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How can a plateau be surrounded by mountains instead of escarpments?

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plateau The Columbia Plateau is uniformly covered with basaltic lava flows and spans an area of about 100,000 square miles in Idaho, Washington, and Oregon.

A plateau is typically defined as an extensive area of flat upland, often bounded by an escarpment. However, plateaus can be surrounded by mountains rather than steep slopes when they are formed through the process of crustal shortening.12

In these instances, the plateau is essentially a mountain range that has been buried in its own debris. As tectonic forces cause the crust to thicken and create mountain belts, internal drainage patterns develop where streams and rivers transport eroded material into the basins or valleys between the peaks. Over time, this sediment fills the valleys, creating a remarkably flat surface that is enclosed by the surrounding mountains.1

These plateaus are most common in arid climates where erosion is slow, allowing the flat, sediment-filled basins to persist. Prominent examples of such plateaus, which are integral parts of mountain belts, include the Altiplano and the Plateau of Tibet.132