It occurs either as thin beds, or in the form of thick cake-like masses, often reaching ninety or one hundred feet in thickness.
"Geology"
James Geikie
These great masses of ice attain often a great thickness, and frequently extend for many miles along the course of a valley.
"Geology"
James Geikie
The thickness of the reefs is often very great, reaching in many cases to thousands of feet.
"Geology"
James Geikie