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Lahars move rapidly down valleys like rivers of concrete. If you are on the floor of a valley that leads from a volcano and become aware of an oncoming lahar, seek high ground. Lahar is an Indonesian term that describes a hot or cold mixture of water and rock fragments that flows down the slopes of a volcano and typically enters a river valley.
Believe it or not, tanks can actually move at about 25 miles per hour on flat terrain and up to 45 miles per hour on roads! Some tanks have even gone as fast as 60 to 70 miles per hour for short periods of time. Tanks aren't really built for speed, though.