Although people often believe that balanced rocks become stacked from falling on top of each other, in some cases water creates these beautiful rocks. The text states, "imagine a house built of strong bricks and held together by weak cement—bedrock often has these strong and weak parts, although they aren’t always visible." As rivers flow against the rocks, they take with them weak rock particles, while the stronger rocks that remain begin to look stacked. Many scientists theorize that this took place during the last ice age.