According to theory, we forget memories because we don't use them and they simply fade away over time as a matter of normal brain processes.

The answer is "decay theory".

Decay theory recommends that memory blurs because of the unimportant entry of time. Data is along these lines less accessible for later recovery over the long haul and memory, and memory quality, wears away. When we gain some new useful knowledge, a neurochemical "memory follow" is made.

I'm going to go with 1,982 feet because of all of the ice.                                               ps its this is not the answer go with d 6,500.

Cextra