also: ETH is not pegged to BTC, so one can easily imagine that:

• ETH will dive considerably after something like this:
  https://themerkle.com/one-smart-contract-and-3-5m-in-ether-can-cripple-the-ethereum-network-for-a-full-week/ and/or
• BTC will rise after successfull hardfork/positive regulatory news/major hedge fund announces BTC investment etc.