The volume of a cylinder is the area of the circular shape times the length (or height) of the cylinder.
Area of a circle = pi times r squared. . . Happy Pi day by the way (today is 3 14)
The diameter is 100 feet so the radius is 50 feet.
50 squared is 2500.
2500 times pi = 7854 square feet.
Now we can divide the volume by 7854 to get the height.
1,000,000 / 7854 = 127.3 feet.