Dogecoin jumped on renewed support from Elon Musk, adding to a volatile week for digital currencies that’s been whipped up largely by the Tesla Inc. chief executive officer himself.

After Musk tweeted on Thursday that he is working with Dogecoin developers to “improve system transaction efficiency,” the Shiba-Inu-themed token with no practical uses surged from about 43 cents to 51 cents in a matter of minutes. It’s up by about 30% in the past 24 hours, according to Coinmarketcap.com.

Bitcoin fluctuated on Friday, and was trading at around $50,500 as of 6 a.m. in New York. The largest digital token is on course for a weekly slump of more than 10%.

Tweets from the billionaire electric car CEO have roiled crypto markets this week and raised questions about his motives. Musk started the week calling Dogecoin “a hustle” and continued with a series of tweets criticizing crypto mining, which at one point sent Bitcoin down as much as 15%.

Dogecoin, which tumbled after Musk’s Saturday Night Live appearance, has now clawed its way back to being the fourth-largest cryptocurrency with a market cap of $67 billion, according to Coinmarketcap.com. Sentiment was also boosted by news that Coinbase Global Inc., the largest U.S. crypto exchange, plans to offer Dogecoin on its trading platform in six to eight weeks.

Around the same time as his Dogecoin tweet, the Tesla CEO lobbed more criticism at crypto mining following a decision to suspend Tesla car purchases using Bitcoin. Musk said that he worries about a “massive increase” in coal and other carbon-intensive energy to generate electricity needed to mine digital currency.