Answer:
A lot of things that happen during geologic processes, such as the cooling and crystallizing of a magma, the erosion of landmasses, the transport of sediment by rivers, the filling up of ocean basins, all these processes can be observed in action in nature or in laboratory analogues (melting and crystallizing of rock in the lab, crystallization of salt from solution, weathering of building stones, floods of rivers, erosion of river banks, the filling in of embayments on the Mississippi delta within some decades). We are reasonably adept at manipulating the physical world in terms of spatial relationships and physical parameters (temperature, pressure), but one dimension of the physical world has so far escaped our manipulative powers TIME . Nonetheless, the writers of science fiction novels routinely use time travel to get themselves and their heroes/heroines out of trouble.
