While the number of unconfirmed transactions recently rarely has exceeded 2,000 or 3,000 tx, on 16 July, it jumped suddenly to over 18,000 unconfirmed transactions.

According to statistical data, the bitcoin network memo began to clog sharply with unconfirmed transactions in the afternoon. At 13:21 UTC it reached its peak, with the number of unconfirmed transactions jumping to 18,531. After that, it began to fall down, also suddenly, and as of 19:00 UTC the number of unconfirmed transactions reduced to 8,281.

Simultaneously with mempool growing, average transaction fees also increased sharply. At its peak, the fee for transactions reached 1.9 bitcoins, which is approximately $12,500.

 

The blockchain congestion happened due to the fact that in the bitcoin network blocks were not mined for more than 64 minutes, whereas usually one block is mined in 10 minutes on average. For an unknown reason, the period between blocks #532146 and @532147 took more than an hour.

Users have suggested that this is due to the fact that large mining enterprises simultaneously produce bitcoin and Bitcoin Cash, and in case of more profitable BCH mining, they switch hash capacities from bitcoin to BCH.