Sedimentary Environments: Beach

PROCESS OF FORMATION WHATTA A beach is formed by the action of waves and current and wind along the shore. Winds may bring lighter materials such as sand and also cause bigger particles to erode. Waves may either bring or take away sediments. Waves can carry bigger particles such as pebbles and cause bigger particles to erode and cause them to be round or discoidal in shape. Waves may also bring up sediments from the sea (such as coral and shell fragments). Rivers can carry sediments from higher altitudes like mountains. Over time, grains are broken up by attrition. BEACH?! An important part in the beach's formation is a process called longshore drift, where waves or winds deposit particles while travelling at an angle to the coastline. Over time, these particles are transported farther and farther away from their original spot through a line materig parallel to the shore. High tide mark Visited by over millions every year, and featured in all sorts of media, such as leisure magazines, travel documentaries, and almost every anime series, the beach is trulya popular attraction. But what exactly is a beach? Is it a bird, is it a plane? Can it be eaten? This infographic attempts to provide pieces of information regarding the beach, its formation, its parts and Movement Unlike headlands and cliffs, the beach has the ability to rebuild itself and repair the damage caused by the sea. The components of repair are: beach sand being able to dry because of a receding tide and sunshine and wind; sea wind to blow the sand inland, a sand storage in the dunes. Thus a beach can store sand and grow during years of good sea winds, few rains or storms and much sunshine. As the sand pump pumps sand from the wet beach, it causes the beach to lie steeper. During years with opposite conditions, the beach can erode and lie flatter. 16 Oblique waves Direction of waves components. A beach is a depositional landform', created during the buildup of unconsolidated particles between the areas where the highest and lowest waves hit. These particles are often deposited near the shore, while larger grains (such as pebbles) are transported during storms and other events when there is higher energy present in the waves.' Over time, the grains near the shoreline are broken up by attrition into finer pieces such as sand. This leads us to the beaches we know today, due to the constant action of waves, tides, and currents. ACCRETION YEARS sea winds few rains few storms much sunshine * EROSION YEARS land winds many rains manystorms little sunshine Most people regard the beach as the dry sandy part of the shoreline. However, geologists define it as the sedimentary environment that extends from the sand dunes landward of the high tide line to the point offshore where water depth reaches 10 meters. Seaward from here is the continental shelf.5 While the dry beach accretes, While the dry beach erodes, the wet beach shrinks. The beach lies steeper. the wet beach accretes with old and new sand. The beach lies flatter. SETTING SHELF to 150m depth BEACH Although beaches are commonly associate with seashores, beaches are not limited to those areas. The beach is generally found along shorelines not just of seas and oceans but also of rivers and lakes. Any system where rock matrials move onshore or offshore (or even alongshore) by the forces of waves and currents are considered beaches. Beaches are found in all seven. continents. 10m depth Most beaches are sandy. However, some are sites of gravel disposition and are called shingle beaches. These are common along rocky coastlines or in cool temperate clímates. Colder areas have less intense chemical weathering resulting in larger sedimentary particles, which tend to be very well-rounded and discoidal in shape." AGENTSOF SEDIMENTARY TRANSPORT Water is the main agent involved when it comes to the deposition of sediments on a beach. Sediments may come from rivers flowing towards the coast 14 and from sediments in the ocean itself. Longshore drift569 is also involved in depositing sediments across the coastline. Waves and tidal currents transport sediments through the following ways: GEOMETRY The beaches we are most familiar with are those long and narrow coast as far as the eye can see. These are summer beaches, when gentle waves deposit sand form deep into the ocean to the shore. These are in contrast to winter beaches, which are noticeable for having a much shorter coast due to sand being brought back to the ocean by more violent waves. Thus, a beach may have two different environments, depending on the season. Minerals are dissolved in sea water and carried in solution. The load is not visible. Load can come from cliffs made from chalk or limestone, and calcium carbonate is carried along in solution. SOLUTION Small particles are carried in water, e.g. silts and clays, which can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds generate high energy waves. SUSPENSION In summer, the beach is covered by sand that is moved south by the longshore currents and onshore by low tide waves. In winter, the beach is denuded by high storm waves; heavier sediments remain on the beach. Load is bounced along the sea bed, e.g. small pieces