Complex sentence: This is based both on the extent of uplift, which was recorded along the coast of Burma from Foul Island to Ramree Island, and the area of subsidence around Chittagong, further north.
Split into simpler sentences: This is based on the extent of uplift, which was recorded along the coast of Burma from Foul Island to Ramree Island. The greater length incorporates the area of subsidence around Chittagong, further north.