Earth’s extensive igneous provinces. (a) Plateau basalts form large igneous provinces across the globe. Many are ancient and inactive. The largest known is the Ontong Java Plateau, which covers nearly 2 million km 2 (0.8 million mi2 ) on the Pacific Ocean floor. Black dots are areas of ancient volcanism along continental margins. (b) In the foreground are plateau (flood) basalts characteristic o..
