface can be made of sediments left behind by retreating waves, or it may be solid rock that has been worn down by wave action. • Berm The landward edge of the beach is marked by the berm . This is a raised ridge of sediment deposited by high - energy waves during strong storms. Berms are often made of coarse material and may contain many shell fragments.

  2. Page 2
    Read page 2 as text

    Study Guide 1.1 How Sand Moves Along the Beach 1.1.1 Longshore Dri Ō and Beach Dri Ō Waves usually strike the shoreline at an angle. This angled movement causes sand to travel along the coast in a process called longshore drift . As waves wash up the beach face, they carry sand at the same angle as the incoming wave. When the water flows back toward the sea, it moves straight downhill. This creates a zig - zag pattern of sand movement called beach drift . Over time, this repeated motion can move sand and pebbles hundreds of meters along the beach each day. 1.1.2 Longshore Currents and Sediment Transport Most beach sediment is carried by the longshore current in the surf zone. Breaking waves create friction with the sea floor, loosening sediment and keeping it suspended in the water. The current then transports this material over long distances. Eventually, the sediment is deposited and forms different coastal features, including: • Spits – narrow, finger - like ridges of sand extending from the coast • Baymouth bars – sand deposits that can block a bay from the open ocean • Tombolos – bars of sediment that connect an island to the mainland, forming a small peninsula 1.2 What Beaches Are Made Of Most beaches are made mainly of quartz sand . This sand usually comes from rivers, is carried to the ocean, and then reshaped by waves and currents. Because heavier minerals settle more easily, beaches may also contain dark streaks of dense metallic minerals such as magnetite and ilmenite . In some areas, beach material may include: • Limestone grains • Basalt fragments

  3. Page 3
    Read page 3 as text

    Study Guide The exact composition depends on nearby rock types and sediment sources. 1.3 Seasonal Changes in Beaches Beaches change throughout the year due to seasonal wave patterns. • Summer Gentle waves bring sand from deeper water back toward the shore. This builds wider, smoother beaches. • Winter Strong storm waves erode the beach and carry sand offshore. The sediment is deposited underwater as a sandbar . When summer returns, waves slowly erode the sandbar and move the sediment back onto the beach, rebuilding it. This cycle repeats year after year. 1.4 Human Impact and Beach Engineering Engineers often try to protect beaches and harbors, but these efforts can disrupt natural sand movement. Common Engineering Structures • Breakwaters Built parallel to the shore to create calm water for boats. However, they can cause excessive sediment buildup and may even block off harbors. • Jetties Walls built on both sides of a harbor entrance to reduce sediment buildup and protect against waves. Usually, one jetty traps sand, while the beach on the opposite side is “starved” of sediment and begins to erode. • Groins Short walls built perpendicular to the shore to trap sand and widen eroding beaches. While they help one area, they often reduce sand supply farther down the coast.

  4. Page 4
    Read page 4 as text

    Study Guide 1.5 A Delicate Balance Beaches naturally exist in a balance between sand supply, wind, and wave energy. When humans try to control this system, the results are often unexpected. Changes in one place usually create problems somewhere else, making beach management a challenging ta sk. 2. Shoreline Features The coast is the strip of land located next to the ocean. It includes the beach and the nearby inland area. Coastlines can look very different from one another. Some are steep, rocky, and rugged, while others slope gently and are covered with sand. 2.1 Paleocoasts: Old Coastlines Some coastlines are called paleocoasts . These are ancient coasts that were once underwater. Later, rising sea levels covered them, and tectonic forces eventually lifted them above today’s sea level. As a result, features that once formed on the ocean floor are now exposed on land. 2.2 How Waves Shape Rocky Coasts Waves constantly crash against the shoreline, and over time, they can change even the hardest rock. • Limestone slowly dissolves in seawater. • Soft rocks wear away easily. • Even hard rocks like granite can crack and break due to repeated wave impact. Rocky coastlines are often irregular, with many small bays and inlets. The rocky points that stick out into the ocean are called headlands , and the curved indentations between them are called coves . 2.3 Coastal Straightening Over time, wave action tends to smooth and straighten an irregular coastline. • Headlands receive the strongest wave energy, so they erode faster. • Bays are more sheltered, so erosion happens more slowly there.

8 more pages in the full document

Unlock it once and it stays in your library, ready to chat with or turn into flashcards.

Unlock the full document

More Geology study materials

See all

Study this document with CramX

Once it is in your library, every tool can work from it.