Complex sentence: The Adirondacks do not form a connected range such as the Rocky Mountains of the Western United States but are an eroded dome consisting of more than 100 peaks, either isolated or in groups, often with little apparent order.
Split into simpler sentences: The Adirondacks do not form a connected range such as the Rocky Mountains of the Western United States. They are instead an eroded dome consisting of many peaks, either isolated or in groups, often with little apparent order.