Complex sentence: The lava field now extends to 37 squared kilometres and it is estimated to amount to 0.4-0.5 cubic km of lava, making it a VEI 4 eruption.
Split into simpler sentences: The lava field now extends to 37 squared kilometres. It's estimated to amount to 0.4-0.5 km ^ 3 of lava, making it a VEI 4 eruption.