Maximum estimated time before the moon Phobos collides with Mars. According to Christopher R. Scotese, the movement of the San Andreas Fault will cause the current locations of Los Angeles and San Francisco to merge. The Californian coast will begin to be subducted into the Aleutian Trench. Africa's collision with Eurasia closes the Mediterranean Basin and creates a mountain range similar to the Himalayas. The Appalachian Mountains peaks will largely erode away, weathering at 5.7 Bubnoff units, although topography will actually rise as regional valleys deepen at twice this rate.