How does Heart of Darkness depict a journey from innocence to experience?

One way in which Heart of Darkness depicts a journey from innocence to experience can be seen in Marlow.

Prior to undertaking his mission, Marlow displays innocence.  Marlow shows innocence with his passion for maps, his love of exploration, and the desire to travel into the heart of Africa.  These are pure expressions.  In Marlow's mind, there is limitless hope and optimism in what lies ahead. Over time, though, Marlow begins to show the signs...

One way in which Heart of Darkness depicts a journey from innocence to experience can be seen in Marlow.

Prior to undertaking his mission, Marlow displays innocence.  Marlow shows innocence with his passion for maps, his love of exploration, and the desire to travel into the heart of Africa.  These are pure expressions.  In Marlow's mind, there is limitless hope and optimism in what lies ahead. Over time, though, Marlow begins to show the signs of experience. He becomes frustrated with the lack of access to proper equipment as well as the excessive materialism that guides so much of the Company's work in the Congo.  

Marlow's journey to experience is clearly evident in his perception of Kurtz. Marlow sees Kurtz as one who used to possess "the magnificent folds of eloquence," but now only holds "the barren darkness" within his heart. Marlow sees how temporary "images of wealth and fame" have become.  In Kurtz, Marlow recognizes how experience supplants innocence. 

The "heart of darkness" is a realm where Marlow understands the painful condition of experience.  Marlow's voyage haunts him, causing him to fully understand that within all hope lies the terror of reality.  It gnaws away at who we wish to be and replaces it with who we truly are.