Does a delta change over time?

Delta is typically used to symbolize "change in" a definable quantity; e.g., "delta t" could symbolize "change in time", where t means time. Since delta, used this way, is really a math term, such as capital sigma is the "sum as" term, then used this way, no it does not change. However, if you are using delta as a variable, the way that you can use any symbol as a variable, then yes, it can change.

In geology a delta is constantly changed by the action of the sea and the water diversion from human industry/deforestation, and rubbish being washed down stream