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USGS Geology in the Parks


Radiolarians are microscopic, single-celled animals. Although they are closely-related to the blob-like amoebas you see in high school biology class, radiolarians are exceptionally elegant creatures. Radiolarians have elaborate skeletons made mostly of silica. They extract the silica from the sea water they live in. They catch their food as they float in the ocean currents by sticking long, sticky, finger-like projections called pseudopodia through the many holes in their skeleton.

After they die, their skeletons may sink to the ocean bottom. If a thick enough layer of skeletons accumulates, they may eventually harden to form chert, a very hard, often colorful, rock.


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