By Science News
![Rocks in the Jack Hills of Western Australia hosted zircon crystals that contain tiny mineral inclusions, such as the one denoted by the arrow in the false-color inset. The zircons and inclusions are more than 4 billion years old and contain evidence suggesting an early start for tectonic activity on Earth.](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2008/11/9284.jpg?resize=300%2C243&ssl=1)
Evidence included
Zircons hint at early tectonic activity, life
Two analyses of tiny mineral bits that crystallized during the Earth’s formative years have provided new insights into the planet’s earliest days.
One study of mineral inclusions in zircons from the Jack Hills of Western Australia hints that the crystals formed at depths of around 25 kilometers and at temperatures of about 700° Celsius. Those findings, in turn, suggest that plate tectonics had already begun on Earth between 4.19 billion and 4.02 billion years ago, less than 600 million years after the planet first coalesced (SN: 1/3/09, p. 10).