Reef - Gansho (English spelling)

Japanese: 岩礁 - がんしょう（英語表記）reef

A type of reef. Rocks on or near the sea surface, shallow waters less than 20 meters deep that are dangerous for ship navigation. They are often found around rocky coasts and volcanic islands. The former are shallow waters that have been eroded by breaking waves and left offshore, while the latter are parts of volcanic islands that have been raised by undersea volcanoes. They are classified according to their state of exposure to the sea surface, and include above-water rocks that remain above the sea surface even at high tide in spring and autumn when the tidal range is greatest, dried-up rocks that are submerged at high tide but above the water surface at low tide, washed-out rocks that appear when waves are high, and dark rocks that are below the water surface even at low tide. Reefs can change the direction of coastal currents and cause waves to break. Animals such as gastropods and sea anemones live on the upper part of the reef. Seaweeds such as Ecklonia cunea grow thickly on the lower part, and they are habitats for crustaceans such as crabs and shrimp, mollusks such as octopus, and shellfish such as abalone and turban shells, as well as nurseries for young fish. Coral reefs develop in the clear waters of low latitudes. Shallow waters formed by the accumulation of sand and mud are called shoals. Coral reefs and shoals, like rock reefs, can impede the navigation of ships.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

礁の一つ。海面あるいは海面近くにある岩で，船舶の航行に危険となる 20m以浅の浅瀬。ごつごつした岩からなる磯海岸や火山島の周辺で多く見られる。前者は磯が砕波により浸食され沖側に取り残された浅瀬で，後者は海底火山により隆起した火山島の一部である。海面への露出状態によって区別され，干満差が最も大きい春・秋の大潮の満潮時でも海面上にある水上岩，満潮時に水没するが干潮時に水面上にある干出岩，波浪が高いときに現れる洗岩，干潮時でも水面下にある暗岩などがある。岩礁は沿岸流の向きを変え，波を砕けさせることがある。岩礁地の上部には巻貝類やイソギンチャク類の動物が生息する。下部にはカジメなどの海藻が生い茂り，カニやエビなどの甲殻類やタコなど軟体動物，アワビやサザエなど貝類の生息場，稚魚の成育場でもある。低緯度の澄んだ海水域ではサンゴ礁が発達する。砂や泥などが堆積し浅瀬となっている場を瀬と呼ぶ。サンゴ礁や瀬も岩礁同様，船舶の航行を妨げる。

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