Complex sentence: The Island Park Caldera is one of the world's largest calderas at 18 miles (29 km) long and 23 miles (37 km) wide, in eastern Idaho just to the southwest of the Yellowstone Caldera.
Split into simpler sentences: The Island Park Caldera is one of the world's largest calderas at 18 miles (29 km) long and 23 miles (37 km) wide. It is in eastern Idaho just to the southwest of the Yellowstone Caldera.