Competition exits not only in organism and human society, but in geomorphic open system, evolution of many landforms can also be analogized to competition. The Fen River and the Jinshan Yellow River ( east reach of the square bend shape Yellow River around the Ordos block in North China) on east and west sides of the Liiliang Mountains are taken as an example of fluvial competition in this paper. Comparing the Yellow River,the Fen River is only its tributary. However,based on our very detailed field investigation( more than 400 sites) on deposition from Late Neogene to Quaternary and chronological study including magnetostrigraphy, loess serigraphy and OSL dating along the Jinshan Yellow River, and incorporated with former research on both the Jinshan Yellow River and Fen River,it is concluded that before connection of the Hetao Basin to the north,the Jinshan Yellow River and ancient Fen River had shared similar features in flow direction, length and probably in discharge. They could be considered as "twins" originating from intensive uplift of the Liiliang Mountains. They flew from north to south on east and west sides of the mountains respectively into the Houma-Yuncheng Basin,the local base level. Experiencing two stages of Pliocene broad valley and Early to Middle Pleistocene deep gorge,in Late Pleistocene,the Jinshan Yellow River had eroded headward and cut into the ancient Great Hetao Lakes,I. E. Hetao Basin in the north. Sharp increase in both discharge and length of the Yellow River leads to rapid down cutting and development so as to " win" in the competition with the Fen River,which had been degraded into a tributary of the Yellow River. The near 100 year debates on the forming ages of the Jinshan Yellow River, I. E., Pliocene, Early Pleistocene and Late Pleistocene, actually came from the conglomerate along the Jinshan broad valley, the highest strath terrace along lower to middle reach of the Jinshan Gorge, and the highest strath terrace along the upper reach of the gorge north of Hequ, respectively, representing the three stages of the Jinshan Yellow River evolution. They do not conflict. Most scholars consider that the Yellow River was formed by connection of various basins along the course. But only are the Hetao and Houma-Yuncheng basins farthest separated ( about 700km ) so as to become difficult and key areas for connection of the about 5700km long Yellow River. From the discussion we can partly understand the reason why the Jinshan Yellow River is latest connection reach of the whole river. Competition causes survival of the fittest, surpassing of the latter,and different results from one cause,making complicated evolution courses of landform. Big river is not necessarily old one, and vice versa. Thus, broadening and liberating our minded, and avoiding conventional pattern sticking, are very important in geomorphic study. Only in this way can we better explain landform evolution and understand origin of complex landforms so that we can shorten the distance to the truth.%竞争不但存在于生物界与人类社会,在开放的地貌系统中,地貌发展也存在可以类比于竞争的现象.分布于吕梁山东、西两侧的汾河和晋陕黄河的发展演化即为其例.汾河与晋陕黄河都是吕梁山强烈抬升而诞生的“双胞胎”,分别在吕梁山东、西两侧由北往南流入侯马-运城盆地.盆地水位是两河下切的侵蚀基准面.在经历了上新世宽谷、早-中更新世峡谷阶段之后,晋陕峡谷终于在晚更新世溯源沟通了北面的河套古大湖,因流量急增,源头加长,晋陕峡谷迅速深切、快速发展,在与汾河的竞争中“获胜”,使汾河退居到支流的地位.前人关于晋陕黄河形成于上新世、早更新世和晚更新世等3种不同观点实际上是晋陕黄河形成演化的3个不同阶段,并不矛盾.竞争导致后来居上,产生一因多果,使地貌发展复杂多变.大河不一定老,小河不一定新.地貌学研究必须开阔思路,切忌墨守成规,才能更好地认识地貌演化的规律和复杂地貌的成因,从而缩短接近真理的路程.
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