Earth experienced a period of intense, large-scale volcanism during the early Aptian. Around that time, it also experienced widespread ocean deoxygenation during the Oceanic Anoxic Event 1a (OAE1a) as well as the onset of a period of unusual stability in Earth's magnetic field, known as the Cretaceo us Normal Superchron (CNS), which lasted about 38 million years. ...read more read less