In an unusual deviation from the norm, bitcoin miners just produced 16 blocks in 63 minutes, according to the Blockstream bitcoin block explorer. Four of the new blocks were mined within 46 seconds at 19:02 UTC on Friday.

Each new bitcoin block is produced every 10 minutes, on average. The exact time required to produce a new block can vary significantly and depends in part on the current mining difficulty level, which adjusts every 2,016 blocks, or approximately once every two weeks. 

Bitcoin’s anomalous spree of new blocks was first noticed by Étienne Larrivée, bitcoin developer at Satoshi Portal, a Canadian bitcoin financial services company. “Four blocks in less than a minute doesn’t feel natural, but it’s most likely only variance,” Larrivée told CoinDesk. 

Such rapid block production could signal bitcoin’s current difficulty level is too low, meaning mining new blocks is too easy. Or it could be a simple coincidence, the product of block time variability. 

Read more: Bitcoin Halving, Explained

The event coincides with a six-month high in the aggregate size of unconfirmed transactions in bitcoin’s mempool. Bitcoin transactions are sent to the mempool, which serves as a sort of holding depot, after they have been verified by other non-mining nodes in the network. Miners then take transactions from the mempool and insert them into new blocks, which are then added to the Bitcoin blockchain. 

Bitcoin’s mempool soared to 77.58 million bytes worth of unconfirmed transactions on Thursday, according to Blockchain.com.

Bitcoin’s mempool size

Source: Blockchain.com

The high number of unconfirmed transactions coinciding with such rapid block production is curious given that the job of bitcoin miners is to insert unconfirmed transactions in new blocks.

With bitcoin’s third halving less than two weeks away, Friday’s spree of new blocks could signal a significant upcoming mining difficult adjustment amidst a surge in mining power.