Mayor Eric Adams, facing a major crisis that is worsening by the day, quickly appointed a new schools chancellor on Wednesday, less than 24 hours after the abrupt resignation of David C. Banks, his longtime friend.

A top deputy of Mr. Banks’s, Melissa Aviles-Ramos, will take over in January, after Mr. Banks’s resignation takes effect. Ms. Aviles-Ramos, who previously served as Mr. Banks’s chief of staff and is close with the outgoing chancellor, is relatively unknown outside the Education Department.

The immediacy of the appointment seemed intended to project stability amid the chaos engulfing Mr. Adams’s administration, as it confronts at least four federal corruption inquiries and a flurry of resignations among senior officials.

The setting of Wednesday’s news conference also seemed intended to show continuity: It was held at the Bronx high school that Mr. Banks founded several decades ago, and school superintendents and other senior education officials were summoned to attend as a demonstration of support and strength.

But it is anything but business at usual at City Hall.

Mr. Adams, a Democrat who is running for re-election next year, has faced growing calls to resign. He has insisted that he is staying put.

“I’m stepping up, not stepping down,” the mayor said at a news conference on Tuesday. “I have a city to run that I will continue to run.”