Earth may be considered a huge machine driven by two engines, one internal and one external. These heat engines
convert heat energy into mechanical energy. Precipitation resulting from the external heat engine’s weather systems
supplies moisture to Earth’s surface that contributes to the weathering of rocks. Running water erodes mountains
that were originally uplifted by Earth’s internal heat engine and transports sediments to other locations, where they
are deposited and may undergo the processes that transform them into sedimentary rocks.