Cause..... The finding of gold made many people move towards the west, and they also brought their beliefs about slavery. Soon, they asked for ratification (when they reached the requirement) and had to choose to be either a free or slave state, which would have offset the balance between the amount of free and slave states.
Because... Many people wanted to become rich, and so they would risk everything they had and their lives to get their chance at a new life and to strike it rich.
Effect... As more people wanted to join the statehood, they had to choose either to register the state as a free-state or slave-state. This ended up effecting how the South and North felt, and eventually help lead the nation into a civil war. This then led to the end of slavery and the beginning of the Reconstruction Era.
hope this helps