The Collaborative International Dictionary of English v.0.48:

Shallowness \Shal"low*ness\, n.
   Quality or state of being shallow.
   [1913 Webster]

WordNet (r) 3.0 (2006):

shallowness
    n 1: lack of depth of knowledge or thought or feeling [syn:
         superficiality, shallowness] [ant: profoundness,
         profundity]
    2: the quality of lacking physical depth; "take into account the
       shallowness at that end of the pool before you dive" [ant:
       deepness, profoundness, profundity]

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "shallowness":
   a little learning, absentmindedness, amateurism, appearance,
   big deal, carelessness, dilettantism, dilettantship, disregard,
   disregardfulness, distraction, emptiness, exteriority, externality,
   externalness, extrinsicality, flightiness, flimsiness, flippancy,
   fluffiness, foolishness, foreignness, frivolity, frivolousness,
   frothiness, futility, giddiness, glimmering, glimpse,
   half-learning, heedlessness, idleness, imperfect knowledge,
   inadvertence, inadvertency, inanity, inattention, inattentiveness,
   inconsideration, incuriosity, indifference, inobservance,
   lack of depth, levity, lightmindedness, lightness, manner, mien,
   negligence, nonobservance, nugacity, obliviousness, openness,
   outerness, outward appearance, outwardness, regardlessness,
   sciolism, seeming, semi-learning, shallow-wittedness, silliness,
   slenderness, slight knowledge, slightness, smattering,
   smattering of ignorance, smattering of knowledge, superficiality,
   surface-scratching, thinness, thoughtlessness, triflingness,
   triteness, triviality, trivialness, unalertness, unawareness,
   unconsciousness, unheedfulness, unintentiveness, unmindfulness,
   unobservance, unprofoundness, unprofundity, unwariness,
   unwatchfulness, vacuity, vague notion, vanity, vapidity,
   volatility