"Death Valley, Rockefeller Center, 1933 (50th and 6th)"
This is in the centre of Manhattan and shows the remarkable bedrock which has made it possible to build skyscrapers on Manhattan island. The rock is known as Manhattan schist. Schists are metamorphic rocks;
"Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock (protolith) is subjected to heat and pressure, (temperatures greater than 150 to 200 °C and pressures of 1500 bars[1]) causing profound physical and/or chemical change. The protolith may be sedimentary rock, igneous rock or another older metamorphic rock."
from Wikipedia
This cliff face is now buried underneath the Rockefeller Plaza, so I have actually walked across it.
You can see more on a facebook page called 'Old Images of New York.'
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