[need] NAND Write & Erase..why Erase of PAGE not possible..why BLOCK Erase

Hi.
Can anyone explain why ERASE of whole BLOCK is performed but WRITE can be performed to PAGE.
Why ERASE of PAGE is not possible ?
Is there any Physics behind this phenomenon.
thanks

See as per I know pages is also made up of block.....and you have block level control for erase in many flash memories....but when you want to do the write you need to specifiy the address ....if a write in continous mode....select the address in the sequential manner...where it may be from one block to another ....where as erase operation is only restracted to place zero....block erase operation completely erase the block...it can be made for complete page too as page is the collection of blocks....However there is a risk of lossing a data may be you don't inteded to erase... in case if one is not sure about the erase....so for erase operation it is a general philosopy that any application used to erase the memory first ask the user for the did he is sure about erase....the best control that you can get in you go fine and fine for the control....block is that way fine control over page....so that is a reason for erase feauter mainly implemented for block and not for complete page in many Flash memories.....

I hope you got your answer....

Regards