If you think the crush is bad around Pennsylvania Station these days, you should have been here 465 million years ago.

“This rock has been subjected to three periods of continental collision,” the geologist Sidney Horenstein said, as he stood in a railyard west of the station, examining a wall of gray Manhattan schist with swirls of white pegmatite.

It looked like a giant marble cake. One that has broken many drill bits.

“The rock was squeezed and squeezed again and squeezed again,” he said, referring to what happened in the Taconic, Acadian and Alleghenian orogenies. These mountain-building events, hundreds of millions of years ago, shaped North America and left fascinating traces in New York City.

Some of those traces have come to light in the railyard over which Brookfield Office Properties is developing a mixed-use project, Manhattan West, beginning with a platform that will cover the entire yard.