Some of the resulting magma erupted to form a lofty volcanic arc, like the present-day Andes Mountains of South America, but the larger part of it remained within the crust, forming great overlapping chambers.
(Some of the resulting magma; erupted; ) (Some of the resulting magma; to form; a lofty volcanic arc, like the present-day Andes Mountains of South America) (the larger part of it; remained; within the crust)
Some of the resulting magma Some of the resulting magma the larger part of it
erupted to form remained
a lofty volcanic arc, like the present-day Andes Mountains of South America
within the crust