Complex sentence: It is a geologically independent basin from its neighbor basins; the Simeulue Basin to the north, and the Mentawai and Enggano Basin to the south.The Nias Basin spans ~ 250 kilometer length-wise, and ~ 100 kilometers width-wise.
Split into simpler sentences: It is a geologically independent basin from its neighbor basins; the Simeulue Basin to the north, and the Mentawai and Enggano Basin to the south. In terms of size, the Nias Basin is ~ 250 kilometer length-wise, and ~ 100 kilometers width-wise.