中文摘要：

本文通过资料分析和模型计算,得到地球自转速率长期减慢趋势和周期波动规律的形成原因.潮汐摩擦是地球自转减慢的主要因素,重力分异和圈层角动量交换是地球自转周期变化的主要因素,重力分异造成的地球各圈层差异旋转是地壳自转变化先慢后快的特殊因素.重力分异将一个均匀的自转地球变为分层的差异旋转地球,在质量向地心集中的同时,自转动能也向地核集中,使地壳和地幔自转变慢,使地核自转变快.圈层角动量交换将地球自转动能变为热能,积累在核幔边界,使地壳和地幔自转变快,地核自转变慢.核幔边界积累的热能周期性使外核热膨胀,为热幔柱和火山活动提供了能源和动力,火山活动高峰对应地球自转加快是证据.计算模型表明,地球自转速度变化的规律和历史记录证明重力分异和圈层差异旋转是地壳运动的主要动力,受地球自转速度变化的约束,地球体积不会有较大的胀缩,国内外测量结果证实了这一结论.

英文摘要：

Based on the data analysis and model calculation, the authors obtain the forming reason of earth＇ s rotation rate slowing down in long-term and periodic fluctuation laws. Tidal friction is a major factor of earth＇ s rotation slowing down, the gravitational differentiation and earth differential rotation are the major factor of earth＇s rotation cycle change, earth differential rotation which caused by gravitational differentiation is the special factor of earth＇s rotation change from slow to fast. Gravitational differentiation divides a uniform rotational earth into layer differential rotation one, when the earth mass is gradually concentrated to earth core, the kinetic energy of earth＇s rotation is also to the core, which makes crust and mantle rotation decrease and core rotation increases. Circle layer angular momentum exchange makes kinetic energy of earth＇s rotation into heat energy and accumulates in the core- mantle boundary, which make crust and mantle rotation increase and core rotation decreases. The energy periodic makes thermal expansion of outer core, which provides energy and power for thermal mantle plumes and volcanoes, the longest sustained warm period in ancient centuries occurred in the Gretaceousperiod, following the strongest eruption of volcano and high speed of the earth rotation. The calculation model shows that the laws of earth＇ s rotation rate change, gravitational differentiation and differential rotation are the major power for erustal movement, earth＇s volume constrainted by the rotational rate change can not swell-shrinking greatly, the measurement results at home and abroad confirm the conclusion.