Right from the beginning of Lord of the Flies, the reader has an image of the scar; an indelible mark left on the landscape in this seeming paradise. It is "smashed into the landscape" and already foreshadows events that may follow as basic instinct is unleashed with no "grown ups" to moderate behavior "smashing" into everything, leaving behind a scar that will be visible forever. There is also the scar that will be left in Ralph's heart as he "weeps for the end of innocence."
“Beyond falls and cliffs there was a gash visible in the trees; there were the splintered trunks and then the drag, leaving only a fringe of palm between the scar and the sea”
The image of the scar is unmistakable and the metaphor extended. The "fall" is of course the fall of the landscape but when a person falls it will leave a "gash." The boys are taking in everything they see and only stop to reflect for a moment on Jack's comment "that's where we landed." The "scar" is seen clearly from their position. Things have already changed since their arrival.
The apparent violence that accompanied the landing - which must have been rough- causes "splintered trunks" and "drag." This imagery allows the reader to contemplate as it slows down the action, even if only briefly before the boys claim "their island; "it's all ours."