sandy beach

Article

August 8, 2022

A sandy beach (sunahama) is a boundary area between land and water, where sand is deposited by waves and wind.

Overview

The beach is the interface between water and land, consisting of sediments such as sand, mud, shells, and organic deposits (plant remains) moved by waves and wind. On coral reefs, hermatypic corals are most active in fresh seawater, and therefore develop in shallow areas facing the open ocean. Near the coastline, instead, it becomes a sandy beach where dead coral and fragments of coral skeletons are deposited. The sandy beach, which is derived from coral, contains a lot of calcium carbonate and is characterized by its whitish color. Special sand types include: Singing sand (singing sand) There is a sandy beach that makes sounds when you walk on it. Such beach sand is called singing sand or singing sand. star sand (star sand) It is the shell of a foraminifera. red sand beach Iron oxide pink sand beach found in Prince Edward Island, Canada A sandy beach of broken coral found in Bermuda, the Bahamas, etc. orange beach A mixture of shredded shells, limestone, and volcanic eruptions found at Ramla Bay Beach, Sardinia, Gozo, etc. black sand beach black sand beach of basalt sand in hawaii green sand beach Hawaiian olivine green sandy beach

Beaches and Sandy Beaches

Since sand is a particle that can be easily moved by waves, we should think of a beach made of sand as a beach where sand is carried and deposited. Places facing the open sea that are hit by strong waves tend to become rocky shores, and inner bays tend to become tidal flats due to accumulation of mud.

Terrain

A sandy beach is formed where sand accumulates, but it extends along the coastal currents that carried the sand, and in some cases the tip protrudes away from the shore. This is called a sand spit. When the tip of a sand spit touches land, it is called a sandbar. An island that is connected to land by a sandbar is called a land-tied island. When hills are formed by the wind, they are called sand dunes. When it looks like a bank, it is called a beach bank.

As a biological environment

Sandy beaches are difficult environments for organisms to live in because the sand, which is the substrate, is not fixed and changes with the wind and waves. Therefore, it has a unique biota. In particular, sea turtles lay their eggs only on sandy beaches. Windbreaks are sometimes constructed to protect coastal hinterlands, as sand is moved by the wind. On the other hand, although it is an environment where the surface is easy to deform and move, human disturbance also has different effects. For example, it is known that when a four-wheel drive vehicle enters a sandy beach, deep ruts are left behind, and this has a great impact on beach plants and baby sea turtles. Since 2001, Japan has taken measures such as banning vehicles from entering sandy beaches in principle due to the revision of the Coastal Law.

Beach Issues

It is used to reduce the amount of sediment runoff due to river bank protection, to reduce the amount of sediment runoff due to the accumulation of sediment on the bottom of the dam lake when a dam is built in the river, and when making concrete such as sand and gravel. Aggregate collection progresses and the absolute amount of sand decreases. For these reasons, the amount of sand flowing into the sea is decreasing, and the phenomenon of coastline erosion on sandy beaches in various places can be seen. As a countermeasure, install wave-dissipating blocks and transport from other places.