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Why do plateaus usually have low relief despite their high elevation?
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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.
Plateaus exhibit low relief despite their high elevation because of the specific geologic processes that form them, which often preserve or create flat surfaces during uplift.12
The reasons for this characteristic flatness vary by formation type:
- Thermal Expansion: When the lithosphere is heated by upwelling material from the asthenosphere, the surface can rise uniformly. If the land was already a low-relief area before this uplift, it tends to remain relatively flat as it rises.2
- Sedimentary Stability: In some cases, such as the Colorado Plateau, the area consists of erosion-resistant sedimentary rock that has undergone minimal deformation for millions of years. When these stable, flat layers are lifted, they maintain their remarkably level surface.2
- Volcanic Activity: Extensive lava flows, known as flood basalts, can bury preexisting terrain. These flows spread over long distances, creating a very flat top surface that defines the plateau.2
- Internal Drainage: Plateaus formed by crustal shortening can develop when debris fills the basins between mountain ranges. This creates broad, flat valleys that form the plateau surface.2