Facebook (FB) whistleblower Frances Haugen testified in the Senate Tuesday about a trove of documents she says point to Facebook’s “destructive impact” on society that has led to, among other things, ethnic violence in Myanmar and Ethiopia.

“My fear is that without action, divisive and extremist behaviors we see today are only the beginning,” Haugen told the Senate consumer protection subcommittee. “What we saw in Myanmar and are seeing in Ethiopia are only the opening chapters of a story so terrifying, no one wants to read the end of it.”

Facebook has been blamed for helping to spread misinformation, disinformation, and hate speech that has led to sectarian violence and ethnic cleansing in Myanmar and Ethiopia.

Haugen’s testimony follows her appearance on “60 Minutes” on Sunday during which she discussed the information from her data leaks, and said that Facebook “has realized that if they change the algorithm to be safer, people will spend less time on the site, they'll click on less ads, they'll make less money.”

The Wall Street Journal initially published Haugen’s revelations in a series of articles discussing everything from the impact Facebook’s Instagram has on teens and young women to how Facebook is used by human traffickers in foreign markets.

During her Senate testimony, Haugen, who previously worked in Facebook’s Civic Integrity division, asserted that the company’s engagement-based algorithms incentivizes divisive content, since that ends up being shared more widely than non-divisive content.

According to Haugen, Facebook is aware of this, and knows that it should change its algorithms, but doesn’t because it fears doing so will mean less user engagement and result in less advertising revenue.

“The dangers of engagement-based ranking are that Facebook knows that content that elicits an extreme reaction from you is more likely to get a click, a comment, or a reshare. And it’s interesting because those clicks and comments and reshares aren’t necessarily for your benefit,” Haugen said.

“It’s because they know that more people will produce more content if they get likes and comments and reshares. They prioritize content in your feed so you will give little hits of dopamine to your friends so they will create more content. And they have run experiments on people...that has confirmed this.”

Much of the senators’ questions had to do with Instagram’s impact on teens, and Facebook’s plans for a version of Instagram for children under 13. Facebook’s internal documents provided by Haugen found that 32% of girls in one survey reported that when they felt bad about their bodies, Instagram made them feel worse.