All the major land masses were collected together in the super-continent Pangaea. At the end of the period, the greatest flood basalt lava flows in the Phanerozoic raised world temperatures, and damaged the environment. These formed the extensive "Siberian traps". The causes of the Permian/Triassic extinction event are not yet agreed between scientists. Trilobites, once a dominant life-form in the ocean, became extinct, together with 90% of all marine species.