microfossil

A microfossil is a fossil so small that it usually has to be studied with a microscope. But their tiny size does not make them unimportant; these preserved remains are powerful tools for scientists studying Earth's history.

Microfossils are not simply broken bits of larger fossils. They can be the preserved remains of microscopic organisms, or very small biological structures such as pollen grains and spores. Common examples include single-celled algae such as diatoms, tiny shells from foraminifera and radiolarians, pollen, spores, and some kinds of bacteria. Many of these life forms lived in ancient oceans, lakes, and soils. When they died, their hard parts - often made of silica or calcium carbonate - could collect in mud or on the seafloor. Over long stretches of time, those sediments hardened into rock and preserved the microfossils inside.

Paleontologists, geologists, and climate scientists study microfossils to reconstruct past environments. The kinds found in a particular layer of rock can reveal water temperature, salinity, depth, nutrient levels, plant life, and broader climate conditions at the time that layer formed. They are also useful for dating rocks and for tracing changes in life on Earth over vast periods of time.

For example, oil and gas exploration has long used specific kinds of microfossils to identify the age and origin of rock layers that may contain useful resources. Microfossils are found in places ranging from deep-sea sediments to exposed rock along roadsides, giving us a window into worlds long gone. So when you think about fossils, remember that it is not only giant skeletons that tell Earth's story; some of the clearest evidence comes from remains almost too small to see.