西藏可能曾存在一个面积达15万平方公里的“古大湖”，当古大湖的湖水流失时，地壳会因为载荷减少而产生形变，造成岩石层的回弹和倾斜，考察因此而产生的湖相沉积物间不整合角能为古大湖的研究提供新的佐证。本文通过简化的力学模型计算证明，湖水减少引起的湖底倾斜量微不足道、难以观测，总的变形量也不大，仅数十米，但这种抬升速率可能极其迅速，其环境、气候、地貌等方面的效应值得进一步研究。

Some researchers suggested that there was an ancient large lake covered about 15,000,000 square kilometers in Tibet, and when the water flew away and the lakes dried up, the crust would be deformed because of the unloading. Therefore, the angle of unconformity between lake sediments may provide new evidences for further research on the lake history. In this paper, we use a simplified mechanical model to calculate the lake-bottom deformation induced by unloading of reduction of lake water. We found that the tilt of lake bottom is negligible and difficult to be detected in the field. The maximum deflection is also quite limited, only about tens of meters. However, the uplift rate may be very fast, and its effects on environment, climate and physiognomy are worth to be further studied.