Earth's terrestrial topography evolves in response to the interaction of tectonics, climate, and lithology. Recent discoveries suggest that the grain size of sediments produced on hillslopes and transported through river networks is key to understanding these interactions. Hillslope grain size varies systematically with erosion rate and residence time, the degree of chemical and physical weathering, and the fracture density and susceptibility to weathering of rock. Variations in initial grain size strongly influence the spatial evolution of grain size distributions as particles mix and wear during downstream transport through channel networks. In rivers, the size and flux of the coarse fraction of the sediment load control the rate of incision into bedrock and thus govern channel slope and ultimately the relief of actively eroding landscapes. These relationships suggest that a primary way that tectonics, climate, and lithology influence landscape evolution is through their controls on sediment grain size. ▪Recent research reveals the central role of sediment grain size in controlling bedrock river morphodynamics, linking grain size to channel slope and topographic relief.▪Tectonics, climate, and lithology govern the size of sediments produced on hillslopes; hence, grain size mediates their influence on landscape evolution.▪Feedbacks linking sediment grain size, topography, weathering, erosion, and sediment transport provide new opportunities for advances in Earth surface science.

中文翻译：

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 景观中的颗粒大小


地球的陆地地形是响应构造、气候和岩性相互作用而演变的。最近的发现表明，在山坡上产生并通过河流网络运输的沉积物的粒度是理解这些相互作用的关键。Hillslope 颗粒尺寸随侵蚀速率和停留时间、化学和物理风化程度以及岩石的破裂密度和风化敏感性而变化。初始晶粒尺寸的变化强烈影响晶粒尺寸分布的空间演变，因为颗粒在通过通道网络的下游运输过程中混合和磨损。在河流中，沉积物负荷的粗部分的大小和通量控制着切入基岩的速度，从而控制河道的坡度，并最终缓解活跃侵蚀的景观。这些关系表明，构造、气候和岩性影响景观演变的主要方式是通过它们对沉积物颗粒大小的控制。▪最近的研究揭示了沉积物粒度在控制基岩河流形态动力学中的核心作用，将粒度与河道坡度和地形起伏联系起来。 ▪因此，颗粒大小介导它们对景观演变的影响。▪将沉积物颗粒大小、地形、风化、侵蚀和沉积物运输联系起来的反馈为地球表面科学的进步提供了新的机会。