Earth history

Annual growth rings in sample of Irish bog oak
Annual growth rings in sample of Irish bog oak

The Earth keeps a record of itself. Rocks of different origins and ages present themselves for inspection. It accumulates layers of sediment (soil/mud/sand/silt) on land and under seas, oceans and lakes – these contain bones and bits of dead plants and insects. The poles collect layers of snow and ice containing tiny particles and trapped bubbles of gas. The annual rings of trees, those still living and those preserved in peat bogs, reveal periods of faster and slower growth. Like natural tape recordings, long cores drilled out of some of these materials reveal a continuous succession of changing conditions, environments and patterns of life. Since the late 1940s, new methods of dating rocks, mineral grains and dead organic matter (based on steady rates at which radioactive elements decay) have allowedscientists, many of them British, to date bits of the Earth, and events in Earth history, for the first time. Some Scottish rocks are 2.8 billion years old, among the oldest on the planet. Globally, trees suffered around 540 AD, suggesting a catastrophic event. Arctic beetles were living in Wales 13,000 years ago. And so on. In reporting on the history of the Earth, scientists often find themselves at odds with other, older, biblical stories of Creation.

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