What is crust?

Famous quotes containing the word crust:

    “Under the day’s crust a half-eaten child ...”
    —John Ashbery (b. 1927)

    “All civilization has from time to time become a thin crust over a volcano of revolution.”
    —Havelock Ellis (1859–1939)

    “We shall be reduced to gnaw the very crust of the earth for nutriment.”
    —Henry David Thoreau (1817–1862)