土层

layer of soil / ground level

Tu (ethnic group) / surname Tu

earth / dust / clay / local / indigenous / crude opium / unsophisticated / one of the eight categories of ancient musical instruments 八音[ba1 yin1]

to pile on top of one another / layer; stratum / floor (of a building); story / (math.) sheaf / classifier for layers

layer filled with rammed earth in a tomb pit (archeology)

permafrost / tundra / layer of frozen soil