Foram is the shortened name for a foraminiferan, a tiny protozoan, says Pat Morris, that's about 0.5 and 1 mm long.
Foraminierans float in the marine plankton and their shell come in many shapes; for example, they may resemble tiny molluscs or bean pods. When the animals die, their perforated shells sink to the seabed.
Forams were so abundant about 100 million years ago that their remains built up in thick layers, which later became compressed to form rock. England's chalk hills are made of foraminiferan rock.
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Forams are significant for two other reasons. Their distribution and composition give us clues about past climates, and, together with other planktonic deposits, they are a major component of oil.