The rifts were stable for 30 years, but in 2016, an image showed the two advancing toward each other. Scientists say the break could trigger the further retreat of the entire shelf. We’ve mapped the timeline of the split.

From the archives: In 2017, we published an in-depth look into the risk of Antarctica’s ice sheets collapsing as a result of global warming. Last year, we reported that the region was melting three times as fast as it was a decade earlier.

Here’s what else is happening

Lyft: The ride-hailing app priced its shares at $72 a pop at its I.P.O., putting its value at $24.3 billion. Its market debut was the biggest so far this year. Uber — its main rival in North America — is expected to have an even bigger I.P.O., reflecting investors’ demand for a new generation of Silicon Valley darlings that have created the gig economy.

Nissan: Once seen as a model of global cooperation, the Nissan-Renault alliance seethed with fear and rivalries. Our reporter reconstructs an environment ripe for exactly the kind of back-stabbing that Carlos Ghosn, the company’s former chairman, says brought him down.

Huawei: A British review found “significant” security problems with the Chinese company’s telecommunications equipment that governments and independent hackers could exploit, posing risks to national security. But the report stopped short of banning the company’s equipment in the country.

U.S.-China tension: The Trump administration is pushing a Chinese firm, Beijing Kunlun, to relinquish its ownership of Grinder over concerns that Beijing could use personal information on the U.S.-based app — like sexual orientation or dating habits — to blackmail or influence American officials.