| 發表者 | 討論主題：hRRkkuVVlMamhRxLwYq | ||
| Ethan | 8/6/2014 2:18:35 AM [瞼羸瞼?]•[繡礙簞T繚~]•[翹礙織簷] | 
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| Your account's overdrawn we write college papers Simple radio waves can map the bedrock by travelling at frequencies known to travel through ice. The amount of time it takes the waves to traverse the ice and then bounce back off the rock below tells the scientists how deep the canyon is. | |||