Toward the end of chapter 11, Roger purposely dislodges a giant boulder from the top of Castle Rock and rolls it directly towards Piggy. The boulder ends up hitting Piggy and kills him instantly. Golding writes,

The rock struck Piggy a glancing blow from chin to knee; the conch exploded into a thousand white fragments and ceased to exist. (141)

The sentence literally describes how the boulder smashes into Piggy and simultaneously destroys the conch. Throughout the novel, Piggy represents rational, intellectual individuals, who rely on the rules and institutions of society to protect them. Individuals like Piggy cannot survive in a brutal, savage environment, where only the strongest, most aggressive people survive.

The conch is also symbolically significant and represents order, democracy, and civility. Piggy's brutal death and the simultaneous destruction of the conch symbolically represent a point in the novel when savagery reigns supreme, and there is no longer a chance of establishing a civil society on the island. Following Piggy's death, Ralph is forced to flee as Jack commands his tribe of savages to hunt and murder Ralph.