All landforms change over time. First, plates of the Earth's crust collide to form a mesa. Then over time mesas get eroded. Harsh storms and wind make the lower part of the mesa, which is softer, cave in. Then, with nothing to support it, the cap rock falls down. Although mesas get smaller, they shrink only a fraction of an inch a year. Every one million years a mesa will shrink 500 feet. As the sides get smaller, the top gets shorter. Eventually it gets small enough to be considered a butte.
How a Mesa Changes Over Time