of shingle or large sand grains. Currents cannot keep the larger and heavier sediment afloat for long periods. SALTATION Beaches can be attached to the mainland or detached. The side of the beach that is in direct contact with ocean waves is called the open side because it is open to the full force of the wind and waves. On barrier islands, the side of the beach that in on the lagoonal side is called the sheltered beach because it is sheltered from the most powerful waves. TRACTION Pebbles and larger sediment are rolled along the sea bed. Human activity also affects deposition such as taking home a bucket of sand or depositing sand in eroded beaches. Winds carry light particles and deposit them in the beach. Wind direction Wind „diręction LITHOLOGY Most of the material in a beach comes from the rocks in its immediate vicinity, while other sediments travel long distances. As a result, the type of rock and minerals present in every beach may vary. The most common mineral, however, is quartz", being able to survive long periods of weathering and transportation because of its durability. Quartz (SiO,) is light colored and translucent, resulting in colors ranging from white" or gray, to a yellow brown if oxidized. According to Paul D. Komar, a beach can be divided into thirteen parts The line of demarcation The sloping portion tying between a berm crest (sometimes the upper limit of wave swash at the exposed beach; the high tide) and the low-water mark of the run-down of the wave swash at low tide; includes the beach face and some of the flat portion of the beach profile below the beach The nearly horizontal portion of the beach or backshore formed by the deposition of sediments by waves. Some beaches have more than one berm at slightly different levels, separated by a scarp. between the water and water's edge. The zone extending landward from the sloping foreshore to the point of development of vegetation or change in physiography (sea cliff, dune field, etc.). Shoreline continues offshore Nearshore Volcanic rocks Usually produce black-colored beaches, though other colors may exist depending on mineral content. Some beaches in Guam, for example, are colored green due to the presence of olivine. Beaches may also... contain sediment from organic matter, such as shells or coral 10 11 Grain size on a beach is dependent on two things: a wave's energy and the size of the particles themselves. A wave with higher energy has the capacity to carry heavier particles, such as pebbles, while moving lighter grains to gentler water. Therefore beaches with stormy weather often have beaches with large particles, while gentler areas have Shorezone Beach or shore A nearly vertical escarpment cut into the beach profile by wave erosion. Its height is generally less than a meter. The scarp may be at the top of the beach face when erosion is OCcurring, but older scarps can be found on the berm due to former episodes of erosion. Shorerise Foreshore Backshore Surf zone: Berms, Seacliff Breaker Storm scarp Face Closure depth Terrace :/ Wave-cut Platform terrace Longshore trowgh Longshore bar beaches with finer particles." Storm bar Oftentimes, garbage ends up on a beach. While pollution destroys the pristine beauty of nature, they can sometimes bring about wonderful and unexpected results such as Glass Beach in Fort Bragg, California. This particular beach was formed after a nearby area was transformed into a dumping site back in 1949.12 As time passed, glass bottles were broken and dulled by the waves to form the beach we know today. The sloping nearly planar section below the berm, which is normally exposed to the swash of waves. The comparatively flat portion extending seaward from the inshore to the edge of the continental shelf; it is also used to refer to the water and waves seaward of the nearshore zone. The portion of the nearshore region in which bore-like waves occur following wave breaking. This portion extends from the inner breakers shoreward to the swash zone. The zone extending seaward from the foreshore to just beyond the breaker zone. Now, you know what a beach is. It's neither a bird, nor a plane, though it might contain sediments of both. And you really wouldn't want to try eating it. An elongated depression extending parallel to the shoreline and any longshore bars that are present, often representing the low point in the profile between successive bars. The portion in which the arriving waves become unstable and break. With uniform waves, such as generated in a laboratory wave tank, the zone may be reduced to a breaker line. On a wide, flat beach, secondary breaker zones may OCcur where reformed waves break for a second time. An underwater ridge of sand running roughly parallel to the shore, sometimes continuous over large distances, at other times having roughly even breaks along covered by the run-up of the wave swash and exposed its length. It may become exposed at low The portion where the beach face is alternately For a complete list of sources, go to http://bit.ly/1kgakQL Infographic prepared by Hans Maala, Danica Yasa and Kenneth Tabafunda as a requirement for Geology 11 under Sir Dominic Guballa, SY 2013-2014 by the backwash. Wave crests sheltred side Open side