Image of the month

Coccoliths

April's image shows a group of coccoliths (coloured blue in this image) found in a sample of marine sediment from the seafloor.  Coccoliths are plates of calcium carbonate produced by single–celled algae, know as coccolithophores, which float in the upper layers of the worlds oceans.  Living coccolithophore cells are surrounded many overlapping coccoliths, which together form a shell, or coccosphere.  When the cell dies and sinks to the seafloor the coccosphere breaks up into the individual plates seen here.  Over millions of years the accumulation of individual coccoliths can lead to the formation of chalk deposits.  This process, followed by a period of geological uplift, produced that chalk bedrock that occurs over much of southern England, including the white cliffs of Dover.

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