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Why is the deepest part of a rift valley not always in the center?

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tectonic basins and rift valleys Escarpments of the Great Rift Valley rising above the plain north of Samburu Game Preserve, central Kenya. Beisa oryxes graze in the foreground.

While rift valleys are often envisioned as symmetrical troughs with a central floor, they are frequently asymmetrical in practice. The deepest part of a rift valley is not always at its center because of the specific geological processes involved in their formation.1

Many rift valleys are characterized by one steep wall formed by major faulting, while the opposite side is formed by the flexing and tilting of the lithosphere rather than a major fault. In these cases, the valley floor rotates or tilts toward the primary fault, causing the most rapid sinking—and thus the deepest point—to occur along that margin rather than in the middle.1

Additionally, the edges of these valleys often consist of multiple steps or tiers, where smaller inner blocks drop relative to their neighboring outer blocks. This complex, stepped topography means that the lowest elevation is determined by the specific displacement of these individual crustal blocks rather than a uniform central depression. Famous examples of this asymmetry include Death Valley and the Baikal Rift, both of which feature a steep margin and a gentler, tilted side.1