Complex sentence: During the Jurassic Period (150), Cimmeria finally collided with Laurasia and stalled, so the ocean floor behind it buckled under, forming the Tethyan Trench.
Split into simpler sentences: During the Jurassic Period (150), Cimmeria finally collided with Laurasia. There it stalled, the ocean floor behind it buckling under, forming the Tethyan Trench.