It is difficult to construct large buildings, without a firm bedrock surface 
to build on.  Some of the largest buildings in the world are found on 
Manhanttan Island, and thus bedrock must be very close to the surface 
in these areas.  Some places in Manhattan are constructed on fill 
material or glacial sediments, and thus cannot be very tall.


1. Find a picture which shows the skyline of Manhattan (a north-south view).
2.  Using a piece of tracing paper or typing paper, trace the tops of the 
buildings, from one end of Manhattan to the other.

3. Draw a straight line (at the bottom of the buildings)  to represent the 
ground surface.4. Sketch below the ground surface what you think the 
bedrock must look like beneath Manhattan Island.