Iron-sand
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Because they are made of black volcanic sand rather than white coral sand or white quartz/limestone sand. However, Japan has also many white sand beaches, which are made of white coral sand (southern islands) and white quartz/limestone sand (peninsulas on mainlands). White sand beaches in Japan: http://www.flickr.com/photos/ippei-janine/sets/72157600321338295/ There are also black sand beaches in volcanic countries such as Hawaii and Iceland.
The beaches with black sand are volcanic in origin.
The city of Constanţa, because it have beaches at the Black Sea.
for its beaches
"The Bulgarian Black Sea Coast (Bulgarian: Черноморие, Chеrnomoriе) covers the entire eastern bound of Bulgaria stretching from the Romanian Black Sea resorts in the north to European Turkey in the south, along 378 km of coastline. White and golden sandy beaches occupy approximately 130 km of the 378 km long coast."
Jamaica and the smaller surrounding islands were formed from an arc of ancient volcanoes. Mountains cover the eastern part of Jamaica, while central Jamaica is valleys and plateaus. The coastal plain is flatter, gently sloping land. The northern coast offers calm seas and white sandy beaches, while the southern coast has black, sandy beaches.
Volcanic beaches are black because the sediments on the beach come from volcanoes. In other words, if a beach is black, that means that there was or is volcanic activity in the area.
It depends on the soil. There is red clay soil, brown sandy soil, and dark brown/black earthy soil. There are white sand beaches, black sand beaches and there are even a few beaches with green sand.
Beaches form when tiny bits of rock that have been eroded by the action of the waves wash up on shore. They are different because they tend to be composed of different types of sand (rock bits). For example, beaches formed mainly of lava rock will have black sand, while other beaches may be white, pink, or tan.
Black sand is sand that's been turned a black color either by a glossy partly-magnetic mix of sands (usually fine), or by tiny fragments of lava.Some gold and white beaches can also contain black sand, typically after storms have sorted out grains where heavier, darker particles remain on the surface.There are many black sand beaches around the world. Prince William Sound, in Alaska, and Lost Coast, California, both have black sand beaches named Black Sand Beach. Hawaii has Kehena Beach, Oneuli Beach, Polulu Valley Beach and Kaimu Beach. Maui hosts Oneuli Beach, Honokalani Black Sand Beach and Waianapanapa Black Sand Beach. Finally, Vik Beach in Iceland has some breathtakingly blue water surrounded by eroded rock formations beyond a beach of black sand.For more black sand beaches, try a Web or Image search on Google or your favorite search engine for black sand beach. You'll be stunned by some of the amazing photos.
Polish beaches are sandy, yes, but they are not on the Black Sea. It's Baltic Sea.