Beached Sea Garden in Greenfield, NY

Submitted by Deborah Cramer

Beached Sea Garden in Greenfield, NY
Fossils of microbes that put oxygen into Earth’s atmosphere
Photo © Eric Straffin, Edinboro University of Pennsylvania

Unlike its neighbors Venus and Mars, Earth’s atmosphere is rich in oxygen. Four billion years ago, when the planet was young, its atmosphere held little. Photosynthesis, which evolved in the ocean, made the difference. During the Archean era, tiny marine microbes using sunlight to split apart water molecules and make carbohydrate, gave off oxygen as waste. Over millions and millions of years it filled the atmosphere, making possible the rise of large animals.

Today, the oxygen in every other breath you take is produced by invisible plants floating in the sea.

New York State was near the equator 490 million years ago, during a time known as the Cambrian. A tropical sea stretched halfway across the continent. In its shallow waters were large reefs built of photosynthesizing microbes. The microbes – cyanobacteria – lived in mats built up into layers of rock – stromatolites. In the woods of rural Greenfield, you can still see their remains; they resemble slices of cabbage.

Greenfield isn’t the only place to see fossils of Earth’s first photosynthesizers. Check out their older cousins in Australia’s Karijini National Park and their living descendents in Hamelin Pool in Shark Bay, Australia.

References and more information

Lester Park: New York State Museum

Map of ancient sea in New York 490 million years ago – Cambrian

Early earth: Smithsonian Ocean: Our Water Our World

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