The mechanism is acretive action
The mechanism is gravity. Sir Isaac Newton developed a complete theory of motion, mechanics, that described the Earth-Moon binary system of mutual gravitational attraction. Because of the Moon tugging on the Earth's oceans, some of the Earth's angular momentum is transferred to the binary system's rotation and this causes the distance between them to increase. The Moon is gradually receding from Earth and is calculated that it would continue for about 50 billion years except for the Sun's radiation evaporating off the Earth's oceans in a couple billion years. Nothing for us to worry about for a while.