New Haven, Conn. — The murky world at the bottom of the oceans is now a little clearer, thanks to a new study that tracks the evolution of marine sediment layers across hundreds of millions of years.

It is a story of world-building on a grand, yet granular, scale, accomplished by a succession of marine animals that burrowed and tunneled their way through heat and cold, species expansions and mass die-offs. Scientists call the process bioturbation — the excavation and mixing of sediments and soils by burrowing animals, particularly for shelter and sustenance.

“Bioturbation is one of the most important forms of ecosystem engineering today, both in the oceans and on land,” said Lidya Tarhan, assistant professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences, and lead author of the study published in the journal Science Advances.

Recent study at UC San Diego is the first detailed assessment of companies offering school-based online surveillance services such as social media monitoring, student communications monitoring and online activity monitoring to middle and high schools.