Ethereum Muir Glacier Upgrade

Pooja Ranjan
Ethereum Cat Herders
4 min readDec 16, 2019


What is the Ice Age or difficulty bomb in Ethereum blockchain?

The difficulty bomb refers to one piece of the difficulty retargeting mechanism that is built into Ethreum’s Proof-of-Work algorithm. The retargeting mechanism maintains an average block time through manipulating the mining difficulty required to mine a new block. If a block time is too short (less than 10 seconds), or too long (greater than 20 seconds) it increments the difficulty accordingly.

The difficulty bomb, separately adds to the difficulty and every 100,000 blocks it increases the value of how much it adds. At first, the amount is so small there is no visible effect on block times, and its increment is very slowly for a very long time up to a point where the increase is near exponential. This slow build-up and then suddenly “freeze” is why it is also knowns as the Ice Age.

Once the difficulty increase of the difficulty bomb is too great for the block time retargeting mechanism, it results in an increase in block times for the network. This results in a degradation in the usability of Ethereum due to waiting for confirmation for transactions and Dapps as everything takes longer throughout the network.

What changes are going into the Muir Glacier upgrade?

Muir Glacier is the upcoming upgrade in the Ethereum blockchain, subsequent to Istanbul. It is expected to be activated on the mainnet around January 01, 2020 at Block #9,200,000. The exact date is subject to change due to variable block times and timezones.

EIP 2384: Muir Glacier Difficulty Bomb Delay

Muir Glacier has only one improvement proposal, EIP 2384. This EIP will only delay the difficulty bomb for another 4,000,000 blocks, or approximately 611 days. This is the same approach we have done in the past on Ethereum. There was a discussion about changing or removing the difficulty bomb, but due to the short time frame a decision needed to be made to preserve short block times, the Core Devs decided to move forward with this simple change as we have done before and commit to addressing the Ice Age in a more permanent way in the future.

You can read more about this on the Muir Glacier Fork meta EIP 2387 and previous difficulty bomb upgrades in EIP 649 and EIP 1234.

Why have a separate upgrade, and why so soon after the last one?

The timing of when the difficulty bomb begins to kick-in is difficult to estimate. While planning Istanbul, it was first estimated that the bomb would not be noticeable until mid-2020. This implied that it could safely be delayed in the follow-up upgrade to Istanbul. However, those estimates were wrong.

The difficulty bomb started to become noticeable again on October 5th, 2019 at block 8,600,000. The average block time increased and since block 8,900,000, it is now around 14.3 seconds.

According to EIP 2384, “the average block time will start to accelerate exponentially every 100,000 blocks. Estimating the added impact from the difficulty bomb on block times shows that we will see 20s block times near the end of December 2019 and 30s+ block times starting February 2020. This will start making the chain bloated and more costly to use.”

In order to avoid a delay with the Istanbul upgrade, it has been decided to address the Difficulty Bomb aka Muir Glacier upgrade as a separate one, that only delays the Ice Age.

Muir Glacier on Testnet

  • Muir Glacier upgrade will be activated only on the Ropsten network, no other test network will deploy this.
  • It would be deployed on the testnet on the same day as mainnet. It may not be at the exact same time, but we should expect both forks within a 48 hr. window.
  • Testnet Ropsten block # 7117117
  • Difficulty bomb upgrades never activate on PoA chains — thus will not be deployed on Kovan or Gorli.

What do I need to do as a node operator or miner?

Download the following versions or later of your Ethereum client:

If you’ve missed the Istanbul upgrade and not a part of the current Ethereum chain, please upgrade your client NOW, to Muir Glacier, directly!

Muir Glacier Upgrade Countdown can be tracked at Etherscan and Ethernodes.

Shout Outs

We would like to thank Helena Flack, James Hancock , Pooja Ranjan, Tim Beiko, and the Ethereum Cat Herders who contributed to writing this article.

Thank You!!



Pooja Ranjan
Ethereum Cat Herders

Herder-in-chief @EthCatHerders, Founder @ether_world, I share news and views about blockchain technology. Ethereum.