Complex sentence: The Kansan Glaciation is generally taken as covering the period between 410,000 and 380,000 years before the present, though with the increasing evidence that glacial "maxima" are actually quite short, its peak is not clearly known.
Split into simpler sentences: The Kansan Glaciation is generally taken as covering the period between 410,000 and 380,000 years before the present. However, with the increasing evidence that glacial "maxima" are shorter than previously thought, its peak is not clearly known.